If you’re reading this guide, you’re probably new to RA-4 colour printing. Don’t worry, until recently, so was I. Over the past few months, I have spent a lot of time finding information about and practically learning the process. Since what I needed was scattered around the internet in small bits on different websites, forums and blogs, I decided to collect all that information together and make a simple guide to help get people started with colour printing.

Ra-4 Prints
Ra-4 Prints

I must say that this article assumes that you already make your own black and white prints, so I will not cover the basics of using an enlarger. If you are completely new to darkroom printing, I suggest you start with black and white, since the RA-4 process is a bit more complex.

Here’s what I cover in this article:

Colour vs black and white darkroom printing

Some people don’t print their colour films in the darkroom because they’re scared about the complexity, but it’s not as horrible as you might think. Aside from the need for a dedicated colour lamp/head for the enlarger, colour darkroom printing differs from black and white darkroom printing in the following respects:

No contrast correction
With black and white papers, contrast is variable thanks to colour filters. Since we are already using colour, that is not possible. What you have is what you get.

Filtering with colour
You need to know the primary colours and complementary colours (see further below). It sounds complicated at the beginning, but it’s only six colours. Everyone can remember six colours.

Different chemistry
The colour printing process for negatives is called RA-4, and you have to buy a kit of chemicals for this process. Apart from that, you have to get your prints to the different baths at the temperature and time indicated, just like you would do with black and white.

Needs temperature control
You must keep your chemistry heated between 30ºC and 35ºC. You can do that with a simple tempered bath. It’s not as simple as black and white, but not as complicated as developing colour film, where you have to keep your chemicals exactly at 100ºF or 37.8ºC.

You need Complete darkness
Colour papers have to be used in complete darkness, as they are quite sensitive to light. This was the scariest part for me, but when I tried it, I found out it was quite easy. You already know how to use your enlarger, you know your lab. It’s a matter of organization. Know where everything is placed at all times and you’ll be just fine. If you don’t believe me, try switching off the safe light of your black and white darkroom, take your paper out of the box and expose it. You can switch it on again before putting the paper in the trays (you probably won’t be using trays in colour). Was it that bad? With colour printing you only need complete darkness during very specific parts of the process, and it’s way simpler than you imagine.

These differences complicate everything, sure but wasn’t black and white complicated when you first started? You challenged yourself and you can do it again. I hope that this guide opens new opportunities for you, but mostly I hope you enjoy the process.

Don’t worry about failing. Trying and failing and succeeding is the beauty of this process, so enjoy every moment of it.

RA-4 development methods

You have four options open to you for RA-4 processing as follows:

Option 1: Open trays
The whole process has to be conducted in complete darkness, which makes this method the most complicated one. You’ll need to have a clock that doesn’t glow enough to burn the paper and a lot of chemistry is needed for this variation of the process.

Option 2: Daylight film tank
The advantage of this method is that once the paper is inside, you can do the rest of the process with the lights on. Also, you need way less chemistry compared to tray development (as little as 200ml).

The disadvantages are:

  • You have to be really fast pouring the chemicals, as you have to put it as horizontal as fast as possible.
  • Most of them don’t roll flat, so you have to roll it with your hands.
  • You have to make sure the central part of the tank (the one that usually holds the spirals) is correctly positioned, or else you might have a light leak.

I must say I did my first prints with a film tank with no problems.

Option 3: Paper drum
The advantages of this method over the others are:

  • The chemicals are not poured to the paper until the drum is put in horizontal.
  • You can use a small quantity of chemicals, with some needing as little as 60ml.
  • You can rotate it easily on a flat surface or a roller.

Option 4: Rotatory processor
…such as a JOBO. This is the most expensive way, but also the one that will give the most consistent results. It keeps the chemicals and the drum at the correct temperature and rotates at a stable speed.

RA-4 required equipment

Kit list

The equipment required for RA-4 printing is similar to what you should already have for making black and white prints. Of course, the main difference is going to be your need for a colour enlarger such as the Durst M605 I’ve been using.

Here’s your basic kit list:

  • A colour enlarger
  • RA-4 Paper
  • RA-4 Chemical Kit
  • Acetic Acid to prepare your stop bath
  • A thermometer (I recommend a digital thermometer for chemicals, as they need to be fast and accurate)
  • A grain focuser
  • Latex gloves
  • S breathing mask
  • Safety glasses
  • A hairdryer, as you need to evaluate your test strips when dry
  • Measuring cylinders
  • Black cardboard
  • Paper cutter

Optional items include:

  • Colour viewing filters
  • Bottles for your chemicals, if the ones of your black and white kit can be reused. They need to be of amber crystal or black plastic and have to be tightly sealed
  • Protectan or another solution to make your chemicals last longer once opened

If you already work with black and white printing, you’ll spend very little money. Your next step is to choose between these four development methods:

  • Open trays
  • A film tank
  • A paper drum (my recommended option if you can’t afford a colour processor)
  • A colour processor

If you opt for open trays or a film/paper tank option, you’ll also need to have these items together:

Open trays

  • Three tongs
  • One tray to make a tempered bath for your chemicals
  • Three trays big enough to fit your paper

Film tank/Paper drum

  • To make a tempered bath for your chemicals and your drum/tank

Storing and handling chemicals

You must follow the manufacturer’s instructions on correctly and safely storing your chemistry. I recommend using amber glass bottles, or plastic collapsible black bottles. You need to make sure that both the concentrates and solution bottles are tightly sealed. Also, you need to keep them protected from light and oxygen.

To accomplish that, squeeze all the air out of the bottles before closing them. If that’s not enough, you can use Protectan or an equivalent product. Protectan is a gas that is heavier than air, so it creates a barrier between your chemistry and air in the bottle, which prevents oxidisation. If you want a cheaper method, you can put marbles inside the bottles until there is no space for air.

Always keep all the chemicals in a cool, dry and dark place.

The manufacturer may say the chemicals won’t last more than “X” weeks/months, but that’s not always the case. When I did my first test strip, my lab provided chemicals that had been opened many years ago, so I tried them to see if they were still in good working condition. It turned out they were. So, before discarding your old chemicals, you can give them a try and you might save some money.

To test old chemicals, just mix them following the manufacturer’s instructions and run a test strip. If you can’t adjust the colour balance, or it’s too close to the max values of your enlarger (let’s say you had to use 120Y 120M on an enlarger with 130 as max value), then you probably should buy a new set.

Safety notes

The colour enlarging process has two very important aspects you have to be very cautious about: darkness and chemicals.

As I mentioned, there are some steps of the process that have to be conducted in complete darkness. This means you have to make sure you have no light leaks inside your darkroom. To make sure of that, turn the lights off, wait a couple of minutes, and if you can see anything, search for the light source and cover it. Duct tape is particularly useful to cover the doors. Operating in complete darkness means your darkroom needs to be very organized, so you know where everything is at any moment so you don’t stumble.

Colour chemicals are toxic if not handled safely. Now, this may alarm you, but you can take precautions to make this whole process totally safe. You must use latex gloves, a breathing mask and safety glasses when you work with any chemicals. Also, you need to make sure your darkroom is well ventilated.

The fundamentals of colour

Primary and complementary colours

There are three primary colours in negative colour photography: red, green and blue. Each film emulsion contains three layers of filters sensitive to those colours, and the same applies to colour paper. When those layers are combined they create the full picture.

As each film and batch of paper has different colour dominance, we must adjust the parameters of the print to get the colour balance that we want. How do we do that? By using the enlarger’s colour filters.

Red, green and blue are the primary colours of photography, but we also need to adjust their complementary colours. Those colours are magenta, yellow and cyan. Here’s an example of those primary and complementary colours:

Primary and Complementary Colours
Primary and Complementary Colours

You have to remember which are the primary and complementary colours, and how they work together, so this image is going to be your Bible. Keep in on your phone or print it off, because any doubt you have will be solved by looking at this image.


Our colour enlarger has filters for each complementary colour. When the three are combined, they create some kind of grayish colour, so we’ll try to not use all three of them unless it’s absolutely necessary. For example, we’ll try not to use the cyan channel unless we can’t use more magenta and yellow, as adding some cyan would create an unnecessary level of gray.

When you’re trying to set the filter for the first time, you have to check your paper box to see if the manufacturer has included any information about the starting point for filtering. It’s usually under the name of “white light data”. If there is no information, try 70Y 50M to begin with.

The first time I made a test print, I had a deep red dominant. DON’T PANIC. It’s perfectly normal that your filtering will deviate a lot from the one you should use the first time round, and you might have to make a few test prints until you get it right.

Durst M605 enlager head
Durst M605 enlager head

When filtering, look at the colour Venn early on this article. Let’s say you have a dominant magenta. Since you are working with negatives, you would add MORE magenta to block it. On the contrary, if you had a dominant green, you would subtract some magenta (it’s complementary colour) to correct it.

The same logic applies to all other colours. Be especially careful with dominant reds. Since you don’t want to use the cyan filter, when you need to add more cyan, you can subtract some yellow and magenta instead, until you can’t subtract more.

The amount of colour filtering you have to add or subtract depends on how strong the dominant colour is. If it’s really subtle, try to modify it by 5 or 10 units. If it’s very vivid, you can try higher values like 20 or 30, especially when you’re doing your first test strips to determine the starting point for your enlarger.

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Also, keep in mind that every time you change filtering, it affects the exposure. If you’re changing your filtering when you’re making test strips, do another, since the correct exposure may have changed. If you’ve made your first print and you need to change the filtering, check your enlarger’s filter factors, as it will help you calculate your new exposure time depending on your new filter values.

Every enlarger has its filter factors specified in its manual and if you’re doubtful of your filtering skills, there are tools like the Kodak Filter Viewing Kit that can help you check how the new filter will impact your print.

Let’s use a real-life example:

RA-4 Printing - Filtering 45Y 45M
RA-4 Printing – Filtering 45Y 45M

This was my first test print ever. The filtering was 45Y 45M. As you can see, the dominant is deep red, so I needed to add more magenta and yellow. I used what was supposed to be the white parts of the image as a reference to see the dominants.

RA-4 Printing - Filtering 75Y 65M
RA-4 Printing – Filtering 75Y 65M

The second test strip filtering was 75Y 65M. As you can see, it’s still very red.

RA-4 Printing - Filtering 85Y 85M
RA-4 Printing – Filtering 85Y 85M

The third test strips filtering was 85Y 85M. Now there’s a yellow dominance, but it seems more yellow than red, so I will only add 10 units of magenta for the next test strip, and a lot of yellow.

RA-4 Printing - Filtering 105Y 95M
RA-4 Printing – Filtering 105Y 95M

The fourth and last test strip was 105Y 95M. Now everything seems fine. Time to make the print.

And there you go. This was my first colour print ever. It doesn’t look really good when scanned with my cheap old scanner, but I assure you the colours on the print are 100% accurate compared to the real ones.

The RA-4 Process

The RA-4 process requires the following chemicals, one for each process:

  • Colour Developer
  • Stop Bath
  • Blix

You must follow the manufacturer’s instructions to prepare the chemicals. Usually, the kits do not include the stop bath, so you’ll have to buy some Acetic Acid and make a 1+49 dilution (so 2% Acid Acetic, 98% water) to serve as your stop bath.

When your chemicals are ready, you have to heat them in a tempered bath. They have to be between 30ºC/86ºF and 35ºC/95ºF. If you have a thermometer that can measure both in Celsius and Fahrenheit, I recommend to check it in Celsius, as it is easier to calculate the time needed for the development.

If you’re using a tank or drum, you should let it heat inside the tempered bath for a minute before starting the process. This will prevent temperature variations throughout the development.

Colour development

The first step is to pour the colour developer into the tank/drum and make it roll, or put the paper inside the tray that contains the developer and gently rock it. This step has to be done exactly for the following time, according to the temperature of your developer:

30ºC: 1 min 20 sec
31ºC: 1 min 13 sec
32ºC: 1 min 6 sec
33ºC: 59 sec
34ºC: 52 sec
35ºC: 45 sec

It is very important to pour the chemicals out of the tank/drum (or take the paper out of the tray) 15 seconds before the ending of this step because when the countdown comes to zero you have to pour the stop bath immediately. Also, if you’re using a tank, you can submerge the cap in water between this and the next step to reduce the possible contamination of the stop bath.

Stop bath
You have to pour the stop bath inside the tank/drum and make it rotate, or put the paper in the stop bath, for at least 30 seconds. This will stop the effect of the developer.

You have to pour the Blix inside the tank/drum and make it rotate, or put the paper in the Blix, for 1 minute.

At this point, you can switch the lights on if you’re using open trays. You can wash your print in running water in a tray or inside the drum/tank for 1 minute and 30 seconds. If you want to reduce the water waste with the drum/tank you can fill it with water and agitate for 30 seconds and repeat this process 2 more times.

You can let your prints dry by hanging them from a clothespin or using a hairdryer using the minimum heat. It’s very important to dry your test prints before evaluating the colour balance.

If you’re using a film tank you have to be very fast covering your tank and putting it in a horizontal position to start rolling. That’s because until that moment you’re only covering a fraction of your print with the developer, and since the steps are so quick, that can lead to uneven development.

Make sure the inside of the drum/tank is clean and dry, as water can produce changes in the dilution, and chemical residue can lead to chemical contamination. To prevent this, I always wash the print inside the drum, and I let it dry as I prepare myself to expose the next test strip or print.

Never discard the chemicals down the waste pipe, always find the recycling center of your community.

Making your first print

Durst M605 negative carrier
Durst M605 negative carrier

Now that you know the fundamentals of colour and filtering, it’s time for you to make your first colour print. Since we assume you already know how to make black and white prints, we will not cover the use of the enlarger (how to set the film in the carrier, focusing, etc).

Once everything is set and focused, set the aperture of your enlarger to f/11 and the timer of your enlarger to two seconds. This is the aperture and time I normally use, but it may vary depending on the paper batch and your enlarger, so feel free to change it according to your needs. Set the filtering to the one specified in your box of paper, or else you can try 70Y 50M.

In complete darkness, cut a strip of paper and place it under your mask. My suggestion is to place it where the main subject is, but also try to find a spot where you think you can find some neutral white, as it can help you determine the filtering. Give the paper the exposure set on the timer.

Now, with a piece of black cardboard covering the lowest part of the strip horizontally, expose again for the same time. Keep covering upwards and exposing until you have covered the whole strip. Now follow the RA-4 Process part of this guide with your test strip to develop the paper.

When the test strip is dried, evaluate the exposure and filtering, and adjust as needed. If you change the filtering, run another test strip. Repeat. When you find the right filtering and exposure time, make your final print. Expose the full paper for the correct time and filtering, and then process.

Once your print is dry, you may find that the filtering is a bit incorrect. Since you will normally need to perform subtle modifications, you don’t have to run another test strip. Instead, I suggest you to have a look at your enlarger’s filter factors. These are a series of factors that, given the first exposure time, the first filtering and the new filtering, will give you the new exposure time. Every enlarger has its own factors and formulas to calculate exposure times, so make sure to take a look at your enlarger’s manual.

Contact sheets

Besides everything we listed in the Kit List above, to make your first contact sheet you’ll need a contact printing frame. For colour, the best ones will be the ones that have strips to put your film strips, as it can be very difficult to position the strips in complete darkness.

You’ll also need:

  • A box of 24x30cm paper
  • A black cardboard

The first thing you’ll do is put your strips of film on the printing frame, with the emulsion side facing up. Then set the aperture of your enlarger lens to the smallest f-number and make sure the light covers the entire frame. Set the timer of your enlarger to one second. Set the filtering to the one specified in your box of paper, the one you used on a copy of the same type of film, or else you can try 70Y 50M.

Now, in complete darkness, cut your paper to cover just one strip of films, as it will save you a lot of paper. Put your strip of paper under the strip of film, emulsion facing up. Give the whole strip one second of exposure by turning on the timer. After that, cover half of the first photograph with the black cardboard and expose for one second again. Move the cardboard to half the next photograph and repeat until you have covered the whole strip. At this point, you’re ready to follow the RA-4 process part of this guide with your test strip.

RA-4 Printing - Contact strip (single)
RA-4 Printing – Contact strip (single)

When you’re done and the print is dry, evaluate the exposure and the colour filtering. If the different exposures go from too light to too dark too quickly, try closing the diaphragm of the enlarger one step (larger f-number). If there is a colour cast, correct it according to the Fundamentals of Colour part of this guide. Each correction will require you to do another test strip. Keep in mind that the correct exposure or filtering may vary from one photograph to another, depending on if they were overexposed, underexposed, shot at daylight or under tungsten light. Just try to have an average good exposure and filtering.

When you’ve come up with the correct filtering and exposure time, you’ll be able to expose the full contact sheet. Just place the whole paper under the strips of film, emulsion side facing up, give it the correct exposure time and filtering, and process. Congratulations, now you have your first colour contact sheet!

Tips for filtering

Use everything you have as a reference. Write down every filter you used for your prints or contact sheets, and use them to calculate a starting point for filtering.

For example: before I did my first contact sheet, I had two prints with the right filtering applied. One was from a Kodak Ektar 100 film, and the other from a Kodak Portra 400 film. I noticed I had to use 30% less magenta on the Portra one, compared to the Ektar one. So, when I got the right filtering for my Ektar contact sheet, I then tried to print an Ektar contact print. I just applied 30% less magenta to the filtering I used for the Ektar film and did the test strip. I ended up nailing the filtering on the first test print.

Let’s imagine it’s the opposite way, and you have two contact sheets from different films with the correct filtering. When you make a good copy, you can use the filter difference between the contact sheets to try a starting point for a copy of a film from the other type. Logic will save you a lot of time and paper.

Final thoughts

I hope this article has been useful for you, and that you take the step to try and make your first colour prints. You will find it’s not that hard, and you’ll soon be very passionate about it! I also hope that, if the number of people printing colour begins to grow again, maybe we’ll have more paper stocks on the market (maybe some Ilfochrome to print slides? Fingers crossed!).

If you want to dig deeper into colour printing, I recommend you to read The Darkroom Handbook by Michael Langford, and Post Exposure by Ctein.

Thanks for reading,

~ Abel

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About the author

Avatar - Abel Rico

Abel Rico

I’m Abel Rico and I’m a film photographer based in Barcelona, Spain. Still studying photography and continuously learning new techniques. I’m specialised in portraits and landscapes. I shoot mainly on 135 and 120 film. My most precious moment of the...


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  1. Very good article, however there is really good option option for print processing which you haven’t mentioned. The Nova print processing tank is a thermostatically controlled unit with separate slots for each chemical. I’ve been using one of these for two years; the print is simply dunked into each slot in turn, around 2 minutes in total. The chemicals stay viable for many weeks with a small amount of replenishment after each printing session, so the only preparation before use is to switch it on a couple of hours in advance.

  2. Ilfochrome was terribly toxic and led to birth defects, it’s not something you should hope comes back unless it’s with non toxic chemicals

  3. Thank you very much for your article. I am getting closer and closer to colour printing. As just a b&w practitioner I have few questions. 1) How do you compare your prints to those from wet process form the lab? 2) What darkroom timer do you use that tells you in complete darkness that it is time stop developing?
    I will probably have more questions when I start but for now I will mention about Nova processors that can be used in RA4 printing. This is what I am going to use.
    I am very curious how those prints look like in reality.

    1. Thank you for your feedback!

      1) Your wet prints from your lab normally are completely automatized, so you don’t have much control over the final look. When doing it yourself, you can dodge, burn, change the colour dominance, etc.

      2) In my lab we have a GraLab 300 timer. It glows in the dark, and you have to keep it very far from the paper. However, it still forces you to work in complete darkness for a really long time. If I were you, I would rather invest on a paper drum, as you can work with the lights on once you put the paper inside and it’s securely closed.

    1. This lamp, as like other safe lamps for colour, is meant to be used only for a brief moment if the situation demands it. Any colour paper should be exposed to any safe light for more than 30 seconds/1 minute. So therefore, you have to work in complete darkness, or you might fog the paper and possibly alter the colour balance.

  4. Love this article! Love RA4! But there should be an option 5, which is the way as far as I knew most people did it, with a ra4 machine. Doing it other ways is great, although more difficult, but not mentioning it is weird 😉 They don’t make ‘m anymore (yet) but with some patience you can find one.

    And please store your chems in wine bags, it stays good for months instead of days.. )

    1. Thank you for your feedback! When you say RA-4 machine you mean a paper processor or a minilab? I didn’t include a paper processor because the process is entirely automatized, as I also didn’t include the minilab because the machine does everything for you and there is no “darkroom” involved. However, when using a paper processor you still have to run test strips and calibrate the colour balance, so therefore I think you’re right. I will write a brief text about the paper processor and ask for it to be included in the article.