Participating Frequently

Question

Converting from RGB to CMYK makes the image dull. How do I fix?

Forum|Forum|16 years ago
April 21, 2010
7 replies
156917 views

I have an image that has a really bright vibrant blue in it. When I convert it from RGB to CMYK, it gets pretty dull. Is there a "trick" or something to do to a file after converting to CMYK to bring back some of it's vibrancy?

FAQ

Dave Creamer of IDEAS

Community Expert

@Test Screen Name asked a reasonable question--how would you change the answer? Additive vs subtractive color is a matter of physics--even Adobe can't change that.

Instead, you start name calling.

David Creamer: Community Expert (ACI and ACE 1995-2023)

S

Sharingene

Participating Frequently

Hello, I just happened upon this discussion after trying to solve the same issue with a brochure I am sending to UPrint. The initial proof was disappointing to say the least. I have spent the weekend trying to educate myself on color-management--oh my goodness! But your suggestions here have already helped make a difference with the first converted CMYK image I am working on--so THANK YOU!

Question on workflow... so do I convert my sRGB to CMYK, work to fix different color issues using some of the methods above, then what? Where does the printer's profile come into play during all of this? UPrint told me for offset printing they use US Web-coated SWOP v.2. Just not sure what to do with this information--I guess it's used in soft proofing but sure how all this works. If I soft proof and it's still not looking right, am I able to edit with their profile turned on some how?

Also, should I get a profile for the paper I'm using as well? --Although I've read somewhere it's hard to have your monitor replicate paper because monitors are so bright....

Oh, thought I'd add a tip to this discussion which might be sort of a "no-duh--well that's obvious" tip to those of you who are able to answer all these questions, but might help those who are new to all of this... When you're still in RGB but you want to see what colors are going to be "out of gamut" once you've converted to CMYK, click Control+Shift+Y (also found under View> Gamut Warning). It's very handy in knowing where to focus your attention once you've converted to CMYK.

Thanks again for the great info in this forum!

P

Printer_Rick

Inspiring

Sharingene wrote:

Question on workflow... so do I convert my sRGB to CMYK, work to fix different color issues using some of the methods above, then what? Where does the printer's profile come into play during all of this? UPrint told me for offset printing they use US Web-coated SWOP v.2. Just not sure what to do with this information--I guess it's used in soft proofing but sure how all this works. If I soft proof and it's still not looking right, am I able to edit with their profile turned on some how?

Somebody may have already mentioned, in Proof Setup select the appropriate CMYK profile. If the image is already CMYK select the profile of the image. Then enable "Simulate Paper White."

When you do this the image will look flat and dull. But at least it's a more honest appearance, provided your monitor setup is correct.

Monitor white point color temperature (5000K, 6500K) can affect the display of white points in images too, although in theory it shouldn't. Maybe others can offer some insight on this.

Anyway, the idea behind "Simulate Paper White" for CMYK is pretty neat. The paper white is built into the ICC profile. It is expressed in Lab values.

Under normal circumstances, and for file conversion purposes the paper white cannot be allowed to be a factor. After all – the CMYK can't possibly be brighter than the paper it's going on, right? So in a file conversion, the white is regarded (and should be regarded) as L100 a0 b0.

But in reality the paper does have dullness and a color. To see this, fill a CMYK space with white. Now Convert to Profile. Select Lab. Absolute Colorimetric intent.

The resulting Lab honors the true color of the paper. For US Web that ends up being L89 a0 b4. Dirty and a little yellow. The truth hurts.

This is what's going on with "Simulate Paper White", an absolute colorimetric soft proof conversion. It's a neat trick but a lot of people don't use it because it makes an image look like CRAP.

C

Colin M

Participant

If you know you'll need to be dealing with CMYK on a regular basis, it's well worth picking up Rick's book, CMYK 2.0. I happened upon it while browsing the stacks at the bookstore and it's a total keeper.

Heck, even if you'll only be dealing with CMYK on an occasional basis, it's probably still worth it.

Unlike a lot of previous tomes about working with four-color, it's both very pragmatic and written from a photographer's perspective.

End unsolicited, uncompensated sales pitch.

P

p_d_f

Participating Frequently

...or make sure there is something of contrasting color in your image - say a bright yellow or orange - and emphasize that as well as the Selective color moves Rick has suggested. Having a contrasting color will make the blue seem bluer than it really is, tricking the limited gamut of press inks into thinking they're more colorful.

A

Anonymous

well said, p_d_f.

What p_d_f is talking about is not really CMYK file prep, but basic color theory. Study the Sistine Chapel, Leonardo, or any of the great Renaissance painters.

A

Anonymous

First, don't waste time comparing the vibrant blue in the RGB file to the converted blue in the CMYK file; it'll just get you depressed. Do your conversion, close the RGB file and work on the CMYK file.

Then, place a color sampler point in the blue area of the image. You'll see that read out in the Info Panel as "#1".

The Info Panel readout will show you the C, M, Y, and K ink values (precentages) of that point in the image.

The most vibrant blue (like a sky blue) in the CMYK color space will be 100% cyan (100C) and about 70% magenta (70M). Any amount of the contaminating colors (in this case, yellow and black) will reduce the vibrancy. Yellow will "dirty" it up, and black will darken it. Of course, a lighter blue will have over-all lower ink percentages. The goal in making blue more vibrant is to reduce the level of the contaminating color(s).

There are many ways to manipulate a color in a CMYK file.

An easy way is to add a Selective Color adjustment layer which allows you to add or subtract ink from a specific color.

Open the Selective Color panel.

Click on the Colors pop-up and choose Blues.

At the bottom of the panel, click the Absolute radio button.

While looking at the #1 readout on the Info Panel, use the sliders to reduce the contaminating color(s).

You should see the effect change on screen in real time.

Note: you'll not remove ALL of the contaminating colors; the goal is to reduce them.

This is the VERY short version of what can be a VERY long story. But it should get you started.

HTH,

Rick

_________________________________

Rick McCleary

author, CMYK 2.0: A Cooperative Workflow for Photographers, Designers, and Printers

Peachpit Press

W

Wade_Zimmerman1

Inspiring

You can make it a bit better using again the adjustment layers

and selection Hue/Saturation where yo can concentrate on the saturation and color shift

without worrying about contrast and brightness.

No matter how adjust it do not expect to see this same result on the printed piece it will be duller.

A

Anonymous

Wade_Zimmerman wrote:
You can make it a bit better using again the adjustment layers
and selection Hue/Saturation where yo can concentrate on the saturation and color shift
without worrying about contrast and brightness.

... or use a Selective Color adjustment layer with blend mode set to Color.

The short story gets longer!

_________________________________

Rick McCleary

author, CMYK 2.0: A Cooperative Workflow for Photographers, Designers, and Printers

Peachpit Press

Tom_Murray_1

Inspiring

Try various adjustment layers. Use the mask to isolate the effects.

Now using Affinity Photo

TwitchOSXAuthor

Participating Frequently

The adjustment layers option helped a little. Thanks.

c.pfaffenbichler

Community Expert

If there is a chance that an image will be reproduced in various CMYK-spaces (say, printed as a poster on a sheet fed press but also in magazines or newspapers) it might be beneficial to maintain the RGB-file and color correct there (with the proper View – Proof Setup/s), then separate from that file according to the various requirements.

Correcting the resulting CMYK-files may naturally still improve the results, though.

As you seem not very familiar with CMYK there’s still the question if the CMYK-profile you use for separating is actually the appropriate one for the specific purpose. If in doubt better ask the print-service-provider.

A

Anonymous

Simple. Don't convert to CMYK and it won't look dull.

CMYK has a smaller color gamut than RGB. Google for "cmyk rgb gamut" for TMI.

M

mnorman2007

Participant

It depends on what the end use is. If it is for print, you will never match the RGB (totally different gamut). Using Pantone matching system, we at least have a final target. Your monitor colors will look brighter ssince viewed in RGB but the final printed copy will be acceptable if you educate your customer on expectations.

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