The working difference with RGB vs CMYK modes in Photoshop.
When I started working on my graphic novel called "reMIND", I read that printers needed CMYK files so I decided to create all my Photoshop pages in CMYK only. I worked in this mode for years thinking it was similar to RGB but just printer safe. I Ignored the fact that some of the filters didn't work because I rarely used them. A few years in, I was trying to adjust my pencil lines to be solid black with Levels but could only get a light gray line for whatever reason even though there was solid black elsewhere on my canvas. There was no real reason for this and it drove me nuts when it happened. I mean, printers can print black so what's the problem here, CMYK?
I switched over some of the problematic files to RGB and easily got the lines to turn black. Then I switched it back to CMYK and it finally looked right. I started running into other problems adjusting the Hue/Saturation of specific colors in my CMYK files. Sometimes I'd try to adjust the saturation and my textures would disappear. Sometimes when adjusting a color, I couldn't even get it into the right hue. Or when I'd try to turn the brightness down to black it would turn lighter. I worked around these problems before but now I was starting to get frustrated. I switched my file to RGB again and suddenly after years of denial my eyes were opened.
For some time now I've been itching to do an experiment to see what the true difference is between the two modes. So I recorded myself adjusting an identical file in RGB and CMYK, applying the same adjustments to each. I brought the footage into AfterEffects and time remapped it, lining it up as close as I could. The end result is pretty interesting to me after pulling my hair out for years over why I couldn't get my stupid colors to look right. I hope it helps you decide which mode to work in and why. When I first wrote my list of things to know before starting a graphic novel, I told everyone they should work in CMYK. I now think the opposite is true and updated the list to reflect my new opinion.
My apologies for the funky sound mix. I accidentally said CMYK instead of CMYK for the whole video and had to splice in the corrections later. I know a few are still in there somewhere but who cares. Hope you enjoy the video. Right click it to watch on YouTube for the best resolution or full screen.
Notice how the textures turn into flat colors in CMYK when they are adjusted with an overlay. The other thing that drove be crazy was towards the end of the video, turning plain texture to white and still having dark spots or turning it to black and having uneven blacks. It's not as clear in the compressed video but the CMYK file has blacks and dark blacks for some reason. I mainly wanted to show the basic differences with the modes and why it's just easier to use RGB and convert your flattened file to CMYK when you are finished. Always save your master file with all the layers in RGB though.
Hope this helps!
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Very informative. Is it still the case that printers need CMYK? Could the problem be a glitch with Photoshop? I wonder what happens if you do the same side by side comparison using GIMP?
I've never tried GIMP. Well, once you learn Photoshop, it's kinda hard to use anything else. For the most part, printers still use CMYK files if you want it printed professionally. I know some cases, like http://Ka-Blam.com , that prefer RGB files. But they only do print on demand. I've used them before and really like their service though. As for reMIND, I wanted to print it hardcover with traditional offset printing which would require CMYK files for the printers.
It might be a glitch with Photoshop but everyone who I've talked to says it's always been really different. I assume one day they will figure out how to make it closer. But the one thing that will always be a concern is making sure your colors are in the CMYK range. RGB has a much larger range of colors (mainly super bright ones)
Yea, I work completely in RGB. CMYK causes too many issues… and the files are larger!!! Being in the animation/film industry I've always worked with RGB anyway, but when it came to doing comics I just couldn't deal with the lameness of CMYK. Thankfully we live in a wonderfully advancing modern age where printers now will/can print in RGB. I love technology!
However, if you still need to output in CMYK but want to work in RGB, I would suggest that you use the lovely little tool in Photoshop known as "Proof Colors". It can be found under VIEW, Proof Colors. The settings/choices are under Proof Setup, where you would select "Working CMYK". What this does is allows you to work in RGB, but flip back and forth with the proof view to see how it effects your colors!
In the video I talked about the Proof Colors/ Working CMYK thing towards the end. But maybe I’m not following exactly how I can switch it back and forth to see if my colors are safe. I have Working CMYK on all the time. Is there a button I can push to switch it back and forth like you said or is it just a matter of having always on?
When you convert your images from RGB to CMYK, the reason they go 'flat' or lose intensity has more to do with the specific profile you have set for the conversion. The reason Ka-Blam requests files in RGB is so the raw file can be converted using their printer's specific colour profile. Most of the time they will try to color match as best as possible to the monitor settings.
Everything that is printed relies on a CMYK base. It is called subtractive colour – where you remove pure colors (Cyan Magenta Yellow and Black) mixed together by percentage to make a solid colour. RGB uses additive color, where you start with pure black and add varying intensity of three colors of light (Red Blue Green) to create a color.
Another reason why your colors appear to go flat is 'gamut.'
The human eye can see millions of colors. What you see on screen is an approximation of those colors, based on a gamut specified by the intensity of light created in the RGB space. What you see in print is an approximation of those millions of colors based on a gamut specified by the percentages of mixed inks. This gamut shrinks significantly when you compare RGB and CMYK. There is no luminescence in opaque inks, but you can get it with transparent light mixtures in RGB.
Regardless of how you draw and color your work, when it goes to print, it will be converted to CMYK. An 'RGB printer' is a CMYK ink printer that approximates the color space in RGB and reproduces it to the best of its visible ability. Photographers go for this type of printing to keep the truest colors possible.
Your other option involves hexachrome printing, which is a Pantone proprietary type of printing that uses 6 inks rather than 4. But its mega-expensive.
I deal with this crap on a daily basis, so if you have any questions, feel free to shoot them my way.
Thanks for this nifty breakdown. I have very little understanding of how this stuff really works being pretty new to it all. I understand how the colors can have a larger range in RGB and I think I mostly understand why. Especially hearing everyone talk about it here. It's interesting what you said about Ka-blam though, how they still print in CMYK even though they want you to deliver RGB files.
So my big question to you is this….
Aside from the differences in RGB and CMYK in how they are created, my real question in the video is why it's different in Photoshop while trying to use filters. The differences go way beyond what CMYK can handle and more into the world of programming it seems. For instance at the end of the video where I'm just adjusting the CMYK file with the lightness and darkness slider, why does it not go all white when I move the slider to the light side, it keeps leaving black areas in the texture. Is this more about what you are saying with the specific profile you have set for conversion? I might be totally misunderstanding that line. But do you see my question?
Ah, color theory. Actually, this is something of a problem for me, as I have light-sensitive eyes that, over the years, have made it very hard fro me to distinguish fine shades of color, especially reds and greens. It's not colorblindness exactly, at least not as my opthalmologist describes it, but it can be trouble, for sure. And of course, where is my comic set, but in a jungle. Green. Bane of my existence!
RGB vs CMYK is a really good topic to get into, though – the mixing of liquids to produce their opposite colors, versus the mixing of light to produce the illusion of positives! RGB on a TV or Computer screen will always appear far more saturated and pure to the human eye as it's direct-wavelength light being sent straight to the retina, while CMYK relies on the reflection of light off of an opaque surface, and thus mixes in all the subsidiary colors that a given light source contains. Actually, if I understand it rightly, RGB and CMYK mixing is basically bridging the most fundamental disconnect between print and screen, i.e., that a Computer has to simulate CMYK (hence the lost options in Photoshop) and the printer has to approximate RGB (hence the wierd things that can happen when color management isn't properly calibrated).
–M
It’s funny you say you have light sensitive eyes. So do I. Maybe not at the level you are talking about though but I sure do turn down the brightness on my computer screen to it’s lowest settings and it’s still too bright. I wear sunglasses in the shade not just because I’m too cool for school. It really is bright.
In fact this scared me away from color for a long time because I just felt like I would never be able to get it. But the more I study it and practice it the more comfortable I’m getting.
Actually, for some years I was misdiagnosed as having macular degeneration. It’s actually not that – it’s retinal photosensitivity. Actually rather common. I also wore dark glasses pretty much everywhere for some years, even at night. (Nobody EVER mentioned that goddamn song, either. Except every five freaking seconds.) It’s only recently that I’ve been able to stop doing so. But yes. It can cause serious trouble when your retinas break down, particularly the cones. I still keep my apartment pretty dark. Though on the plus side, this saves on electricity, and my cat can see in the dark anyway so she doesn’t mind.
Interesting though – I’m hearing more and about artists who have this problem in one form or another. I also steered clear of color for a long time for this reason. And I still have a feeling that my colors are rather more “pushed” than I wish they were, and my color compositions tend to appear rather dark to some people.
–M
I believe that part of the problem with CMYK in Photoshop may be that I think Photoshop is actually using a third colourspace: LAB. The problem with changing the lightness/darkness in CMYK is I think due to the additional complexity of specifying a particular colour in CMYK. Increasing the fuzziness of your filters will help, I find a value of 50 works quite well.
Part of the change in appearance when converting between the two is likely because your monitor uses RGB output. To show CMYK it's already having to convert the colour which can affect the way it comes out.
Regarding printers, I'm not sure what they're doing with the RGB files but all Litho and Digital printing that I've heard of is CMYK only. If they're accepting RGB files, it might be that they're converting it themselves which isn't ideal as it takes your creative control out of the loop. My only suggestion is to always ask for a test print first, that way you know what you're getting.
Yeah I’m not convinced in using a printer who just wants the RGB files to convert themselves. I like Ka-Blam for simple jobs but reMIND is not going to be simple so I know I need to learn more about this stuff or hire someone to help me do it the right way without trial and error.
Be careful, converting RGB to CMYK when you’re done is not as straightforward as that – it will add black to all your hues and the printed result will look quite a bit darker than intended. I speak form experience, after one of my books was printed far too dark I got guidance from my printer to avoid that problem, and now I can get my printed pages to look exactly as intended. The proper way of converting them is to get a profile from your printer and File > Convert to Profile then select the profile form the list. The page will look slightly different on your screen but don’t worry about it – it’s just the screen. If you work with an offset printer as I do, they can do the conversion for you but it costs extra, which is why asking for a conversion profile is a good idea.
It’s also a good idea to separate your text from the background, when it’s shown on white (as in speech bubbles) and make sure it’s pure K. It’ll look grayish on your monitor but when printed, it’ll be printed in just one pass of black and so be safe from any fuzziness that can occur if the registration is slightly off.
Man, there is just so much to learn here. I have a feeling that I’m going to need to hire someone to make sure I am doing this all right. Or maybe I’ll have to pay the printed extra money to do it for me. Thanks for your comment and suggestions!
Interesting but also very confusing after reading through all the replies. In the case of digital printing should one include a color profile at all? And if so which one? I have some tiffs being prepared for digital printing but I'm totally confused as to which color profile to include. I hope some of you guys can shed some light on this :-)
I'm no expert on this as you can see from my post and comments but from what I've heard, if you are printing digitally then there is less complications to the printing. You might try to email Drezz and ask him. He said he deals with that stuff all day.
It also seems like every printer has it's own way of doing things and their own color profile settings. Your best bet would be to ask the printing company you are using of getting the specs straight from them. Sorry I can't be more helpful.
That's cool I'll just go straight to the source. But yea setups vary from printer to printer I just thought maybe there was some "standard" to go by. But I'll find out soon enough, if I don't drown in printing tech talk first :P
Holy crap. This is super helpful. For the past few years I've been unsure about what to work in, even after a bunch of research. Working artists all tell me different things…but this seems pretty clear. I really don't see that much color difference converting from rgb to cmyk, so it makes sense to just use rgb.
Thank you sir.
I was actually one of the first people to color a comic book with Photoshop. It wasn’t my idea. I was an Amiga user at the time, but I was the only person they could find with enough experience using digital art tools. I actually did a few tricks with a program called Brilliance on the Amiga, but I quickly warmed to the rich set of tools offered by Photoshop. At the time it was version 2.5 on Windows 3.11 running on a 486 DX2-66 Dell with only 16mb of RAM. Just running a blur filter could take all night to process, and in the end we had to half the resolution of the pages to make things work. I was lucky to get trained in Photoshop at the time as a perk of that job, and a lot of the graphics I made for that project never made it into the final version because the people doing it wanted flat color, and the tools in Photoshop immediately made me want to be Richard Corben. ;)
Anyway, in various projects since then, several of them comic strips or books, I dealt with these issues concerning RGB and CMYK. I can tell you quite a bit about this.
Obviously the reason a CMYK file is larger than an RGB file is because the CMYK file has four color channels (what we used to call “plates” in printing) and RGB has only three color channels. Each color channel is essentially a grayscale bitmap representing one color element in the image or page. You can actually do some pretty nifty tricks manipulating the color channels in CMYK, but that’s a topic for another time.
CMYK is additive color, while RGB is subtractive color. If you completely saturate a CMYK image you should get black, but in more realistic terms you get the equivalent to the painter’s V. Mucky Pig, which is short for very mucky pigment, a grayish brown. The RGB model works in reverse. The absence of light becomes black, while the combination of all three colors makes white. These two models are different enough to cause some issues in conversion. I should also mention that earlier versions of Photoshop had slightly less effective conversion algorithms than current versions, and there are actually entire software products designed for the purpose of converting from one mode to the other with more accurate and vibrant reproduction. Many professionals spend some time tweaking the color balance of an image after conversion from one mode to the other.
There are two primary models for conversion of RGB to CMYK. I actually used to have a nice big glossy poster devoted to this topic, believe it or not. The two primary models are GCR and UCR. GCR stands for Gray Color Replacement, and UCR stands for Under Color Removal. Neither is considered a perfect process in principle, so conversion in software tends to utilize a combination of both.
Gray Color Replacement is based on the idea that grays in an image should be comprised of a balance of cyan, magenta, and yellow, not just a gray halftone of black ink on the K plate. Under Color Removal is based on the idea that you should try to replace as much of a color with black ink as possible to get the right balance.
I don’t know if you’ve ever experimented with printing at all, but basically if you try to put 100% C, M, Y, and K inks on the page, you get a disgusting smeary mess of ink that won’t make anyone happy. On the other hand, if you use only the black “K” plate for solid black areas, chances are the ink isn’t going to be the expensive, high quality stuff, so you get faded grayish garbage instead of a nice solid black area. Old fashioned comic books sometimes would end up with ugly blacks because of this problem.
The way comics used to be colored was a much trickier process. An artist would color a black and white copy of the art with markers, watercolors, or whatever, and that was called “indications” in the industry. These indications were used as a guide for the person who had to cut film and lay it out to make the correct colors on each plate. They used charts to figure out which shade of gray would be the right one to combine with the other cut areas of film on the page to make the correct colors for each area. It was a huge pain in the ass.
One problem with GCR that could happen was misregistration. You may have noticed the little registration marks on the pages. They sometimes look like little color bars next to a crosshair. The crosshair is where everything is supposed to line up, and the color bars are there to show what each plate’s ink looks like by itself on the paper in use. If the plates aren’t in alignment with each other it’s always a problem. It’s worse with GCR because the black and gray areas on the page are actually a combination of all the colors, so the edges will look like utter crap when they’re out of alignment. With UCR you don’t have that problem because there shouldn’t be any color in your grays or blacks, but it depends on strong black inks to get good saturated blacks.
I always used to wish I could create my own conversion software using special targets for each equivalent color value. It was frustrating working with the defaults, especially when you don’t have the perfect color profile for the conversion. It’s entirely possible in Photoshop for your color profiles to provide seriously inaccurate representations of what your CMYK print will look like, and it uses those profiles for the conversion process. This has led to several disasters in the past which I won’t rehash here.
Anyway, the solution to using CMYK color instead of RGB is to create your own custom CMYK color palette. You can’t just create one in RGB or LAB color and expect it to convert well to CMYK. If you want total control over how your colors print in a comic book, that’s how you do it.
With your own custom palette you can, for example, create two different kinds of black, one that is made only of black ink from the K plate, and the other with a combination of black and color plates.
As I remember it, for some reason Marvel used to want their color work done with the black at 600 dpi as a black and white bitmap (since the linework isn’t shaded grayscale art, so the ink is either there or it’s not) and the color could be done at 300 dpi. They wanted a pure black plate. I doubt they have the same rules now, quite a few years later. They also used to have issues with the colorists dropping the blacks for effect, and I see that being allowed a lot more in today’s comics. I guess they finally got the point all the colorists were trying to make about that.
The main filters you will lose by creating your work in CMYK instead of RGB are the ones that make their calculations based on the behavior of light, such as lens flares. That’s why some don’t work in CMYK. They’re playing with the model for light itself.
It would be nice to be able to create your own color profiles, and there is quite a bit of control available in Photoshop if you want to play with it. You can make it convert from one mode to another in a more satisfying way, but unfortunately it won’t be as user-friendly as an artist would like. Personally I’d like to define the poles of a color gamut for each model. Cyan = this in CMYK, this in RGB, Red = this in CMYK, this in RGB, etc.