I am familiar with flash photography. Much of what I shoot digitally, either in the studio or in the real world, is done with flash. On camera, off-camera, one flash, 6 strobes, no problem. I am, however, no hero. Shooting flash with digital is simple. I am good at simple things.

I would even go so far as to say that shooting off-camera flash with photographic film is also pretty simple. Between a light meter and “digital Polaroids,” transitioning from digital to film with off-camera flash was not too challenging.

Shooting film with on-camera flash is a different beast. When was asked to do an “American Apparel” inspired, edgy, rock and roll, retro, film-based, campaign for a t-shirt company, I was concerned. On-camera flash is essentially a requirement for that type of look.

In this article I cover 10 (technically 11) hard-learned lessons and provide you with overviews/crib notes of 9 (technically 10). Here’s what I cover in full:

On-Camera Flash photography is simple, right?

The complexity associated with on-camera flash in a photographic film setting is threefold:

First, the camera and model are constantly moving (or at least have the potential to move) and moving subjects require variable flash outputs.

Second, unlike a controlled studio environment, ambient light is constantly changing, and changing ambient light also requires variable flash output.

Third, and maybe most important, I am never guaranteed an assistant, so using a light meter to meter the scene and flash is not possible without putting the camera on a tripod every few frames, walking over and taking a meter reading. This interrupts the flow of the shoot like and is not an option.

Without the immediate feedback of an LCD, I was unsure how to navigate these variables in a high-pressure situation where there are no “do-overs.”

The obvious solution would be to get a TTL flash for either my Contax RX, Olympus OM-4, or Leica M7, and get on with my life but that would be too easy. I also wanted the option to shoot my Petri Racer, Olympus 35 SP, and Mamiya 7ii during the project and those cameras do not have TTL options. Moreover, I wanted one flash that would be compatible with all of the cameras for this project because I wanted to have one 35mm camera loaded with color, one medium format camera loaded with color, one 35mm with black and white, and one with some sort of gimmicky retro, light leak, film that the client requested.

For efficiency, I required a flash that could do quadruple duty and work across four different camera systems…

Welcome to the beginning

….and that is the origin story about how I began my journey into film era flashes from a time before TTL was a thing. The following are the lessons I learned.

Lesson 1: I am too stupid to use flash guide numbers in the real world

Prior to TTL and flash automation, photographers used flash guide numbers to set their camera exposure and flash intensity. A guide number is a measure of flash power: more powerful flashes have a higher guide number. As an interesting aside, if you see a flash with a number in its model name it is possible that the number is related to the guide number. For example, the Canon 580ex flash has a guide number of 58.

To use a flash guide number to calculate your flash exposure all you do is solve for the variables in the formula:

Flash guide number = Subject Distance from Flash Source x f/Stop

There are some great tutorials online if you would like to research this further but, at least for my pea brain, this all I have to say about guide numbers. I make no exaggeration when I say that I am literally too stupid to use guide numbers in daily practice.

However, I am not too stupid to understand the concept.

If you sat me down with a piece of paper and a calculator, I could get the job done, although I am just too stupid (and possibly impatient) to be doing math on the fly and/or estimate distances while I am taking photos. I am also (authentically) too stupid to even try to use guide numbers to mix ambient light with flash or accurately calculate the flash output for bounce flash, which requires estimation of the distance to the ceiling and back down to the subject and making an educated guess as to how much light the ceiling will absorb.

Your mileage with guide numbers may vary. If, however, you are as dumb as I am, welcome to the club. My gut is that we are in good company.

Lesson 2: Enter automation – auto thyristor tech

In 1972, someone decided to save the math-challenged from themselves, build automation into flash units, and give the flash the ability to turn itself off when it lit the scene properly. This technology is known as the auto thyristor flash.

The “auto” part

The word “auto” in auto thyristor refers to a photocell on the front of the flash that detects the amount of light reflected from the subject and turns off the flash when the flash detects that the correct exposure is achieved. Basically, the photocell is measuring the reflected light in the scene and adjusts the flash output accordingly. In the image below, the white arrow is pointing at the photocell.

The “thyristor” part

The word “thyristor” in the word authothyristor refers to technology that allows the flash to conserve the stored power in the flash capacitor for future exposures, which decreases the recycle time needed between flashes. Stated another way, thyristor flashes use only the amount of stored power needed for each exposure. The rest of the stored charge is saved for future flashes to speed recycle times. When used in auto mode, these old flashes have very fast recycle times.

When you turn on a thyristor flash you will hear a high-pitched, electrical, squeal:

That squeal is the sound of the capacitor charging. It might be of interest to note that when people born between the years of approximately 1972 and 1980 hear that sound, they will succumb to the crushing weight of childhood nostalgia and blather on about memories of Cabbage Patch kids, Atari Combat, Captain Lou Albano (possibly Cindy Lauper), and birthday parties where their father or mother took pictures of them. It is almost impossible for members of Generation X not to wax poetic and effuse about some such nonsense if they hear that sound coming from a flash. Try it. Fun times.

Anyway, the short story is that an auto thyristor flash is a primitive “TTL-like” flash where, even though the flash has no communication with the camera, it knows, more or less, when to turn itself off and it does so in a way that speeds flash recycle times.

It is very possible that the following comment is more of a commentary on my naïveté and bias against old technology than anything else. Nonetheless, I was floored by the performance of these flashes when I started using them. Considering their price (e.g. essentially free), I would say that I was borderline astonished. I am also astonished that bins of these flashes sit neglected in camera stores because nobody wants them. With this article, I hope to fix that.

Limitations of auto thyristor flashes

In the 2020s, auto thyristor camera flash technology is historical footnote. Although remarkably functional, the technology is limited when compared to new TTL and HSS flash units. You should be aware of these limitations before you decide whether or not auto thyristor based flash photography is for you.

Some important considerations…

Flash Sync Speed: when using an auto thyristor flash, your camera is limited to its flash sync speed. In older focal plane shutter cameras, that could be as low as 1/30 of a second (Pentax 67). 1/60 and 1/125 are also common. Some newer cameras have a flash sync speed of 1/250 sec and obviously, leaf-shutter cameras like the 500 series Hasselblad or Fuji GW690 cameras have full sync at all speeds. A discussion of how shutter speed affects flash and your image is outside the scope of this article but you should understand that you will need to shoot at or below your camera’s sync speed.

No communication = no automation: There is no communication between the flash and your camera. Your camera, therefore, can’t make any decisions or change settings based on your flash. You are going to have to input some settings into the flash and then take the information the flash gives you and manually set the aperture and shutter speed on your camera. Fortunately, this is simple.

Limited aperture options (unless you want to do a little math): your flash is worried about getting proper exposure. It is less concerned about your art and it is ESPECIALLY unconcerned about your bokeh or the fact that you are lugging around an f/1.4 lens. Most auto thyristor flashes only offer you a few aperture settings to use. There is no flash compensation. To the bokehphiliacs, you are going to have to get therapy to help you deal with your pathology and/or a set of ND filters if you want to use these flashes wide open.

Manual settings are limited with many (not all) of these flashes: these flashes all have a manual setting but, in many cases, the manual setting fires the flash at full power. Some flashes have other settings like 1/2 power or 1/4 power but options are very limited. A few of the newer flashes I tested have more granular settings.

Auto thyristor flashes suffer from some of the same issues as modern TTL flashes: The photocell can be fooled by near foreground objects that aren’t in the frame but reflect backlight into the flash. For example, if you had a mirror or window close to the camera but out of the frame, the mirror would reflect light into the photocell and trick the flash into turning itself off too early. Similarly, scenes with a lot of white (like snow scenes) may trick the flash into turning off early and underexpose the images. Conversely, black backgrounds will reflect less light and tend to over flash the image.

Issues with flash modifiers: Because the photocell is on the front of the flash, you will run into issues if you put anything in front of the photocell, including flash modifiers like umbrellas. Another situation where this is an issue is if you want to bounce the flash off of a wall behind you or to the side, if your flash head doesn’t rotate. More advanced units have rotating heads and/or sensors that can be removed from the flash and placed in the hot shoe of the camera to overcome this limitation.

Filter information is not relayed to the camera: Because there is no communication between the camera and flash, the flash cannot factor in any changes in exposure warranted if you are using a filter on the lens. You will need to manually adjust the aperture to account for a filter factor if you are using a filter.

Lesson 3: Old flash + new camera = dead camera???

Auto thyristor flash technology was introduced in an era where camera electronics were either absent, or at least less robust than the electronics used in cameras today. This is important to you because some of these older flashes employ discharge voltages that far exceed the recommendations for newer, fully electronic, cameras.

TLDR: You can fry new cameras with old flashes.

Although there are always exceptions to the rule, in general, cameras with modern electronics require flashes with a discharge voltage of fewer than 6 volts. Some of the auto thyristor flash units I tested have discharge voltages over 200 volts. Even if you couldn’t sort out the guide number math and you aren’t an electrician, you can probably understand that 200 is a bigger number than 6. You can also probably guess that if you give something that wants less than 6 volts a dose of 200 volts, bad things can happen.

Using a flash that exceeds the voltage limitations of your camera has the potential to fry, destroy, maim, kill, or otherwise render your camera nonfunctional. There are, however, simple, effective, and inexpensive solutions to overcome this limitation if your flash happens to have a high discharge voltage. We will get to those in a moment.

When I started my research, it wasn’t clear to me which flashes would cause issues with which cameras. This webpage offers some assistance but if you look closely at the chart, one take-home message is that many of these flash models were made over the course of years and some versions of the same model of a flash may have wildly different discharge voltages from another. That chart is also anything but exhaustive. There are tons of flashes that are not included in that chart. There is no simple chart or webpage to tell you which flash is safe to use with your camera.

After talking with several repair people and old timers, and after piecing together random bits of information I found scattered about the internet, I developed five rules of thumb which dictate my behavior when selecting and using these flashes. If you follow these rules, you mitigate the risk of killing your camera.

Rule of thumb #1:

If your camera hot shoe has more than one pin you have a potential issue. Before the advent of advanced electronics, the hot shoe of a camera had only one “dot” or pin. As electronics were added to cameras more and more pins were added. In the following image, the camera on the left is an Olympus 35SP with one pin/dot in the hot shoe, in the center a Minolta XD5 with 2 pins/dots, and on the right is a fully modern Panasonic S1 with 5 pins/dots.

As you can see, newer cameras have more advanced electronics and, therefore, more pins. If your camera has more than just the single dot or pin, it has electronics that have the potential to be damaged by a flash.

Rule of thumb #2:

Test your flash before you use it so you know what you are dealing with.

As I mentioned previously, auto thyristor flash voltages are all over the place — even for the same model of flash. Flash voltages are also unrelated to the size of the flash. One of my smallest flashes has a remarkably high flash discharge voltage. The following image demonstrates that the discharge voltage is unrelated to flash size.

The good news is that testing your flash discharge voltage is extremely easy. You don’t need to be an electrician or camera technician. Normal people with no experience in electronics can do this. Here is a link to a video that explains the process.

Rule of thumb #3:

Don’t use a flash with a discharge voltage greater than 6V without modification on a camera with more than one pin on the hot shoe.

As stated previously, many modern cameras are designed for flashes with less than a 6V discharge. There are exceptions to the rule but 6V is as good rule of thumb to follow.

Online you will find stories about people who got away with higher voltages but there are easy and inexpensive workarounds if your flash discharge voltage is greater than 6V. In my opinion, there is no need to push the envelope and risk damage to your camera. We are going to look at ways to modify your flash to protect your camera in a minute.

Rule of thumb #4:

Don’t be cheap. These flashes are so inexpensive, if you can afford to shoot film, you can afford to buy a few and find one with a low discharge voltage.

When you go shopping for a flash, it is very possible you will be in a camera shop with a drawer or box full of these things. Please get two or three….or four. They cost next to nothing. In my experience, if you smile a little and ask the clerk if you buy one can they give you one free or buy two and get one free they will agree. I was in one store and I asked the owner “I bet you didn’t expect to sell three of these this week?” To which he replied “I didn’t expect to sell three of these this decade” and then he threw in a few more for free without me even asking.

Rule of thumb #5:

Whatever flash you use, discharge the flash capacitor before removing it from your camera.

I was talking with a camera repair technician, a real old-timer whom I trust, who advised me that cameras get fried when flashes are removed from the hot shoe if the flash capacitor is still charged. He told me that these flashes do not fry the camera when they are in use. Rather, the problem happens if a flash with a full capacitor is removed from the hot shoe and discharges when the flash pins scrape against the hot shoe pins.

His recommendation is to discharge the flash completely before disconnecting it from the camera. To do this, press the test button multiple times and then hold it for a second or two. I was surprised the first time I did this. Some flashes have 4-5 additional charges stored up in the capacitor.

It may also be of interest to note that I was not able to corroborate his theory. I still discharge my flashes before removing them but it is possible that this is bogus and I am wasting my time discharging flashes before I remove them from the camera.

Lesson 4: It is easy to modify the flash to prevent disaster

If you are scared about flash voltages and frying your camera, that is a good thing but don’t let your fear get the best of you. There are easy and inexpensive tools and techniques to help prevent any voltage related incompatibilities between your camera and flash.

Method one

Method one: Hot-shoe based voltage reducers: Wein and Vello both make hot-shoe adapters that are designed to take the incoming flash voltage and reduce it to a voltage palatable for modern cameras. I tested both of these with a voltmeter and they both work as billed. It should be noted that the Wein product is rated to reduce the voltage from less than 400V to less than 6V while the Vello product is rated to reduce the voltage from less than 40V to less than 6V.

The Wein product is commonly mentioned as the go-to voltage reducer in the camera forums while the Vello product receives short shrift. I have a contrarian opinion. Unless you know you are going to be using a flash with a discharge voltage of greater than 40V, get the Vello product because it is designed better. The Vello voltage reducer has a screw lock that tightens the voltage reducer to the hot shoe of the camera. The Wein product does not have a locking mechanism and tends to slide off some of my cameras which is a hassle.

Method two

Flash brackets and remote triggers. The obvious solution to all of this voltage discharge business is to disconnect the flash from the camera and trigger it remotely. If the flash is not it the hot shoe or connected directly to your camera via a sync cable, it cannot fry your camera. Your only worry would be frying a radio transceiver but you can even use a Wein or Vello voltage reducer to project your radio transceiver.

The good news is that, at least at the time of writing in 2021, flash radio triggers are dirt cheap and can be had for as low as $25.00.

Not all radio triggers are created equal and the cheapest option is likely not the best. For example, some radio triggers are able to withstand higher flash voltages. Phottix radio triggers are rated to handle 300V. If you are buying a radio trigger you should consider the voltage rating of the transceiver OR just get whatever trigger system you want and attach your transceiver to a voltage reducer so it is protected.

As far as camera brackets go, I like the CB Mini-RC because it is small and portable in my camera bag. For the wedding photographer or photojournalist look, Vello makes a bunch of different brackets Some of these have the added benefit of rotating so the flash stays above your camera, which helps project the shadow directly behind your subject. In my experience, I don’t use the full-size wedding photographer flash bracket primary because I cant put the rig down on the ground and switch cameras (the camera will rest either on the lens or the back of the camera — there is no way to balance it on the base of the camera). I also don’t think getting the shadow directly behind the subject is critical in what I do.

In the image below, the camera is mounted on a CB Mini-RC bracket with:

  • a Wein voltage reducer
  • a radio receiver and
  • a radio transceiver

Method 3

Get a modern flash with old auto thyristor tech: This one is a little bit of a cop-out but if all of this business about voltages and modifying the flash to protect your camera is giving you a headache, you might decide to exit the bargain bin and explore modern flashes with auto thyristor capability. Many Nikon flashes from the 1990s and newer including the SB-30, SB-24, SB-800 (there are many) include what Nikon calls “non-TTL auto flash operation.” Similarly, the Leica SF 20 and SF 24D, are examples of modern flashes that have auto thyristor technology. Some of these modern flashes also have additional modern features like zooming flash heads and flash compensation. The trade-off with some of these modern flashes is that the menus can be (just a little) more complicated so they may obviate one of the benefits of older flashes which is the ease of use.

Lesson 5: learning about flash cables.

If your camera does not have a hot shoe (some old rangefinders only have a cold shoe aka accessory shoe) or you intend to cable your flash to your camera rather than using a wireless trigger, you are going to need cabling to connect everything together.

Given that some of these cables and connectors are no longer used on modern cameras, you might not be familiar with them. Things can be slightly confusing at first but here are the connector ends you need to be aware of:

  1. Vivitar proprietary: this spike-like nubbin is a proprietary connector that apparently doesn’t have any name other than “The Vivitar proprietary flash connector.”
  2. PC Sync male end: The female end is essentially ubiquitous on older cameras and is still found on many modern cameras. If you were wondering, the PC in PC sync stands for Prontor/Compur which was a brand of shutter on early leaf shutter cameras.
  3. PC straight connector: This connector is found on non-Vivitar flashes. Don’t get fooled. It looks like a 3.5mm connector but it isn’t. It looks like a 2.5mm connector but it isn’t. It is something different and just like the Vivitar proprietary connector it doesn’t seem to have a name other than a “PC straight connector.”
  4. 2.5mm connector: This is a modern connector that you are going to find on some wireless triggers.
  5. 3.5mm connector: This is a modern connector that you are going to find on some wireless triggers.

If your flash comes with a cable it is a good bet that it will have either a:

  • A Vivitar proprietary connector on one end and PC sync connector on the other end OR
  • A PC straight connector on one end and a PC sync connector on the other.

An easy and straightforward method of getting configured is to take that cable and plug it into the PC sync port of your camera (assuming the flash has an output voltage of less than 6v) or the PC sync port of your voltage reducer.

Of course you can always just put the flash in the hotshoe of your camera. To protect your camera you can also always stack it on a voltage reducer in the hot shoe of the camera.

Things get marginally tricker if your transceiver doesn’t have a hot shoe or your flash is mounted to a handle like the Sunpak AP-52 “potato masher” discussed below. In either of these cases, you are going to have to find a way to get one end of your connector to be a 3.5mm or 2.5mm connector because that is what is found on radio triggers. In this situation, you would need either a Vivitar to 3.5mm cable or a PC straight connector to 3.5mm cable and stick the 3.5 mm end into your transceiver.

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Lesson 6: Configuring and using an auto thyristor flash

Now that your flash is attached to your camera or a remote trigger, it is almost time to make magic. First, you get to learn how easy these flashes are to set up and use.

The main thing you need to understand about these flashes is that they are going to shut themselves off when they determine that they have given you enough light for a proper exposure. You will not be doing any metering. During setup and configuration, therefore, your job in setup is to tell the flash how much light is enough and set your camera accordingly. It takes about 11 seconds. Yes. It really is that easy.

The setup is almost exactly the same on each of them. Some flashes have a dial you turn, some have little switches, some have a table you need to read, newer ones have an electronic interface. If you can figure out how to open a can of soda, load film into your camera, and/or pick your nose, you can do this.

Step 1: Set your camera to your camera’s flash sync speed or slower. On most cameras, there will be one number on the shutter speed dial that is a different color or has a lightning bolt or something to tell you that is the sync speed. Pick that one.

Step 2: Enter the ISO of the film you are using in the back of the flash

Step 3: Find the slider or lever with different colors to set the distance between your flash and your subject and pick your aperture. Every manufacturer uses different colors but on this slider, there will be one option for M (manual) and two or three other positions with different colors. These colors correspond to the subject distance and aperture setting. If your subject is close pick the close option. If the subject is far, pick the far option. This isn’t brain surgery. Don’t get all worked up and overthink the flash distance. There is a HUGE overlap in the near and far range. You can be off by several feet and they will still work fine. The overlap in distance also affords you the option of two or three different apertures. If you are in the overlap zone pick the one with the f/stop you want to shoot. NOTE: If you are going to use a bounce flash off the ceiling, select the far option.

Step 4: Once you do all of that, note the f/stop you picked on the back of the flash and set that on your lens.

That is all there is to it.

It might be of interest to note that the ISO slider doesn’t actually do anything to the flash output. The ISO slider is really just a fancy lookup table that changes your aperture options when you change the ISO slider. Some flashes don’t even have an ISO slider. They just have a table on the back and you need to read it on your own.

Conversely, the distance slider does affect the flash output.

Lesson 7: My experience. Use cases and contraindications.

My experience with auto thyristor flashes has been overwhelmingly positive, They are extremely easy to use and do what they are designed to do BUT only if you know when to use them and when to leave them at home and use a different tool.

DO use auto thyristor flashes on camera at night, in the shade as fill flash, and indoors: these are the use cases where these flashes excel as either direct or bounce flash. My assumption is that they work well in these situations because the photocell is able to accurately measure the light reflecting off the subject.

Consider NOT using auto thyristor flashes in auto mode when outside or in bright sunlight. In my experience, these flashes have variable performance in full sun or backlit scenes. My assumption is that they fail because the photocell can’t accurately judge the amount of light reflecting off of the subject in these brightly lit situations. Another issue is that your flash sync speed will be too low to obtain a proper ambient exposure without using a very small aperture and many of these flashes are not powerful enough to light a scene at very small apertures. To use these flashes outside in the bright sun you would need an ND filter or a camera with a leaf shutter camera, and a high guide number flash. We will come back to the topic of leaf shutter cameras in the section about “day for night” flash photography.

Be very selective in choosing/using auto thyristor flashes in manual mode as off-camera flash: The reason for starting this deep dive into auto thyristor flashes was that I needed a flash I could use without metering a scene. With off-camera flash, your flash is untethered to your position. There is nothing stopping you from walking up to your subject….taking a meter reading…. and using manual flash settings. Although there are exceptions to the rule (including many newer Nikon speedlights), many of the older, legacy, auto thyristor flashes don’t have adjustable manual power flash settings; and if they do there aren’t all that many manual setting options. Therefore, if you are looking for a flash to use primarily as an off-camera flash and you will be metering a scene, I would encourage you to be selective, avoid the older, legacy units, and get a more modern speedlight with a wider variety of manual settings.

Also be very selective in choosing/using auto thyristor flashes off-camera, in auto mode, if you intend to put them behind a softbox, in an umbrella, etc. Remember, the photocell on the front of the flash reads the light in the scene. If it is behind an umbrella this won’t work. Some of the more professional units have removal photocells you can mount on the hot shoe of a camera but, as a general rule, there is better technology to use off-camera with a light modifier in front of the flash.

DO NOT use auto thyristor flashes in auto mode in a group with other flashes. This is a non-starter. The flash from one flash will interfere with the photocell of another flash and turn it off. These flashes are like the betta fishes of the flash world. They prefer to live alone. I tried it. It was a waste of time.

The bottom line is that, in my experience, auto thyristor flashes are best used on camera, at night, or indoors. There may be better tools for flash photography in other situations.

Lesson 8: Hacking auto thyristor flash settings to simulate flash compensation

Modern flashes and cameras have flash compensation settings that allow you to dial-up (or down) the amount of flash in your image. auto thyristor flashes don’t. They are one-trick ponies that shut themselves off when the photocell detects a proper exposure. It is important to note that:

  1. A proper exposure is subjective, and
  2. The photocell doesn’t communicate with your camera

It doesn’t know how much light is hitting the film. It cannot stop you from giving the film more or less flash than the photocell thinks is appropriate.

If you want more flash in your image than the photocell deems necessary, you can just open your aperture (e.g. use a smaller number f/stop than the flash recommends). In my experience, going further than about one stop tends to overexpose the subject too much. Conversely, if you want to give your film less flash than the photocell deems necessary just pick a higher aperture (e.g higher number).

Lesson 9: “Digital Polaroids” and testing before you try to make images of consequence.

In the film photography days, photographers would take a Polaroid to test their settings prior to taking actual images with their camera and flash. You should too.

I know I am going to run afoul of the film purists with the following recommendation but the fastest way to become proficient with flash if you are new to flash and/or simply to test your flash if you are unfamiliar with your particular unit is to put your flash on a digital camera and take “digital Polaroids.

In my experience, each of these flash units should be treated as an individual. Some, at least to my taste, slightly underexposed, some slightly overexposed, and some are on point. You would be well served to get to know your flash prior to using it on a live shoot or in a situation where the images are of consequence. By practicing, you get a feel for when you should add or subtract flash using your aperture setting as decided in Lesson 8.

Lesson 10: Learning to shop for an auto thyristor flash

There are too many models of auto thyristor flashes to even attempt to offer you a “Top 5 list of the best auto thyristor flashes of all time” recommendation. Truth be told, I have no idea what those 5 best are or even if there are even 5 best.

Rather than a top 5 list, I am going to analyze 8 flashes and describe why I kept or discarded them. By understanding my thinking, I am confident you will be able to choose your own when confronted by a box or drawer of them in your camera shop, on eBay, KEH, or shopgoodwill.com

Ultimately, all of these flashes do about the same thing and, with a few exceptions, they seem to be interchangeable as far as I am concerned. The main differences between these flashes are related to:

Flash discharge voltage: this was discussed previously. Ideally, you want a flash with less than a 6V discharge but many are higher. You already know that you can use a voltage reducer or wireless trigger to overcome any voltage incompatibility with your camera but why not just get one with a low(er) voltage to help prevent issues in the future?
Flash size (guide number/output and ergonomics): If you are using your flash at night and indoors you probably don’t need the biggest flash. Moreover, larger flashes are unwieldy sitting there perched atop a small camera. I prefer flashes with a guide number in the range of 25-30. Bigger than that are unwieldy and are not necessary for what I do. Smaller than that, they lack power or may have slow recharge times. If you are going to be bouncing flash off the ceiling you will need a higher power unit.

The number of hot shoe pins: the functionality associated with hot shoe pins is irrelevant for our discussion. Nonetheless, when shopping you should take note of the number of hot shoe connector pins on the bottom of the flash. More advanced flashes have more pins and were, therefore, designed for newer cameras. One trend that I noticed when I was doing my testing is that flashes with more connector pins — in general — have lower discharge voltages. This is not a hard and fast rule (e.g. you still need to test your flash and there were exceptions in my testing) but getting a flash with more pins might be a quick and dirty method of picking a flash out of a pile of flashes with hopes that it will have a lower discourage voltage. Remember, you still need to test your flash to know what you are dealing with. Some of the flashes with 5 pins still had discharge voltages incompatible with modern cameras.

Confidence light: some units have an indicator to tell you that the subject is reflecting enough light to stimulate the photocell and allow the photocell to give you an accurate exposure. On my Sunpak units, there is a light that says “auto OK” that flashes telling me I am good to go. Importantly, the confidence light lets you test the flash before you press the shutter to make an exposure. If the light does not come on, you can use a larger aperture or go closer to your subject and do another test. In my opinion, this is a critical feature that lets me know if I have a good chance for success using the auto thyristor to determine my exposure.

Remote sensor: Some flashes have a sensor that allows the user to take the photocell off of the flash and place it in the hot shoe. This helps guarantee proper exposure because the camera is always pointed at the subject while the flash doesn’t necessarily need to be pointed at the subject. This feature also allows you to put the flash behind an umbrella, pointed bedding your for bounce flash etc.

Bells and whistles like a rotating flash head, zoom head, ports for battery packs, etc: some flashes are more fully-featured and others are bare-boned. Ancillary features abound but these features are probably not going to be the deciding factor for you if you are looking for a basic flash.

Vivitar, Sunpak, and Metz: These brands were common during the heyday of the auto thyristor flash in the ’70s and ’80s and you will encounter these names when you shop for auto thyristor flashes. All three brands sold flashes that catered to different budgets with varied functionality but, as a general rule, Metz was considered to be more robust and geared toward advanced amateurs and professionals. The Metz 32, 36, 38, and 45 series were well regarded. There is some discrepancy among those who were shooting at the time but after talking with about a dozen contemporaries I don’t have a feeling that between Vivitar and Sunpak there was one brand that was clearly superior to the other. The Vivitar 283 and 285 are classics. Similarly the Sunpak Auto 36DX was common. In my hands, they have similar functionality and seem to be of similar quality. There were, however, many other types of flashes and, as you will see, you are encouraged not to limit your options to these three manufacturers.

  1. Vivitar 283 and 285
  2. Minolta Auto 132X
  3. Vivitar 2000
  4. Vivitar 2800
  5. Fujica Autostrobo 300X
  6. Sunpak Auto 433D
  7. Vivitar 500FD
  8. Leica SF 24D (also SF 20)
  9. Nikon SB800

1) Vivitar 283 and 285

If I were a betting man, I would bet that if you didn’t read what you are about to read, you would go online and order yourself a Vivitar 283 or 285 flash. How do I know? Because you are me and I would have done the same thing. You would do some reading and learn that Bruce Gilden uses one of these. You will also learn that the photojournalist big boys used these back in the day. I know that your gut reaction will be to go retro and get the most famous flash of its time. My recommendation is to reconsider. In my opinion, the Vivitar 283/285 is something along the lines of the YASHICA T4 of flashes. It gets all the hype but is that hype is tough to justify a purchase in 2021?

I have one. It is nifty. It makes me feel all hipster and retro and warms the cockles of my heart when I tell myself I am a real true photojournalist from the ’80’s but I have never used it other than for testing. I am afraid of it. The discharge voltage of my copy is a whopping 245 volts. In my opinion, there are too many other options out there to be messing around with this 245 volt monster. It is also massive. Putting one of these on a diminutive Olympus camera or a leaf shutter rangefinder is unwieldy and, at least in my opinion, a vulgarity of poor taste.

Before we leave the topic of the Vivitar 285, there is a modern version called the 285HV with a lower output voltage. At least one resource mentions quality control issues https://www.slrlounge.com/vivitar-285hv-review/

2) Minolta Auto 132X

This little beauty is a perfect size and has a guide number of 32 which is larger than I would expect for a flash of this size. I include it here because 1) I kept it and 2) it has a dial on the back rather than the more common table to remind you not to be afraid of dials and 3) it has a discharge voltage of 2.33V.

3) Vivitar 2000

This flash is tiny. I thought it would be perfect for my Olympus 35SP but guess what? The discharge voltage, even though this flash is ridiculously small still discharges at a whopping 220V. Do not assume small flashes have low discharge voltages. There is ZERO relationship.

4) Vivitar 2800

Another tiny Vivitar flash with a large (143.6V) discharge voltage. This is included to remind you (again) that there is zero relationship between discharge voltage and the size of the flash.

5) Fujica Autostrobo 300X

The discharge voltage is only 5v. With a guide number of 30, it is too big to match nicely with my smaller rangefinders but for the Contax RX it is a great fit. This particular flash also has an extra trick up its sleeve. On the front, there is an extra fill flash that only activates if you are bouncing a flash off the ceiling. It works great. This one has a dial on the back. Remember, do not be afraid of flashes with dials. Finally, this flash has three different distance ranges (and aperture options) rather than the more common two. Unfortunately, the aperture/distance control is on the front of the unit which is annoying. This unit is included in this round-up to remind you to look at brands other than Vivitar, Sunpak, and Metz.

6) Sunpak Auto 433D

This flash has some more bells and whistles than others in the roundup given that this flash has 5 manual settings (full, 1/2, 1/4, 1/8, and 1/16 power). It also has an AUTO OK/confidence light. Finally, it has a rotating head for bounce flash so the photocell can face forward while the flash is pointed sideways or back. Hands down, this is the most full-featured flash of all that I tested. The downside is that the discharge voltage is 7.64V. Given the multiple manual control settings and the confidence light it is my favorite of the legacy flashes I tested. If I could find one with these same features and a lower discharge voltage, I would have my ideal legacy auto thyristor flash.

7) Vivitar 500FD

I had little luck with Vivitar. This flash is a great size but with a discharge voltage of 6.56V it was right on the edge. The first issue was that the mechanical table on the back didn’t work right. I couldn’t see the f/stop number for the far setting. The second issue is that the photocell wasn’t fully functional. Maybe the photocell was broken? Maybe some kid stuck a pencil in the photocell? Whatever it was, it routinely gave too much flash. I include this flash in the list to remind you that you need to test your flash, and when you are shopping get a few if you can. These are old units and most of them have been sitting in a drawer somewhere.

8) Leica SF 24D (also SF 20)

Normally I would not recommend Leica anything to anyone that is not invested in the Leica ecosystem but I do happen to run leicalensesfornormalpeople.com so you can probably guess that I bought one of these. I am, however, not a full-time fanboy. Unlike anything else from Leica, however, these go for a fairly reasonable price (~$150) used. The reason I bought it is that it is tiny, it is essentially flat, and just like the auto thyristor flashes, discussed in this article, it has a photocell and functions similarly to all of the other flashes. It is a perfect size to leave in my camera bag and, given that it is a modern flash, I don’t need to worry about discharge voltage. It is relatively low power and is not appropriate for bounce flash but it is a great option if all you want/need is a tiny flash for fill. You are permitted and possibly encouraged to cover the word Leica with gaffers tape. Nobody will know.

9) Nikon SB800

Go Nikon! Nikon has been quietly including photocell technology in many of their modern flashes. Even though most of the features of the Nikon flashes are overkill for what we are discussing here, they are fully functional in the manner we have been discussing. Nikon calls this functionality “non-TTL auto mode.” This flash also works on any aperture and is fully functional as a manual flash with a wide variety of manual settings. Finally, it offers a zoom feature to match the flash spread with the focal length of your lens. The only downsides are price and with an electronic interface these flashes have a slightly longer learning curve than the legacy auto thyristor flashes.

BONUS: Sunpak AP-52

The “potato masher” or “hammerhead” style flash was popular among wedding photographers and photojournalists. This style of flash is known for a higher guide number/output than hot shoe mount flashes which allowed the photographer greater access to bounce flash techniques. Back in the day, high-power flashes were more important because photographers often used lower ISO film such as ISO 64 or 125. Additionally, with large, handles, and quick release brackets, they are also designed for off-camera, use. Finally, many of these units were more fully featured for the professional photographer including more options for different apertures than hot-shoe mounted units.

This particular unit will run on 4AA batteries. Traditionally, “potato masher” flashes were used with external power packs for increased power and decreased recycle times.

Although “potato mashers” were the choice of the pros back in the day, I am not sure that this is the best option for most casual film users in the post pandemic era because most of us wont be carrying around external power packs, we don’t need ultra-fast recycle times for dozens and dozens of exposures, and space in any camera bag is limited. Nonetheless, if you need something powerful, these are an option.

One downside, at least for my feeble electrician skills, is that I could not sort out how to test the output voltage since there is no hot shoe. Perhaps it doesn’t really matter since you will need to cable the flash to your camera in every situation so you can just cable it to a voltage reducer.

It may be of interest to note that I pulled out the “potato masher” on a shoot and it won a fair number of style points. It may also be of interest to note that things are not all that much different from 1978 when the New York Times commented:

“…In addition, I /strongly suspect that another reason for the current popularity of handle‐mount strobes lies in what might best be described as “photographic chic.” Photography has become, like tennis, a national mania, and just as many a novice tennis player buys an expensive racquet to emulate the celebrated pro whose name adorns it, so does many a budding photographer purchase a “professional” flash unit whose full capability he may never use.”

New York Times, January 8th 1978

Again, these flashes are probably overkill for most of us but if you are looking for style points, the “photographic chic” bonafides of a “potato masher” flash will, at a minimum, create conversation and allow you to bounce light behind you or off the ceiling in a convention hall like a pro in 1982.


My retro, rock and roll, inspired shoot was successful. The auto thyristor flashes performed splendidly. Moreover, after doing the research for this shoot, I have a new approach to flash. I am essentially done with TTL for anything other than my commercial setup which is a Sony/Profoto combination. I decided to keep the Leica SF24-D and the Nikon SB-800 for daily use.

I am, unfortunately, unable to share the images from the shoot I was preparing for but these images are from a different day I used as a test. Keep in mind, this on-camera flash, rock and roll, hard light look isn’t for everyone and it certainly cant be used on every subject. The principles behind these auto thyristor flashes, however, is what is important.

When I shot these images I didn’t meter or worry at all about flash settings. It would be just as easy to bounce these flashes into a reflector off camera, off of a ceiling, or use one of those dome reflectors to soften the light but learning to make your on-camera flash look more flattering is a story for another time.

Bonus Lesson: Taming sunlight with a leaf shutter camera and creating“day for night” flash photography.

In Lesson 7, I said that using auto thyristor flashes during the day isn’t ideal. The reason is two fold. First, I am not certain that the photocell is able to accurately gauge the light reflected off of the subject in full sun. Second, the sync speed of many film cameras is relatively slow at 1/50, 1/60, or 1/125.

The slow sync speed is an issue because if you are shooting at relatively slow shutter speeds you are going to need to use a high aperture (and/or very low ISO film) to get a proper exposure. This is an issue. There is a rule of thumb in photography that shutter speed controls ambient light and aperture controls the ambient light and flash. https://strobist.blogspot.com/2006/03/lighting-101-balancing-flash-and.html. Knowing that, as you increase your aperture you would need more power from your flash to have the same effect on the image. Unfortunately, unless you have a “potato masher,” these small flashes are not powerful enough to overcome very high apertures in bright light.

All, however, is not lost. A leaf shutter camera will allow you to use flashes during the day. An ND filter would also work but I find ND filters to be a pain to use.

Leaf shutter cameras sync at all shutter speeds. For example, my Olympus 35SP and Mamiya 7ii sync at any shutter speed all the way to the top shutter speed of 1/500 sec. This means that I can meter a scene at the recommended aperture setting for the flash and then set my shutter speed accordingly. As an example, this is a day-for-night test using my Olympus 35SP and Koda T-MAX 400.

The first image was taken without flash. Using that same exposure, I simply darken the scene by two to three stops using the shutter speed dial (e.g. use a 2-3 stops faster shutter speed). I then consult my flash and set it to whatever aperture is highest (on this flash I think it was f/8) and use that aperture to take the image. This will darken your background and keep your subject exposed with a darkened background simulating a nighttime image.


Auto thyristor flashes offer you primitive but highly functional, TTL-like, flash metering across camera manufacturers that allow you to focus on taking an image and not worry about flash output. They are an excellent and inexpensive way to add flash to your film arsenal. In my opinion, every film photographer should have at least one in their kit.

Older TTL flashes may have high flash discharge voltages that can fry modern camera electronics. Hotshoe voltage reducers and wireless remote triggers are simple, easy, and effective workarounds that will protect your camera.

All of these flashes do about the same thing. Get one with a less than 6V discharge rating that is of a proper size for your camera and needs. Since you will likely (at least at first) be using them at night, you don’t need the biggest flash. A guide number of 25-30 is adequate.

Auto thyristor flashes are best used at night, indoors, in the shade, and without flash modifiers. Flash modifiers require removable photocells that are only found in more expensive, professional, units.

The Vivitar 283 and 285 flashes get all the hype but I caution you to be smarter than a sheep following the herd. They are enormous beasts and the discharge voltages are very high. You now know better unless, of course, for some reason you want an enormous beast with a high discharge voltage.

I have all sorts of modern flashes including Profoto, Sony, Canon, and Contax flashes. If, however, I want a tiny flash, I am shooting at night or inside, and I am not using a camera that supports TTL on a flash I own (including my Olympus 35SP, Olympus Pen FT, Olympus Om-4, Petri Racer, Maimya 7, and Minolta XD cameras) I will grab an auto thyristor flash and not think twice about it.

As I mentioned before, after writing this article I even went out and bought myself a Leica SF 24D so I could use one without any worries about voltage issues, voltage reducers, etc.

Thank you to Will Prentice of Amplis photo for information regarding the history of Metz Flashes, Forsters Camera SLC, Acme Camera SLC. Thanks to people with avatar names I don’t know how to credit in various photography forums, and members of the Film Photography Chat Facebook group for some ideas and background information for this post including Anne Greaves DeCristoforo, Richard Hardwick, Spike Brown, Janet Kopper, Eddy Did, Brendan Delaney, Jimmy Peters, Dante Stella, Steven Mitchell, James Hanes, Timothy Anderson, Gary Padgett, Gary Miller, Paul Gray, Will Spiers, Jon Williams, Oguz Erel, Reuben Zauzua, Douglas Elick, Michael-Joseph Wade, and Ray Bourgeois.

I could have started this article by telling you it was close to 10,000 words in length but honestly, I didn’t want to put you off. If you managed to get this far and have decided to try flash photography for the first time, film or digital, my job is done. If you are now beginning to think about it for the first time, then I consider that a job well done, too. Demystifying things like this is important but not always SHORT!

If you have any questions, please let me know in the comments below! Find me @themattwphoto.

~ Matt

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Avatar - Matt Wright

Matt Wright

I am a part-time photographer working in San Diego and Salt Lake City, USA who, after backpacking through Southern Africa in the late 1990's, carrying too many rolls of film, wrote off film for good only to return several decades later at the urging of a very...

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  1. Thanks for taking the time to write this extensive and entertaining article. Just like you I own several of the old Thyristor flash including the Vivitar 283/285 The metz 45CT, The Metz 50 MZ5 and the Metz 70. Ironically I sold my Metz 76 ETTL because it was not reliable. I then purchased a Quantum TD-R5 with TTL and Auto Thyristor technology. One thing to remember about these flash units, is that light is light and that never changes.

    So if you think a more modern flash is going to give you better light, forget about it. What will give you better light is ususally the size of the flash head. Smaller flash-heads like the built in pop-up flash on your camera will produce harsher light no matter how many gadgets you put on it. The thing that got me on the Thyristor flash bandwagon was that I noticed that they consistenly outperformed my more sophisticated eTTL and iTTl flash units. The word is CONSISTENCY.

    Also due to their large flash-head(on some), you get softer wrap-around type(almost studio) lighting. Altough some speed flash units like the top Canon and Nikon brands have improved significantly in the past few years, when it comes to consistency and/or wrap-around lighting, I still say the Auto Thyristor units come out on top.

    Unfortunately, nobody wants to be seen with these older flash units anymore, especially at a wedding or special events. “Uncle Joe” sitting in the Isles of the church with his mirrorless camera would probably die laughing. However, I still bring my Metz 50 or 70 to weddings for large group shots and even not so large. The light just looks better.

  2. Hey, nice overview of the auto thyristor style flashes. One point I would add is that the 7V trigger voltage Sunpak flash should be completely fine with any modern digital camera. Check your manufacturer’s specs to make sure.

    I’ve been using that style Sunpak flash with digital and film cameras for years. My favorites are the Sunpak 444D, 30DX, and similar Sunpak hotshoe style flashes. They have a wide range of manual and auto settings with tilt and swivel heads. For a potato masher/hammerhead style flash I use Sunpak 555 flashes– they have about twice as much power and have a very wide range of manual and auto power settings.

    I agree with Robert about using manual power settings. Sometimes you want to have a consistent flash power and the manual modes have a calculator built into the sliders that show you what f-stop to use at what distance. Bouncing the flash off a white wall or ceiling complicates things though. If you put your flashes on light stands, maybe with modifiers, and your subjects stay in the same place, manual mode is the way to go.

  3. Excellent article. I use since 2008 my old Metz 60ct2 flash, 8v voltage output, my vivitar 285 and 283 made in CHINA with 8v output, and my Metz 45ct1 with 40v output (I use it with Phottix radio) and Metz cl3 with 6v output . And even an old 200v Mecablitz 402! With the exception of the 402 and the Ct1 which I only use with radio, the other flash I always connect them to Pc syncro of the camera. Jama I have mounted on the camera no flash, old mania that I have since the days of 35mm. I have consulted with Canon and they have confirmed that on hot shoe they only support 6v but by pc syncro cable they support up to 200v. Even the Metz technicians have confirmed to me that I can use by pc synchro all the metz that I have except the 45ct1 and 402. I know that Nikon on its hot shoe supports up to 200v. At 283-285 I use them with a 6v and 4 ah SLA battery, giving me great autonomy in events. The Metz 60ct2 I also use it with SLA 6v 4ah. Infinity of shots. I have never returned to AA batteries for more than 10 years. It is a pity that the current digital cameras do not have the Pc syncro connection. Greetings from Buenos Aires!

  4. Lots of interesting stuff here. I would make a couple of comments though. One is that “thyristor” is/was used loosly in the flash world, including by the marketing people. The first Auto units did not use thyristors they cut off the flash at the right moment by dumping the rest of the charge to an internal flash tube with an opaque coat. When the thyristor was introduced it was able to divert the current into a small capacitor which extinguished the flash tube without much wasted charge. The non-thyristor type had to re-charge from scratch each time.
    As for the Guide Numbers, there is no need to avoid manual mode because you don’t want to do the maths. I have never seen a flash unit with a manual mode that does not have some sort of look-up table or a slide calculator on it to save doing maths. I’m guessing that ones with digital displays have an internal calculator too.
    Lastly, you are a bit dismissive about swivel/tilt heads, but keen on detachable sensors so the flash can be pointed differently from the camera – the purpose of swivel heads. Myself, I would not like to hold my camera in one hand and the flash in the other – although I’d have a strap on the camera in case I dropped it, I would soon get wrist ache.
    To measure the trigger voltage of a hammerhead unit, you simply put the voltmeter probes on the sync lead plug. Touching on the centre contact of the little co-ax plug is slightly tricky, but pefectly possible.

    1. Actually, there is an easier, and safer way to measure the trigger voltage and that is to use a a PC to Hotshoe adapter. Measurement is then taken across the terminals of the hotshoe. These useful adapters are not as common as they once were, but once you have one it can easily be used to test any flashgun you’d care to mention.

  5. This is a pretty good coverage of some of the many complexities of strobe flashes and I’d definitely recommend it to beginners. There are two point though, I think are worth addressing. 1) you list a few common flash connectors, but you’re missing 3. The “bi-post” connector used on older leaf shutters and graflex cameras, the “household” type 2 prong connector used on older flashes equipment like the sunpak strobes and powerpack type strobe systems, and the asa bayonet which is on older American leaf shutters, which is often easily adapted to the PC type connector. The other comment worth relating, is most photographers didn’t do guide numbers on the fly: they took the film they were using, and the guide number of the strobe or flashbulbs they were using and they computed a little chart on notecards, and taped them to the back of their camera with the distance and aperture combinations they would need for that particular task. I’ve wound up with a handful of old speed graphics and graflex SLR’s with these little handmade tables stuck to them, and there is a certain soundness to the excecise if you have the guide number for a manual flash and are willing to spend the time calculating. (And most lenses and rangefinder cameras will tell you the distance to subject on the focusing scale of the lens.

  6. Great article – very thorough. Sounds like you learned a lot! Don’t be fooled, though – only serious amateurs and above really understood auto-thyristor flash back in the day. Most people who were shooting 35mm “set to auto”, which wasn’t too tricky once you’d done it a few times, but I’m not sure most folks understood how it worked, unless they’d had a photography class or were serious hobbyists.
    I didn’t realize those old flashes that were so commonplace back then were anything special. It was neat to see them rediscovered in your article! Thanks for sharing your story and your experience!

  7. Are, the good old days when we didn’t have to worry about electronic flash guns frying our camera’s electronics, and thus it wasn’t necessary for the trigger voltage to be quoted in the spec.

    Having used bulbs before getting my first electronic flash, purely manual, moving to my first thyristor unit, the Vivitar 283, was so enlightening. No more calculating f numbers and taking into account ambient lighting or reflective walls/ceilings, the sensor did (most of) the hard work.

    With so many third party manufacturers, the safest option today would seem to be to use a flashgun from your camera manufacturer but even this may not be suitable for the electronics of digital electronics if it preceded them.

    You referenced the so-called “hammer head” units, but these were far better to use with TLR cameras, many of which didn’t incorporate an accessory shoe. Hammer heads provided the necessary grip and also moved the flash head further away from the lens axis, thus minimising red eye.

    One small point, if I may. “Trigger” voltage and discharge voltage are not the same thing. Discharge voltage should refer to the high tension voltage used to fire the xenon tube. This is provided by the capacitor and the voltages produced can indeed give quite a kick if one somehow comes into contact with one that has not been discharged.

  8. Very enjoyable article. I immediately tested the trigger voltage of my guns. One gun that served me well profesionally is the Sunpak Autozoom 3000, trigger voltage of 195. It has a range of 4 auto settings and 6 manual settings. The lowest manual setting allows high speed photography, I shot the old milk drop into a saucer with this flash.