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RGB or CMYK

Nicholas Bailey , May 15, 2011; 02:18 p.m.

Hi

I have always supplied clients with RGB files on disk ready for what ever their needs printing etc.. but should I really be supplying them with a cmyk files or doesn't it really matter....I have just shot a wedding and when I use photoshop I switch to cmyk to have more control over retouching..should i convert them back to rgb..

thanks in advance
nik

Responses


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Leigh B. , May 15, 2011; 03:22 p.m.

Active displays (computers and such) are done in primaries (RGB).

Printing is done in secondaries (CMYK). The K (black) was added because you can't get a good clean black by mixing Cyan, Magenta, and Yellow inks.

So the answer to your question depends on the client's application. I would supply both versions of each image.

You can set up two directories on the CD, one for Display and one for Print.

- Leigh

Tony Bynum , May 15, 2011; 03:25 p.m.

forget the cmyk, that's for offset printing. . . Unless youre making books or posters, you should not be in the cmyk color space at all . . .

Leigh B. , May 15, 2011; 03:29 p.m.

CMYK is used for all printing, not jut offset.

All color inkjet and laser printers use subtractive media, as they must.

The happy couple certainly may wish to print books or posters or similar displayables.

- Leigh

Mark M , May 15, 2011; 03:51 p.m.

I would never, ever, supply CMYK to anyone who did not ask for it with a good reason.

Although printers do use subtractive color, most printers that are not offset presses will have more than four inks and will have substantially larger color gamuts than CMYK. Sending CMYK to these printers makes it impossible to take advantage of this larger gamut and you can't get everything the printer has to offer. This is why most printer drivers expect RGB color.

Even if you know the final output will be CMYK offset, it is still better to use an RGB working space until the last moment. All CMYK is not created equal and offset presses are notorious for their variability—the color is affected by humidity, paper variation, ink batches, etc. which is why many printers will want to deal with the RGB->CMYK conversion themselves.

Nicholas, I can't say it strongly enough, you should learn to do your editing in RGB. Converting everything to CMYK in the beginning throws away a huge amount of color information that you can't get back and you needlessly confine yourself to a very restrictive color space.

Ellis Vener , May 15, 2011; 05:17 p.m.

If they can't supply you with a CMYK profile and your system (display and printer) is very well color managed don't do a CMYK conversion. Why the pritner/ Becasue you will also want (maybe even need ) to supply them with a "match print" for the client to compare their proffs to your match print. Jeff Schewe ( who knows more about this than 99.999% of the people on this board -- the .001 is reserved for Andrew Rodney) also recommends that if you do the CMYK conversion you delivered o n a CD-R or DVD-R so the printer can't come in and mess around with the files you deliver.

All color inkjet and laser printers use subtractive media, as they must.

Mostly true but inkjet printers do an on-the-fly internal RGB > CMYK conversion . If you send an inkjet printer a CMYK file it will first convert it to an RGB color space RGB and then convert to its internal CMYK color space.

Joseph Wisniewski , May 15, 2011; 10:00 p.m.

Nicholas, there is no reason to switch to CMYK, you will not get "more control over retouching", you will simply make a hard-to-fix mess of the colors. Seriously, tell us what "retouching" operations you're performing where you believe you're getting "more control", and we'll tell you better ways to do it without ever leaving RGB.

CMYK is totally "device dependent", you're creating images for a machine that, as others explained, no one will be printing on. The conversion from CMYK back to RGB is like attempting to "unbake a cake". Some parts can be analyzed, some parts will be wrong. The end result is banding, color errors (pretty massive ones in the more saturated colors) and all sorts of other problems. CMYK is an extremely advanced mode of working, and requires you be very familiar with a particular printing press.

For God's sake, don't deliver any CMYK to the client.

Leigh - CMYK is used for all printing, not jut offset.

Actually, current decent inkjets typically use things like CMYKRG or CMYKOG to increase gamut. But there's no way to access the low-level color (CMY, CMYK, CcMmYKkk, CcMmYKkkkOG (think that's the worst) with the printer manufacturer's drivers. You need a RIP program and the knowledge to use it. Something tells me that the OP, on his first wedding, with the whole "I switch to cmyk to have more control over retouching" thing is nowhere near ready for that.

All color inkjet and laser printers use subtractive media, as they must.

Actually, pigment printers have an interesting mix of additive and subtractive characteristics, as they must. This has been well documented for, literally, millenia, because it's the same problem you see mixing pigmented paints. It is why the ancients strove to solve the "problem of green" and a bright cookie like Aristotle declared that there had to be 6 true primaries: red, blue, yellow, green, black, and white, because there is no "three primary" solution to the problem of opaque pigments.

That is why you can increase gamut by adding colors like orange, green, red, or blue to the inkset. Oh, and in general, cyan, magenta, and a "wide band" yellow are referred to as "subtractive primaries", while orange, a narrower band yellow, indigo, violet, and purple are "additive secondaries".

The happy couple certainly may wish to print books or posters or similar displayables.

Well, unless the happy couple has a press of their own, and specifies the particular CMYK that they need to the photographer, they're in a world of hurt if he delivers CMYK instead of RGB. They will no longer be happy. Seriously, the book company or poster company will have their own RIP set up their own way to convert incoming RGB in a known color space to a CMYK that is suitable for their press.

Andrew Rodney , May 16, 2011; 09:50 a.m.

Actually, current decent inkjets typically use things like CMYKRG or CMYKOG to increase gamut. But there's no way to access the low-level color (CMY, CMYK, CcMmYKkk, CcMmYKkkkOG (think that's the worst) with the printer manufacturer's drivers.

Exactly. While the post saying “all printers use CMYK” (or a multiple mix of colorants) is true, its what color space you send the print driver that’s the important question. Most of the desktop printers expect RGB data to do their own proprietary conversions to CMYK or CcMmYKK, CMYKOG etc.

Stuart Moxham - Finland , May 16, 2011; 03:45 p.m.

Why do you convert your images to CMYK for retouching. You should be able to do all of your post processing Adobe RGB color space.

Bill Tuthill , May 16, 2011; 11:27 p.m.

CMYKRG = CMYK red green, CMYKOG = CMYK orange green. I believe our beloved Canon inkjet has CcMmYKk where c is light cyan, m is light magenta, and Kk are dye and pigment black. What is the second k in CcMmYKkk?

Also, don't some printers accept ProPhotoRGB for wider gamut printing?


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