Help with Illustrator blending modes

[Jason Burnett]

I spent a good hour or two writing out a detailed post about some confusion I have witessed regarding blending modes in Illustrator. I included a diagram that demonstrated the blend modes  did not care which definition you used to create your color, the results would be the same.. 

When I tried to submit the post, I got an authentication error and I just don't have it in me to write it all out again. Here is a JPG of my diagram demonstrating the same results for different blend modes in eery color space in Illustrator. 

I am hping that I did something wrong and that someone can figure it out. DM me for the original Illustrator file where you can select any circle on the page and view its color definition and blend mode.

[Jacob Bugge]

Jason,

Can you state which blending modes are involved and roughly how in the confusion you have witnessed?

Based on similar posting error experience I try to remember to copy (the HTML/Source code of) important/long posts in a text editor before hitting the Post button, and sometimes I write the full post in the text editor and copy it to the Reply box..

[Monika Gause]

Which color mode is the document?

The color mode you set up in the color panel does not matter. The color will always be in the document color mode.

[Jason Burnett]

I think you are mistaken here.

To test this, I create a new document in CMYK Document Color Mode. I draw a rectangle and fill it with an RGB color that is outside of the CMYK gamut. According to your logic, that should not be possible because the color will always be within the limited gamut of CMYK.

There would be no need for Gamut warnings in CMYK mode if Adobe limited your available colors to the CMYK gamut.

[Doug A Roberts]

I create a new document in CMYK Document Color Mode. I draw a rectangle and fill it with an RGB color that is outside of the CMYK gamut. According to your logic, that should not be possible because the color will always be within the limited gamut of CMYK.

By @Jason Burnett

It is not possible. The RGB values are out of gamut, but the colour you created on the artboard isn't.

[Jason Burnett]

Adobe's primary goal is to achieve the best possible color fidelity. Your color data is stored in your document the way you enter it (whether that be out of gamut or not). The reason for this is they are trying to preserve as much color data as possible. The preview you will see is limited to the CMYK gamut (because that is a subset of RGB, it's easy to do) but the RGB data is still present. When you flatten artwork, export, or print the document, you get to pick a medium. That medium applies the REAL rgb - CMYK color profiles for the intended output method and clips your out pf gamut colors ONLY as you print or export.

There is no accepted universal CMYK color model. The only valid color spaces that use a CMYK model are those which have a real world component like a pigment or ink and a press. It is only when there are measurable output values for CMYK that it makes sense to apply a CMYK profile. This is why the Adobe Color site stopped allowing people to pick the CMYK color to generate colors. It became clear that CMYK is entirely dependent on output media and method. The only CMYK models that existed were necessarily tethered to output media and devices in CMYK Print Color Spaces or Export Color Spaces. Not for working files.

So working in CMYK document color mode only limits your perceptual enviroment (how things look on the screen), it doesn't clip colors and it doesn't change how your colors are stored. Your color picker will flatten your colors and give you CMYK because of the document mode. That's what the color picker does--it gives you the perceptual value of the color you are picking. In CMYK Mode it will give you CMYK. But your color stored in the element itself, if selected and viewed int he Color Pallet still contains the RGB definition and still has the gamut warning lett you know it cannot be directly converted to CMYK.

RGB Values are never out of RGB gamut. The monitor can produce any combination of RGB without a problem. However, when one says the RGB Values are out of gamut, that means that CMYK printing cannot reproduce those colors. The color is still in RGB until you print, export, or flatten (which is what the color picker does) . Even when it shows you values in CMYK< the actual color stored is in RGB or whatever model you used to generate the color. Even if it is out of gamut for CMYK.

[Doug A Roberts]

Adobe's primary goal is to achieve the best possible color fidelity. Your color data is stored in your document the way you enter it (whether that be out of gamut or not). The reason for this is they are trying to preserve as much color data as possible. The preview you will see is limited to the CMYK gamut (because that is a subset of RGB, it's easy to do) but the RGB data is still present.

By @Jason Burnett

I don't think this is true. If you try your test above (create out of gamut RGB colour in CMYK doc, save and close, reopen file), you get an in-gamut equivalent in the colour panel. If you create an out of gamut object, select an in-gamut object, then select your out-of-gamut object again, the colour panel shows an in-gamut colour again. Where is it evident that the RGB data is stored?

[Ton Frederiks]

"RGB Values are never out of RGB gamut. The monitor can produce any combination of RGB without a problem"

I am not sure where you've got this knowledge, because it is not true. Most monitors can display sRGB (that's why it was invented as the lowest common determinator), but many can't get beyond that. In this CIE xyY diagram you will see 3 different kinds of RGB, sRGB, Adobe RGB and Wide Gamut RGB.

It is clear that many of the Adobe RGB and Wide Gamut RGB colors are out of gamut for the sRGB color space.

[Jason Burnett]

We weren't talking about the wide gamut or pro gamut RGB. Those spaces, though RGB, are not available to set your document mode to. You aren't getting PRORGB or higher gamut RGB than your monitor can display when you set your document color mode to RGB.

Just like there are numerous cases where the printable CMYK color range depending on substrate can produce colors that are out of gamut for RGB, we aren't talking about using flourescent inks or metallic substrates when we set out document color space to CMYK. You won't find CMYK Colors, to my knowledge, in the Document Color Space that cannot be produced by your monitor in RGB.

They even make CYOBM Pigment based dispalys that add special pigments to the dispay that dispay ultra-high gamut RGB that CIE is still charting. I was just reading about them on the Chromacolor site. But that's all outside of the scope of this disucssion which uses the lowest possible denominator to APPROXIMATE color replication when printing or on the web. Not fort high end video or other media.

[Ton Frederiks]

??? We weren't talking about the wide gamut or pro gamut RGB. Those spaces, though RGB, are not available to set your document mode to ???

[Ton Frederiks]

Whatever you select in the Color panel, Grayscale, RGB, HSB, CMYK, Web Safe RGB, it is just a way to select a color.

That color will be automatically converted to the Document color mode, RGB or CMYK. The exception is a spot color which can have a Lab color definition independend of the document color mode.

[Jason Burnett]

Create a new document in CMYK mode.
Draw w square and fill it with #0065D7

Thius color is RGB format and OUT OF CMYK COLOR SPECTRUM.

Save the document and reopen the document.

If you are correct, the color value of that rectangle will be automatically converted to CMYK and the out of gamut data for that sqaure will be lost. In other words, your color panel CANNOT identify the color you applied because your color was OUT OF GAMUT and the claim is that the colors are being forced in CMYK Gamut. 

When you export the file or print the file, THEN A VALID CMYK COLOR PROFILE can be used to convert your colors to CMYK. Before then, the CMYK Document Color Mode does not destroy the extra data ffor out of Gamut colors because there is such a wild difference in CMYK Output profiles.

For example, you pick an output profile SWOP which is weak in the Red Orange gamut, for example. Your active document does not change your selected color to cut off the Red Orange colors. It keeps the out of gamut colors. Then, when you change to some other CMYK profile, it has MORE data to work with and can better match the intended output profile. This is the only way that it makes any sense.

So imagine you swapped back and forth between output profiles while working with your art. Eventually you could technically lose all the details in your work because you keep cutting off parts of your gamut that each different profile misses. That would produce the worst possible results.

So since Adobe HAS TO SHOW THE COLORS IN RGB ON YOUR SCREEN, why not just store the RGB data (that they have generally coallesced into the compatible CMYK subset of RGB) up until you are ready for export or print? It helps them, and it makes your prints better.

If you can show me where in Adobe's documentation they claim that using CMYK Color Mode forces adherence to CMYK Color Moel Gamut during the working process (not just during output), I will be convinced and it will be just another reason to avoid the CMYK Document Color mode. I have a list of at least  a dozen reasons to avoid it in the first place, more fodder for the list would be greatly appreciated.

[Ton Frederiks]

Jason, have a look at the gif animation that shows the conversion. Unfortunately Illustrator does not update the changed rgb/hex values immediately, but shows the converted color correctly.

In a CMYK document the colors always get converted to CMYK, using the document ICC CMYK color profile.

[Ton Frederiks]

You are right, color is not very well documented in the help files.

In this help document

https://helpx.adobe.com/illustrator/using/selecting-colors.html

There is only mention of this:

Select colors using the Color panel

1. Select the color mode you want to use from the panel menu. The mode you select affects only the display of the Color panel; it does not change the color mode of the document.

In an old CS6_PrintGuide.pdf

https://helpx.adobe.com/content/dam/help/en/indesign/pdf/CS6_PrintGuide.pdf

I found this note on page 82:

Note: In an RGB document, even if the color sliders are set to CMYK when choosing a color, an RGB color is created.

[Jason Burnett]

Thank you for the clarification. The color picker uses the color you see on the screen. It does not give you an accurate account of the color assigned. For example, do the same test that you did above BUT DON't USE THE COLOR PICKER. You will see that your original color is actually stored as you entered it.

The color picker is flattening the color you see on the screen. This is useful for checking how blend modes work. It does not show the colors assigned to the document, just how they will appear. 

This makes things really tricky, but you can see the advantage of having the added color information available in the CMYK file. It makes it easier for the perceptual rendering intent to modify the CMYK values slightly when two colors are next to each other that would otherwise be cliped to the same CMYK Color. Having that RGB data is critical to optimizing color with the perceptual or vivid rendering intents.

I have to remember that people use use color picker tool and remember to include that as part of the ways that colors get converted. So the only time you get CMYK values when entering RGB values is when you Export, Print, flatten, or use the color picker. The actual assignment of colors preserves even out of gamut color definitions.  Thanks again.

[Ton Frederiks]

In a CMYK document create a rectangle and use the Color Panel to fill it with 0065d7

Create a new rectangle and fill it with white.

Click the first rectangle.

Youn will see that the hex color has converted to the nearest possible in gamut color for (in your example) SWOP: #3567b1

No trace of the original RGB/HEX value you entered to be found.

Illustrator will always convert colors to CMYK and show the closest hex equivalent in the color panel.

[Jason Burnett]

https://www.dropbox.com/scl/fi/umic4q8w280r7chtwqule/Fish-Collapse.ai?rlkey=a95ppc6aira8tuwm9bwj4m9j...

This file contains three fish. They represent what is called color collapse. You shouldn't be able to see the fish in the image in illustrator because, as you say, Illustrator overrides your explicit color delcaration in favor of it's own interpretation of CMYK color.

[Ton Frederiks]

Why shouldn't I be able to see fish when the fish color is different from the background?

Nowhere in this file I see the values you showed.

You've lost me now.