26. August 2003
Updated 21. Oktober 2005 - Curves created by users of GB
Updated 19. January 2005 - Now with support for Adobe® Photoshop®!
Updated 18. May 2004

Printing
Black & White Photos #2
- Balancing the grays

"Printing black & white photos on a color inkjet printer can be tricky. Avoiding color casts is very difficult and often it can't be totally avoided."
This was how I started my last article on printing black & white images on inkjet printers. My approach to the color cast problem then was to use the black ink only.
However, for a smoother tonality and for fine grained films, it is preferable to print black & white images using all colors of the photo printer.

Using all colors to print Black & White?
How is it possible to print black & white photos using all colors of the printer?
Well, if you start with taking a good look at your monitor right now (use a loupe) which emits light, you will see that the gray areas of the screen is made by emitting equal amounts of Red, Green and Blue light. The stronger the colors get the lighter the gray level.
On print it works in a similar way, although light is not emitted, but rather reflected from a paper, the principle is still to combine colors to create what looks like gray to our eyes.
Take a look at one of your color magazines and find a black & white picture. Use the loupe again and watch the CMYK (Cyan, Magenta, Yellow and (K) Black) screen patterns:



Move a bit away and you will see that the picture above is actually a black & white photo - well, more or less, you might see a color cast on your screen.

A photo printer works in a similar manor, however without the screen pattern. The printer driver is responsible for converting the gray levels it gets into a colored pattern. Since a photo printer often uses something called "Error Diffusion" or perhaps even "Stochastic screening" the dots aren't put down in a screen pattern, but rather in almost random order, to form something that looks like continuos tones.

Sounds good, what's the problem?
Well, for many of the photo inkjet users, the problem is straight forward: The black & white prints does not show neutral grays. A color cast is often seen in some of the gray levels.
This problem isn't limited to inkjet outputs - take a critical look at the black & white photos from your color magazine and you'll probably see a greenish or magenta color cast there as well.
Often the "amount" of color cast you see, depends on what light you see the print in. This phenomena might be related to what is known as "metamerism" - the effect that a print shows different colors in different lighting situations. The color cast in black & white photos might be more visible in some situations than in others.

Can the problem be solved?
The problem with color cast can indeed be reduced and in some cases as good as removed.
This article and the accompanying software will help you.
There are a number of very good articles online which inspired me to the approach described in this article and you should read them also when time permits - you'll find the links below.




What is needed?
Before you read on, I will stress that the process of removing the color cast from your black & white prints can prove to be time-consuming and a bit frustrating. However, if you follow the guidelines here, it shouldn't be impossible to get good results with a few hours of work.

Software
You need to download the accompanying software - the PHOTOgraphiacl.NET Gray Balancer or just GB - as I call it.


Download PHOTOgraphical.NET Gray Balancer Now!

You will be prompted to give your e-mail address in return for the software (if you are not already a newsletter subscriber).
You also need the Picture Window Pro software. If you aren't using that already, you really should give it a try. You can download a 30 day trial here.
If you still prefer to do your normal image manipulation in another software solution, then there is no problem with that. You then just need to use the Picture Window Pro for the final printout. I find the Picture Window Pro software to be very good and usable for photographers, but it is possible to just use it for the very final state in the following examples.
It would also be very preferable that you have a good paper/printer and profile combination that you know works well for you color pictures or perhaps you have a setup that already produces nearly neutral gray pictures.
The less color cast you start out with, the easier it is to get a perfect result (well, of course you might say...). Having said that, even a quite severe color cast can be removed if you are patient enough.

IMPORTANT!
[Update 19.01.05] Now GB also supports Adobe® Photoshop®!.

With the newest version of the Gray Balancer described here, you can choose to use a Kodak Gray Scale Card to aid you in balancing the neutrality of your prints.

Picture Window Pro
Picture Window and Picture Window Pro from Digital Light & Color has a nice little feature called Tint. Select Transformation/Gray/Tint from the menu:



The Tint feature can color certain areas of a gray scale picture. You can use the Tint control to color certain levels of gray in a picture to a certain color.
But a color tint was exactly what we are trying to avoid right? Well, yes, BUT if we can slightly tint the levels of gray that has a color cast with the OPPOSITE color (the complementary color), then we can reduce the effect of the color cast.
So, if your print shows a, say green color cast in the highlights then we need to tint the highlight with the opposite of green. This will result in a color picture that will show a color cast on screen, but it will be a color picture that will print neutral on the paper and printer combination we are working on.
I will not go deeper into the how the Tint function in Picture Window is used, because the Gray Balancer software will automatically produce the Tint file that we need and which can be loaded into the Tint dialog. Read on.

The Gray Balancer
The Gray Balancer software will help you to identify and modify the levels of gray that shows a color cast and it will create a Tint file that can be imported into the Tint feature in the Picture Window software.
You will then simply apply that tint file to your gray scale image and print(!)

Step by Step
So, here is what you should do:
Download and install the Gray Balancer (GB) software.
If you have the previous version of GB installed, the new version will simply overwrite the old one. Should you experience any problems then please uninstall the former version and install the new version again.
The GB should run on all Windows platforms (95, 98, ME, 2000, XP).

When starting the GB you'll see this window:



On this first page you will be creating the gray scale for later printout with your ink and paper combination.
You can create a grayscale in two basic ways: Create the steps in percentages of black or as densities.



(The first version of GB only gave you the option of saving a gray scale card using percentage steps - pressing the "default" button, will therefore create such a grayscale).



Another option is to use densities rather than percentages (see picture above). Here you must choose the start and end density as well as the gamma slope. Pressing the "Kodak Q-13" button will create a grayscale that matches the densities of a standard Kodak grayscale card. But other cards are available and you can make your own settings if you prefer. You can also choose to add an all black bar.

In both modes you can choose how many steps you want to see and if you want to add the picture or not.

When you have the gray scale you want, then you can save it as a picture file.
The grayscale created here is actually a color picture. When we later apply tint to the picture it will be converted to color anyway (had it been a grayscale picture).
Load this picture into Picture Window and print it out from there.
It is important that you choose a "good starting point" when printing the black & white pictures. By this I mean that you should use a setting (printer setting) that you know will produce a decent picture. It might be that you have a certain paper and profile combination that already produces good (but not perfect) black & white pictures. By doing so, you have a better chance of an excellent result.
For this example I'm going to "gray balance" Epson Premium Glossy Photo Paper and I'm simply going to print it out using the Epson profile for this paper. You can use ANY setting you like, as long as you keep that setting throughout the entire process here AND that you use that exact same setting when printing the final black & white photos.
I'm using the default gray scale in this example, but I'll show examples of using the Kodak Gray Scale as and aid later - the two processes are nearly the same.

Here is what I got when printing the grayscale on Premium Glossy Photo Paper using my Epson 1290 :



The lighter grays are very neutral, but from 50% and up to 80% we see a color cast (it might be difficult to see on your screen, but it is more apparent in the real print than here). At 50% and 60% the cast seems very slightly magenta, but from 70% to 80% the cast is clearly green. The green cast is the most objectionable when printing my black & white pictures and it really makes the photos useless. So let's move one and try to remove this ugly cast.
It is important to note, that you must let the print dry for at least half and hour before evaluation. However, if the paper is not glossy it might dry more quickly.

Now go to Step 2 in the GB. This shows a page to the left containing a number of colored patches. This requires and explanation:
We want to print out a number of ALMOST gray patches to identify the patch that looks the most neutral gray in the light that the print is to be shown in. We can produce patches for each of the "problem levels".
If you enlarge the window of the GB you will see that the colors of the patches changes more or less "rapidly". By typing values into the boxes on the right you can select what gray levels (in percent of black) you want to print and the step between each patch.
Try out different values and see what it looks like. You can press the Save button to save the resulting picture.
In my example there was problems with 50 to 80 percent, so I choose 50, 60, 70, and 80% and I choose a slightly larger stepping for the dark tones than for the lighter ones. It seems that it is more difficult to distinguish between the patches at the darker levels than in the lighter levels. So my setting is like this:

IMPORTANT: When using a density based gray scale, the percentage of black is also printed at the bottom of each bar, in this way you'll know what black level to type in.

I save this picture and load it into Picture Window and print it using the EXACT same settings as I used when printing the gray scale - I use the Epson profile for the Premium Glossy paper when printing, but you can use any printer setting you like.



Let the print dry again and then start evaluating the colored patches. Try to identify the ones that looks most neutrally gray for each of the levels.
It can be quite difficult, I admit, to find the truly neutral gray patches. Sometimes it will help if you have something with true neutral gray colors - it could be a Kodak Gray Scale card or maybe just an old black & white print to sort of "calibrate" your eyes.
Yes, I know that this sounds a bit "unscientific" and not very serious, but believe me, the most important thing is, that the colors look neutral OR has a color cast that YOU prefer in the light that you want the picture to be presented in.
The patch in the middle (with three identical numbers) are the unchanged one - the one that is currently "supposed" to look gray, but might not do (this is why we saw a color cast in the first place).

In my example test here, I've chosen to let the 50% patch be and just focus on the 60, 70 and 80% to begin with. Remember that you are not just affecting ONE single color when adjusting one of the gray levels. When you change one level, say the 60% black level, you are also affecting the surrounding levels slightly, so make small adjustments to start with.
Now, that we have selected the patches to be adjusted, we move on to step 3 in the GB.



(You will notice that the GB program let you type up to 8 sets of numbers in)
Now type in the three small numbers from each patch you've selected. The order does not matter, just type in in the order you like.
It's about time now, that we take a deeper look at the numbers we are typing in. You might already have guessed that they aren't just magic numbers, but in fact Red, Green and Blue vales. The green is kept at the same level throughout the patches. This is done because the green color is closely related to the luminosity. However, by changing the blue and red amount, we can alter the way the gray color looks - which of course can be seen very clearly on the colored patches that we printed out earlier.


Example of patches from 60%

Now save the final Tint file by pressing the Save button and go back to Picture Window.
In picture Window we are now going to Tint the gray scale that we printed earlier and see if it has an effect.
Focus the Gray Scale and select Transformation/Gray/Tint from the menu:



Press the Opt button and load the Tint file and press OK.
A new picture will be created which is slightly adjusted in the colors.
Print the grayscale with the same settings as before and evaluate this new print.
If it needs more adjustments, then simply find some even better matching patches and go to step 3 and retype the new numbers, save a new tint file to be used and so on.

Moving to the right in the colored patches will increase the amount of blue, while moving down will increase the amount of red:



After a while you might not even have to go back and look at the patches, but you can change the numbers you type in yourself.
Example:
You have found this patch to look a bit too red : 208.204.208
and therefore you simple reduce the amount of red a bit: 206.204.208

Summarize
The entire procedure once again:
1. Download, install and run the Gray Balancer (GB) software.
2. Use Step 1 in GB to save a Gray Scale card.
3. Print the Gray Scale from within Picture Window Pro in whatever setting suites you the best.
4. Identify the "problem levels" and go to Step 2 in GB and make patches for those levels. Save the final "patchwork" image.
5. Print the colored patches with the same settings as in 3 (above).
6. Find the patches that looks the most neutrally gray and type the values into the boxes in GB in Step 3. Save the resulting Tint file.
7. Use the Tint feature in Picture Window to adjust the colors of the Gray Scale, by loading the tint file created in 6 (above) and print using the same settings as in 3 (above).
8. Evaluate the new grayscale printout. If not quite neutral yet, go to 6 (above) else go to 9 (below).
9. Load a grayscale image into Picture Window Pro. Add the tint file just created and print using the same settings as in 3 (above).

The result
After four "sessions" of slightly changing the levels for 60, 70 and 80% (I didn't really need to change the 50% level) I was satisfied.

Original:



Final:



As it can be seen from the picture above my gray scale now looks a lot more neutral (again it might be difficult to actually see all the subtle differences that are present in the real print), it might not be perfect, but I think this will do to make what looks like a neutral black & white photo - let's try it out.

A test print
I found a picture from my old wet darkroom days.
It was taken on Ilford FP4 and printed on Ilford paper of some kind (I don't recall which), however I do remember that I used a Rolleicord with a 75mm Tessar and that the enlarger had a Nikon lens. I'm certainly not going to brag about my wet darkroom skills, but this picture might be good for a little comparison.


Photograph of prints : Digital print to the left and analogue to the right

The contrast in the two picture are not identical, but the new digital print looks very neutral although with a somewhat more cool tone. It has just as many details as the "real" black & white print and all in all I'm now confident that I can make good black & white print using this technique.

Using a Kodak Gray Scale Card
In Step 1 you can choose to create a gray scale that matches the Kodak Gray Scale Card (Q-13).
You can buy the Kodak Gray Scale Card at Amazon.com for approx. $17.
This is a great help when identifying the most neutral gray patches.



If you print the gray scale about 8-inches wide, it'll match the size of the Q-13 Gray Scale.
You can then identify the problematic gray levels by placing the Q-13 card above the printed gray scale:



The red ring above shows you how to find the relation between the density and the black level (here it's density 0.40 corresponding to 34% black).
When the problematic levels are identified (marked with arrows above), I print the patch-card (as shown above) and I then find the most neutral gray patch by placing the Kodak Gray Scale on top:



In the example above I'm trying to match level 4 (density 0.4 = 34% black).

As it can be seen, the procedure when using the Kodak Gray Scale is exactly the same as the former procedure described above, only you have the neutral patches of the Kodak Card to aid you in deciding what patch is most neutrally gray.

Tips & Tricks
It can be of great visual help to cover the other gray patches when trying to find the most neutral one:



Also remember that the temperature of the light you are evaluating in has great influence on how you see the gray patches. Try to make the tint file in approximately the same light condition as the final photo is to be presented in. Mix daylight from a window with light from a normal light bulb for example.

Metamerism
The big joker - in my opinion - when dealing with monochrome prints is metamerism.
metamerism is the phenomena that a color cast will change in different light situations. If you have made your tint file in normal daylight, you'll often get a nasty color cast when looking at the same print in tungsten (artificial) light.


The example above shows the same two pictures in normal daylight (to the left) and tungsten light (to the right).
The upper print is an inkjet print while the lower is a traditional monochrome print. The white balance might not be totally identical here (the upper white border of the papers should be perfectly white in both examples), but still notice how the traditional print hardly changes in color while there is a severe color cast in the inkjet print shown in tungsten light.
How bad this phenomena is, depends on what printer, ink and paper combination you are using.

Trying to deal with metamerism
Getting rid of metamerism is almost impossible. The best way is to find a paper that doesn't show this huge change in color cast.
But, you can also use the Gray Balancer to help you with the worst problems.
If you select the Step 4 tab in GB you'll see this card:



This picture can be saved as a file and it contains 256 levels of gray.
Print it out using the tint file (it's very important that you print these patches, using the same settings as you would when printing a photo, including using the tint color cast file created above) and look at it in different lighting situations. You'll then notice that some of the patches are more prone to metamerism than others.



It might be difficult to see above, but some of the patches are getting very brown in the tungsten light. I've marked these with a red ring. It can be several areas of patches that shows this very severe metamerism.
Now, the idea is to simply NOT print these difficult levels of gray. So, therefore we'll make a tint file that simply removes these levels from the picture(!)
But, this will cut away information in the final photo, you might argue. Yes, it is a compromise, but in some cases minimizing the metamerism is preferable to loosing a bit of image information.
Here is what you do:
Type in the start and end patch that shows the worst metamerism using Step 5 in GB:



As an example I have typed in patches ranging from 097 to 081 and patches from 056 to 048. You can type the numbers in in any order you like.
Then save this tint file for later use, by pressing the "Save As" button.

Using the "metamerism" tint file
Here is the procedure for using the metamerism tint file:

1. Load your gray scale photo.
2. Open the tint feature in Picture Window Pro and load the metamerism tint file. This will remove all the "unwanted" levels of gray.
3. Open the tint feature in Picture Window Pro and load the color cast tint file created in the first steps.
4. Print the picture.

A test print
Showing the subtle changes in metamerism using the procedure above is hard to do on screen, but I'll give it a try:



The lower photo was applied the metamerism tint file, and I hope that it can be seen, that the color cast is less severe that on the upper photo, which only had the color cast tint file applied.

Final note
A final note here will be that the glossy papers seems more prone to metamerism - they look very different in different light - and therefore my prints often does show some magenta cast in artificial (warm) light. A less glossy paper might prove to be better all in all for black & white prints.
I urge you to try it out for yourself and I'll be very happy to hear about your experiences, your results and any kind of problems you might have with the GB program - just mail me.

Support for Adobe® Photoshop®
The very latest version of Gray Balancer (from version 0.93) will now support the creation of Adobe Photoshop files instead of only Picture Window tint files.
You will now have the option to save your color corrections as Photoshop curves files and you can save your metamerism files as so-called Photoshop Arbitrary Maps - both files are loaded via the Curves dialog in Photoshop:

Saving the curves file from Gray Balancer:



Loading the curves file in Photoshop:



Your gray scale image must be converted to a color picture with three color channels prior to adding the curve file (this is done automatically in Picture Window when you add a tint file). Otherwise the procedure is the same as in Picture Window (described above).

New features in GB summarized
Here is a list of new features in the latest GB:
- Support for creating Photoshop curves.
- User adjustable gray scale, including density scale and percentage scale.
- Buttons added for creating a GB default scale and a standard Kodak Q-13 scale.
- Two additional steps added for dealing with metamerism.
- Re-load of previously created tint files.
- New main menu for easy operation.

Links
I did not myself come up with all the approaches described above. This article is strongly inspired by other very great articles, which I think you should take a look at when time permits.

• Norman Koren : Black & white, matting and framing. Highly Recommended Site!
• David Conn Calibrating Ink Jet Printers for Monochrome Printing

• Printing Black & White #1 My first article about printing Black & White photos using the black ink only.

Getting a Kodak Q-13 Gray Scale Card:
• Amazon.com Kodak Q-13 Gray Scale

Other (cheap) approaches to printing monochrome:
• Quad Tone RIP
A very interesting RIP based on the Gimp Print engine (mainly used on Linux). It has support for several Epson printers, using MIS inks or UltraChrome inks. I haven't tested it myself, but I've seen prints coming from the Epson 2200 with UltraChrome inks and they looked very neutral. The RIP software comes with ICC profiles for grayscale imaging.

Curves from users of GB
Users of the GB are sending me curves for different printer, paper and ink combinations.
You can download these curves from below:

Epson 2200
- by William McGloin

Download the curve

Paper:
Epson Premium SemiGloss

Photoshop settings:
Document profile is "Adobe RGB 1998"
Printer profile is "SP2200 Prem.Semigloss 2880.icc"
Rendering intent is "perceptual" w/ NO black point compensation

Printer settings:
ICM/no color adjustment
high speed OFF
edge smoothing OFF