RGB vs CMYK

[Scott Johnson]

I think working in CMYK was more beneficial on books with low ink limits (less fuss with color shift), but for the high-end stuff, working in RGB and converting sounds like the way to go.

Thanks, Chris!

-- Laura

I still don't understand the advantage of working in RGB and converting. Could someone explain this? Why is that method "the way to go"?

[John Rauch]

I think working in CMYK was more beneficial on books with low ink limits (less fuss with color shift), but for the high-end stuff, working in RGB and converting sounds like the way to go.

Thanks, Chris!

-- Laura

I still don't understand the advantage of working in RGB and converting. Could someone explain this? Why is that method "the way to go"?

The simplest way I can explain it is that RGB is the way light actually works. You can blend between colors much more easily and naturally in RGB than in CMYK because RGB is the way the world actually works. CMYK is the simplest way there is to duplicate it with ink. RGB is based on adding more of each color until they make white. Adding C,M,Y, and K results in a muddy unnatural blend that eventually makes black. Here's an example of what I mean. The first blend is from Red to black in RGB. The second is from the same Red to the default CMYK Black with it's generic undercolor (in CMYK). The third is from the same Red to 0,0,0,100k also in CMYK. Obviously, the 1st one is most accurate to the way color blends in real life also making RGB the most natural and easiest way of immitating real life. Hope that helped!

[Sweeney]

I still don't understand the advantage of working in RGB and converting. Could someone explain this? Why is that method "the way to go"?

RGB gives you a much richer, broader range of colors. Yes, a lot of them are out of gamut, but if you work directly in CYMK, you have a much smaller range of colors and tones.

CMYK gives you a max of 10 million colors. RGB gives you 16.7 million.

Also, a lot of filters are RGB mode only - they don't work in CMYK.

CMYK files (for coloring, with an extra alpha channel for lineart) are 25% larger, requiring more RAM, HD space, scratch disk space etc.

You also get better results with more finesse doing global color corrections in RGB than in CYMK, because of the broader range of colors. By Global color corrections, I mean using Levels, Curves, and other similar adjustments on the entire file, rather than a selection.

[Scott Johnson]

But I still don't get it. I understand working in RGB if you are creating Websites, because monitors use RGB, but if you are coloring for print then you are creating for CMYK. What difference does it make how good it looks on your screen if the end result will be printed in CMYK anyway?
Are you guys saying that if you create a gradient in RGB, then convert to CMYK, the end results will be better looking in print than if you created the same grad in CMYK to begin with? I was under the impression that any colors out of the CMYK gamut will be lost when you convert. (Thus created the color shift.) I used to do my digital paintings in RGB with the CMYK preview always on, but I didn't see any difference between working that way and simply working in CMYK to begin with. (By the way Sweeney, those filters are available in CMYK, you just can't apply them to all 4 channels at once. They can be applied to the channels separately.)

[Sweeney]

It makes a difference - many people may not see it, but it does.

By the time a file has gone to print, lots of details and color are lost.

RGB (16.7 million) -> CMYK (10 million) -> Film -> Plate -> Paper.

I no longer have the formulas for figuring out exactly how many shades are possible depending on the linescreen, but printed CMYK has far fewer colors than the original CMYK file. On most papers, and presses there is no difference between 0% color, and 2%, just as there's no difference between 98% and 100% ink.

Working in RGB gives you more colors than working in CMYK. Converting to CMYK as the last step, rather than working in CMYK gives you a better, richer range of colors that isn't possible working in CMYK, simply because you have 65% greater colors. The more colors you start with, the more that will end up on the paper, even though you've gone from tens of millions of colors, to tens of thousands of colors.

Think of it like painting with oils. Theoretically, you can create all the colors you need for print with just Cyan, Black, Magenta and Yellow. However, how many painters do you know that use *just* those colors for painting book/comic covers?

Some painters have dozens or more different tubes of oil paints that are outside the CMYK gamut. Why? because they get a greater range of colors, tones that make for better blends of color.

That's what RGB gives you over CMYK.

I made a simple gradient, in RGB using CMYK colors (not out of gamut). I made the same simple gradient with the same colors in CMYK.

I also took the RGB version, converted to CMYK, then back to RGB (Converting from CMYK to RGB doesn't increase the range of colors, it's just done because you can't really show RGB on websites).

It should illustrate the difference for you.



As you can see with the version done in CMYK, the colors tend toward greys in the middle where the two colors blend. In RGB, they are still vivid, bright colors, not desaturated/muddy.

Even the version originally done in RGB, converted to CMYK (and back) shows a greater range of color than the original CMYK (this has the original CMYK gradient below for comparison).

I hope this explains it a little better.

[Laura]

I gave the conversion a try. It's fine for pages without a lot of red. That's what prompted me to start working in CMYK anyway -- Astonishing X-Men requires a lot of red.

I converted a very red page from totally legal CMYK to RGB, flattened the file, and converted back to CMYK -- and the whole thing went orange. What the--? Grr!

-- Laura

[John Rauch]

Laura,

I don't know if it's still in the manual or not, but there used to be a warning about switching back and forth between color modes. The more you convert, the more color you're going to lose.

[Scott Johnson]

Okay, I've never had anyone explain that before, so now it makes more sense to me why so many people work in RGB even if the end result is CMYK printing.

I'd like to hear more opinions on this. I know a lot of artists work in CMYK (Dave and OBERGEEK come to mind). For comic coloring I've been using Dave's Simple CMYK Layer Setup because I found it a lot easier and less confusing to work in than the RGB methods I've seen, especially where hold/knockouts, special effects, and trapping is concerned. But much of that may come from my comfort with layers and unfamiliarity with channels.

[Reber]

I don't know all the technical mumbo jumbo when it comes to Photoshop and printing. What I do know is what works for me and what doesn't.

For me it is easier to do effects in RGB than in CMYK. Some modes just do not act the same in both modes. Sceen and multipy for example is just about useless from what I can tell in CMYK. It comes down to what techniques you use to get your final result. If you approach your work as a painter where you build up your colors and pick every color you use then CMYK is probably fine. If you rely on the tools to build up your colors then RGB is the better mode. I'm a mixture of both, but I use the tools to get my effects and they work best in RGB.

[Reber]

Okay, I've never had anyone explain that before, so now it makes more sense to me why so many people work in RGB even if the end result is CMYK printing.

I'd like to hear more opinions on this. I know a lot of artists work in CMYK (Dave and OBERGEEK come to mind). For comic coloring I've been using Dave's Simple CMYK Layer Setup because I found it a lot easier and less confusing to work in than the RGB methods I've seen, especially where hold/knockouts, special effects, and trapping is concerned. But much of that may come from my comfort with layers and unfamiliarity with channels.

I use the same setup in RGB.

[John Rauch]

If I were working on a cell shaded book or something with flat colors, I'd definetly use CMYK for absolute color accuracy; but if I need to blend colors and get the most natural transitions without using a palette of 6 swatches for every blend, I'm gonna stick with RGB.

As far as line holds, special fx, trapping, etc. goes...it's very simple to do these things in RGB. My first 4 years or so, I worked strictly in CMYK and I actually think it's much easier to do effects like glows in RGB. You never have to worry about whether or not your black can handle a good glow without greying out because in RGB there's only one way to make black. Black is black is black. In CMYK, if I wanted to glow Red into Black, I would have to fill an area of my line art with a Red undercolor so it could handle the glow by removing K. Otherwise, the shift between say 54, 43, 41, 100 (my generic black with undercolor in CMYK) and 0,100,100,0 (pure CMYK Red) would be very dull and turn grey in the middle. Now, I have to worry about finding some way to blend the Red undercolor with the Grey undercolor so you can't see it underneath the black once it prints. Then, if I have to glow different colors in different areas, I have to worry about it all over again...not to mention the pain it's going to be to glow into the regular colored area because who knows what might happen there. What if the Red object I want to glow is sitting next to something Green? That's not going to look at all like a realistic lighting effect no matter what blend mode I use, so the set-up for making that blend look right is an even bigger pain then going straight into black.

Anyway, I'm rambling and I don't know if any of this even makes sense without illustrations, but hopefully it helps atleast a little.

[Laura]

I've been a diehard RGB colorist since day one, but I started coloring in CMYK after I left Crossgen because I knew I couldn't control the output as readily, particularly with Wildstorm's 240% ink limit.

I'm still getting used to it. I can actually set my brushes to Screen and Multiply and get painted effects similar to those in RGB, without worrying about gamut. And I've been pretty happy with the color output overall -- I just saw some print proofs for Astonishing #1 and for I Am Legion (both of which I did in CMYK), and the color held up really well.

I can't run certain effects, though, like Emma Frost's diamond-skin effect. For that, I actually copy the figure of Emma, open it up in a new file, convert it to RGB, run the filter, and then paste that back in on a layer in my original document.

I guess I'll keep playing with it. I have to be mindful of the different ink limits for each studio, though.

-- Laura

[Scott Johnson]

I don't know all the technical mumbo jumbo when it comes to Photoshop and printing. What I do know is what works for me and what doesn't.

For me it is easier to do effects in RGB than in CMYK. Some modes just do not act the same in both modes. Sceen and multipy for example is just about useless from what I can tell in CMYK. It comes down to what techniques you use to get your final result. If you approach your work as a painter where you build up your colors and pick every color you use then CMYK is probably fine. If you rely on the tools to build up your colors then RGB is the better mode. I'm a mixture of both, but I use the tools to get my effects and they work best in RGB.

Yeah, I pretty much pick my colors as I go. I'll occasionally try Screen and multiply, but for the most part I find it very unpredictable...I often find myself screening and rescreening and rescreening...its easier to simply pick the highlight and shadow color I want.

I use the same setup in RGB.

Would it be possible to see that setup? What color black do you use for the lineart layer? What mode is it set on? Are there any other differences to the CMYK model?

I can't run certain effects, though, like Emma Frost's diamond-skin effect. For that, I actually copy the figure of Emma, open it up in a new file, convert it to RGB, run the filter, and then paste that back in on a layer in my original document.

Have you tried running it on the individual channels in CMYK? If not it's worth a shot.

[Scott Johnson]

If I were working on a cell shaded book or something with flat colors, I'd definetly use CMYK for absolute color accuracy; but if I need to blend colors and get the most natural transitions without using a palette of 6 swatches for every blend, I'm gonna stick with RGB.

As far as line holds, special fx, trapping, etc. goes...it's very simple to do these things in RGB. My first 4 years or so, I worked strictly in CMYK and I actually think it's much easier to do effects like glows in RGB. You never have to worry about whether or not your black can handle a good glow without greying out because in RGB there's only one way to make black. Black is black is black. In CMYK, if I wanted to glow Red into Black, I would have to fill an area of my line art with a Red undercolor so it could handle the glow by removing K. Otherwise, the shift between say 54, 43, 41, 100 (my generic black with undercolor in CMYK) and 0,100,100,0 (pure CMYK Red) would be very dull and turn grey in the middle. Now, I have to worry about finding some way to blend the Red undercolor with the Grey undercolor so you can't see it underneath the black once it prints. Then, if I have to glow different colors in different areas, I have to worry about it all over again...not to mention the pain it's going to be to glow into the regular colored area because who knows what might happen there. What if the Red object I want to glow is sitting next to something Green? That's not going to look at all like a realistic lighting effect no matter what blend mode I use, so the set-up for making that blend look right is an even bigger pain then going straight into black.

Anyway, I'm rambling and I don't know if any of this even makes sense without illustrations, but hopefully it helps atleast a little.

I appreciate your input, but I honestly don't understand what you're trying to explain here. Maybe I need pictures.

(By the way everyone, thanks for tolerating the noobie-like questions. The methods and requirements for my illustration work are not the same as a comicbook page setup.)

[ChrisCox]

When working in CMYK - you can put down any ink mixture you want. There is no way to enforce the printing ink limits. And dot gain can do funny (non-linear) things to your colors, especially in gradients.

When working in RGB - the RGB colors will be converted to CMYK at the end, and the conversion can enforce the ink limits. The downside is that you don't get to make choices about pure black or rich black -- all blacks are converted the same. (now I just need an easier way for you to dial in the ink limit and build your own profiles)

Also, if you want to repurpose the art (posters, print on better paper, web, etc.) down the road -- it's a whole lot easier with an RGB master than with CMYK targetted to a specific press,paper and ink combo.

And many of the special effect filters work differently when applied to channels than when applied to a full color images.