Duotone cyanotypes #3 – Make negatives using GIMP

Part 3 in Matthew Bary’s series Duotone cyanotype is a detailed guide for creating cyanotype negatives using Gimp software. It covers steps for flipping images, adjusting colors, adding registration marks, separating images into color components, applying curves, and exporting negatives for cyanotype printing.

Writer and photography / Matthew Bary

Lets start with a picture we want to use based on the previous step Duotone cyanotypes #2 – Pick your subject. At this point, you should have either a digital image or a scan of an analog one on your computer, and use the highest quality and size you possibly can to retain as much detail as possible.

You will now need to download software to manipulate the image for the negative, I use Gimp which is a free download and will work on Windows, Apple and Linux systems.  Although this could be done in Adobe, I do not own a copy and have issues with the monthly/micro pay system so many companies now use. Anyone who reads this could figure out how to use it in the same way as I do. My goal is to make this available to as many people as possible and a free software option will allow more people to try it out.

Open the file

After downloading Gimp install it and open it up, Now go to file and open.

open gimp

File open

Then navigate to the picture you want, And click open.

Find image

You are now ready to make your negatives.

Ready to make negaatives

Flip the image to make a cyanotype negative the right way around

So first let’s flip the image so that when you print the negative it will be the correct way on the paper, to do this click on the image, transform, and flip horizontally.



And now the image is flipped.



Increase saturation for 2- or 3-layer cyanotypes

The next step is to manipulate the image to print correctly with the Cyanotype process and with this specific process as well. The first correction that has to be made is the saturation, due to the dull nature of this process you have to boost the color to get as much as possible out of it. This only has to be done for 2-color or 3-color Cyanotypes and not single-layer ones such as plain blue or toned.
Navigate to colors, then click on Hue-Saturation.
hue saturation
Bring the saturation all the way up and click ok, You can see in this split image just how much the color has changed.
saturation all way up
saturated image 

Add registration marks

The next step is a relatively easy way to put registration marks on the negative, while this is not completely necessary it will enable you to make the best image possible by registering the two layers as close as possible otherwise the image will be very blurry and mushy looking. I want to point out that this is not necessarily the best way to add registration marks – it is just a simple way to do it in this program. Go to filters, then Decor, then click add border.
filter decor add border
The border x and y size will depend on the size of your image, it just needs to be big enough to be visible and to contain the registration marks.
Add border
Now we need to make sure the color of the border is white, First make sure the delta value is set to 1 then click on the box labelled border color, although it looks complicated just drag the cross inside the large box up and left which will make the current color white, then click ok and finally click ok on the add border box.
Border colour cross Border colour white
Your image will now have a white border.
image with white border
Now we can add the registration marks to the border. There are two ways to do this, the first is to add four dots in the corners or you can add an actual registration mark in the corners. I will go over how to do both. The first method is simple. Simply select the brush function, adjust the size of the brush to make a large enough black circle to define between it and the border, adjust hardness to 100%, then click on the corners to add a circle in all four of them.
dot marks
The second method is more complicated but is a slightly better / more accurate method to use. First, you need to find a proper registration mark on the internet, you can find these by searching for registration mark PNG, it needs to be a PNG file as it has a transparent background. There are all kinds from a simple cross to dots with crosses etc, this is to make it easier to align the layers.
Keep the picture with the border added open (don’t close it!). Navigate to file, then open, and find the registration image you downloaded, then click open.
File open
Open registration mark
Open registration mark
Now click on edit, then copy.
Now navigate back to the image with the border.
navigate back
Now click edit, and paste.
edit paste
The registration mark will appear but will not be the right size.
Navigate to the layer with the registration mark, right-click on the layer then click on scale layer.
Scale layer
Adjust the width to the appropriate size to fit within the border. For the image in the example it was 35 but it will be different depending on your image size. If it is not right, just undo and try again. As long as the with and height are linked you only have to change one and the other will auto calculate.
resize registration mark
Now the registration mark will be resized but will have to be moved.
move registration mark
Be sure the move tool is selected.
move the mark  
Then click on the resized registration mark and drag it into a corner.
move tool
The final step is to click on the anchor floating layer button.
gimp anchor layer
This will make the change permanent. Now repeat those steps with the remaining three corners and you are now done with the registration marks.
Registration marks done for cyanotype negatives

Separating the colours

Now we need to separate the image into its individual color components. Navigate to colors, components, decompose.
Make sure RGB is selected and decompose to layers is selected then click on ok.
colour separation for cyanotype negatives colour separation for duotone cyanotype negatives colour separation for 3-layered cyanotype negatives
A new image will be made that is a gray-scale separation of all three colors red, green, blue.
One thing to note is what each layer is for.
Red layer = Cyan layer
Green layer = Magenta layer
Blue layer = Yellow layer

Making adjustments and curves

The final steps are to make adjustments on the red layer, invert it to a negative then export it as the cyan negative.
And finally we adjust and combine the green and blue layer then invert them and export as our magenta negative.
Now a note on “curves”.
There is not a lot of easy-to-understand information on curves so I will try to demystify and make it simpler to understand. So let’s say you start with a picture like this:
grey scale image
If you simply invert it and print it you get a negative that looks like this.
invert the image to a negative
But when you print your Cyanotype it looks like this.
bad negative cyanotype
As you can see you lost a lot of the shades from the original image, this is due to the nature of the sensitivity of the Cyanotype chemistry. It is not linear in nature but curved relatively to the original print. This curve is different depending on which type of alternative photography printing process you use. Essentially you must lighten certain tones and darken others for it to print more linearly. Here is a negative that has been “flattened” or a “curve” applied.
flattened negative with a curve
As you can see it looks much different from the negative that was just inverted but this is how the cyanotype print looks from this negative:
Good negative for cyanotype
This is the step which is the hardest to get right and I spent almost a year trying different programs and techniques,  which mostly failed. The curve changes based on the paper you use, the transparency film used to print the negative on, the printer and ink used to print the negative, and the chemistry of the process you are using. As you can see it presents near-infinite variables but don’t let that scare you off. I believe I simplified the process greatly, at least for this method.
There are several resources for making curves that are much more detailed and professional and I encourage anyone to look into them and try them out, but the method I use I find sufficient for the duotone cyanotype process.
What I am doing is to basically lighten the positive image and then invert it which does a good job for flattening the curve. The only downside to this method is that it takes a little longer to print as the negative is much darker. You see the programs that are designed to make curves do it in such a way that as much light as possible is transmitted through the negative while retaining the detail and tones. I have nothing against this, but I have found my personal experience to be that the slower the cyanotype prints, the better detail and control I have with it. For those who have been using the curve programs who do not think this can be done simply: I have tried every method I could and even had other people help make curves and none of them worked as well as this simple method, I always got better tones with my method than any curve I tried. 
With the separated image open, click on the eye icon on the green and blue layer to close them, and leave the red layer on. Make sure the red layer is highlighted so only this layer will be visible and changed.
Negative curves
Now click on colors then brightness-contrast.
Brighness control negativ
Adjust brightness all the way up and click ok.
Brighness negative
Now click on colors, then exposure
Exposure on negative
Adjust the black level all the way up and click ok.
invert colours
Go to colors then click on invert.
Negative image
You will now have a negative image
The negative image
To save, click on file then export as, name the layer “Cyan” and make sure .jpeg is at the end. 
save image
Make sure you navigate to where you want the image saved then click export.
Make sure the quality is set to 100% and click export. This will save the cyan layer as a separate image.
cyanotype curve
The cyan negative is now saved and ready to print.

Making the magenta layer

Now we have to make the magenta negative. I tested several combinations and the best one for this method of due tone is to adjust and combine both the magenta and yellow layers then make a single negative, this retains the most detail and color in my opinion. If you were going to try a three layer Cyanotype you would just adjust invert and export all three files individually. 
Make sure the green layer is the only one selected and highlighted.
Then go to colors and adjust brightness and contrast
Bring the brightness all the way up and click ok.
brigtness negative
Next click on colors then invert.
invert colours
Select blue layer
Now make sure only the blue layer is selected and highlighted.
Select the blue layer
Again go to colors then click on brightness and contrast. Bring the brightness all the way up and click ok.
cyanotype negative
invert the image
Finally, click on colors then click on invert.
print a cyanotype negative duotone negatives
Now that both layers are adjusted and inverted we just need to combine them and export them to print. First Make sure both the green and blue layers are selected and that the green layer is highlighted.
Select green and blue layer
Next on the green layer change the mode from normal to addition.
change the mode
The green and blue layers are now combined.
layers combined
Now go to file then export as. Name the file “Magenta plus yellow” be sure there is a .jpeg at the end and be sure to have the folder where you want it to go selected.
save the magenta and yellow layer save the magenta and yellow layer
Make sure the quality is set to 100% then click export.
export the negative
You now have your two negatives for the due tone process.

Two negatives for the duotone process

The complete series


Matthew Bary is a self-taught photographer (spending more time on printmaking than actual photography). He got into alternative photography five years ago and is amazed at all of the processes and innovations done with very old techniques. Matthew Bary lives in Corydon, Indiana, USA and often photographs his local surroundings.

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