Ahh, the age old question about color adjusting images in RGB or CMYK for print and when to switch to CMYK. Some will argue to switch immediately to confine colors within the CMYK gamut while others will tell you to color adjust and save images in RGB to keep maximum color, than save a converted copy in CMYK.

Either way you have to eventually convert color to CMYK for press. This can drastically restrict and mute certain colors which fall outside the limitations of CMYK. (blue triangle in diagram)

Ultimately, you want to send CMYK PDFs to the printer and unless you're crazy do you want their RIP to auto convert color from RGB to CMYK.

I could talk for days on this subject. Go do some research to make sure your CMYK color setup in Photoshop matches the profile of the press and stock you'll be using. Talk with your printer on the correct settings before converting from RGB to CMYK.

I highly recommend you find books and articles by Dan Margulis for details techniques for color adjusting.
http://www.ledet.com/margulis/2007HTM/ACT06-RGB_conversions.htm

The previous comment was a great explanation of the why, but I have a pretty good solution to the problem. Yes, we all work in RGB because many filters, etc don't work in CMYK mode. But there is a way to see what an image will look like in CMYK while remaining in RGB mode. Under the View menu in Photoshop go under Proof Setup and choose Working CMYK, then go back under the View menu and be sure Proof Colors is checked. This way we get to work in RGB, but we see what our actual colors will be in the CMYK gamut. I hope this helps!

Joel

As Creative_NRG stated, the CMYK color space is much smaller than the RGB color space. Unfortunately, when you're dealing with printing, you must use CMYK to get accurate color results.

The dark/muted/muddy colors you see when you convert a file to CMYK are a result of adding black to the image, as well as the suffering of a reduced color gamut - see the image in the above post.

There's really nothing you can do about this. However, you can "accommodate" for it when you're working on your images.

You don't necessarily have to convert your image to CMYK until the very end, but you can go under Photoshop's View menu and select Proof Setup. In that menu, select either Working CMYK or the CMYK color profile your printer provides you with. Then, again in the View menu, select Proof Colors (Command + Y). This will simulate what your image will look like in CMYK even though the color mode of the file is still RGB (giving you full access to all the filters, etc.)

Hope that helps!

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I'm going to assume you haven't set Photoshop to use Adobe RGB (1998). Check 'Edit - Color Settings' and verify you're using Adobe RGB for print work. By default Photoshop uses sRGB which if you mouse over will give you the following description.

sRGB IEC61966-2.1 - Reflects the characterics of the average PC monitor. This standard space is endorsed by many hardware and software manufactures, and is becoming the default color space for many scanners, low-end printers, and software applications. Ideal space for Web work, but not recommended for prepress work (because of its limited color gamut).

Adobe RGB (1998) - Provides a fairly large gamut (range) of RGB colors and is well-suited for documents that will be converted to CMYK. Use this space if you need to do print production work with a broad range of color.

Also verify your CMYK color settings and Color Management policies.

The gamut issue everyone has been mentioning is dead-on. It's something we print designers have been and will be fighting for a long time. Bright blues and bright oranges are particularly notorious for going muddy fter the conversion.

If you're trying to match any PMS colors, be aware that a very large percentage of PMS color cannot be accurately reproduced in CMYK. You're only fighting the laws of physics when you try.

One thing that can really go wonky when you convert from RGB to CMYK is the way layers interact with one another. Say if you have a layer that has a black area that fades out to transparent, and this layer is on top of another layer. It will look fine in RGB, but give a weird halo effect in CMYK. If you convert the black fade layer to a multiply blend mode, you won't see much difference while in RGB, but it will look much better in CMYK. As a general rule, if you want something to darken what's underneath set your layer (or brush) to Multiply. If you want it to lighten, set it to Screen.

Creative_NRG, I was just about to edit my post to add the flattening deal, and you beat me to it! This is extremely helpful to do. You'll find my HD littered with nearly identical image files that have some indication of RGB or CMYK in the file names.

I'm glad you brought up the monitor calibration/ambient light issue. IMO the ambient light issue is just as important as the calibration. If you're really serious about color work, you HAVE to control the lighting around your workspace. It HAS to stay consistent... so having a window in the room doesn't help. (I have a window, but I keep the blinds closed when I'm working.) You should also position your display so there's no reflections from the room's lighting or any other light sources (like windows).

I also make heavy use of the info palette in Ps to keep an eye on the actual color values in an image. After some experience, you get a better feel for what you see on screen, and what's going to fall out of gamut when you go to CMYK and/or paper.

Thanks everyone,

It's good to have professionals giving me advice, gives me confidence to do my work.

Do your RGB effects in a separate file and then copy those layers over to your CMYK psd file once they are complete. Then you won't jeopardize the color of the entire file.

Place a flattened tif in your ID layout and export pdf/x-1a for best print results.

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Should I also use C=100 M=100 Y=100 K=100 to make sure that my blacks don't get muted, for print? Seems it gets muted on screen when I only use K=100.

Thanks a lot!

I make sure that I have a separate raw version that I get my RGB version that I do corrections to. I use this RGB file to get my CMYK and web versions. I too, label in the file name which version it is.

I was wanting to know myself how to you repurpose a CMYK document to pdf for viewing online and not lose quality in your image and keep the file size low. Is it possible?

One of our printers was able to send me a proof pdf that would simulate how the file would look printed. They called it color check. Were they just pulling my leg?

The thing people are missing here is the science of colour theory. it is all very well explaining Gamuts, but this doesn't explain why CMYK has less colour available.

Both CMY (k) and RGB are tri-stimulus colour spaces, thus having 3 components to make up 'colour'. However one model is additive colour, the RGB model and the other is Subtractive colour, CMY. The theory behind this is best explained when thinking about 'painting with light' in the RGB model.

You may remember from your science days at school shining a red, blue and green spotlight onto a surface and them combining to make white light. This is because the spectral waves of light combine in frequency until the point of whit light resonance.

So, with RGB, the more you add colour, the brighter and more vivid colour you get as you get closer to white light.

However when using paint or in the printers case, ink, you do not see the colour as such. What you are seeing is reflected light from the surface of the ink. In the case of 'red', all light frequencies of the white light around us are absorbed apart from the red frequency at the low end of the spectrum which is reflected. This is known as subtractive light because light is absorbed/subtracted by the surface. Thus adding red and blue on top of each other with ink, darkens the colour as the red absorbs all light apart from red and the blue absorbs all light apart from blue. Add a third colour and practically all light is absorbed resulting in Black (in theory).

In practice you get a grey/brown colour because of the impurities in the ink and paper.
so with the CMY model you should not (in theory) need black, however the 4th ink is added (K to stand for Keyline) to add definition and purity to the blacks and outlines (usually in black).

In a nutshell then your monitor, scanner, digital camera all use additive colour to create images. Your inkjet, offset Litho and Digital presses all use subtractive colour.

In professional digital presses, they use up to 8, 10 or even 12 colours to print with. These artificial colours are enhancers to make up for the subtractive model deficiencies.

Spot colours are added to offset litho processes to provide colours on an individual basis out of the range of the CMYK model. These are often colours like flourescent's, metallic's and particularly pale or subtle colours. You will find that the PANTONE system is the most widely known spot colour matching system. Spot colours add an extra plate, film, and run on a 4 colour press and therefore incur extra costs, so beware when using them...

Enough said.

Joel Mills MCSD
Member of the Chartered Society of Designers

Too good to be true, often is.

If your CS colour settings are set up correctly then there is no real need to save both CMYK and RGB versions of your files.

For the past 5 years we have worked strictly (well almost) in RGB in Photoshop. We import the pictures as RGB into InDesign and let Indesign do the converting. If your CS settings are set up correctly then the conversion you get from InDesign will be the same as what you will get from PS.

Another benefit to this is you can output to various different CMYK profiles from the same RGB pic in InDesign. We have many different profiles for different media/magazines/paper that we use depending on what is called for. But we only have 1 file on our server.

We still use the preview mode in PS - and we are experienced enough to know that we will get muted blues & greens and we take this into consideration.

The only time we save out CMYK versions is if we have some tricky pics that will be run in newspapers and we want to boost the colours after conversion so they are not as dead as most newspaper conversions make them.

I've got a pretty good system for this.
First of all, I work exclusively in Photoshop in RBG mode, for exact reasons listed here in the comments of this post. But I have a folder structure for all my projects that is like this:

Project folder
--->input folder (for storing anything that comes in from clients for project)
--->working folder (this is the primary working folder, with graphics files, etc)
------>support folder (this folder is inside "working" and I save flattened CMYK tiffs in here of...
------------>layers folder (this folder is inside "support" and I save the layered RGB Photoshop files that I create in here. Once I'm done with a Photoshop RGB file, I save it in "layers" folder, then flatten and convert it to CMYK, then "save as" (so it retains the same name, only a different extension of .tiff) as a flattened TIFF file into the "support" folder. I place ONLY flattened TIFF files from the "support" folder into my InDesign documents.
--->output folder (again, inside the root of the project folder, this is the last of the three folders (ie: input, working, output). "output" folder is where I store a record/history of what I've outputted for press/posting and when and to who I sent the files, once approved and ready to "go out" to either press or web server

Thoughts on this system anyone?
I've used it for years in many agency environments and it's worked for me everytime!!