# Editing photos for CMYK printing

This question is a follow-up on this earlier question here

As I am attempting on printing a photo-magazine in black and white, I am losing rich blacks in my photos when converting them to CMYK and previewing the tones with "Proof Colours" in InDesign.

As mentioned in the answer left by Scott, CMYK won't appear as black as RGB blacks viewed on a monitor. He also mentions how a proof print would be a much more accurate representation of what the preview in ID shows.

Still, I do fancy a bit of certainty or control, so I went into Photoshop to play with the photos a little. When converting the photo to a CMYK colour profile, I saw no change unlike in InDesign.
I used the colour picker to see the CMYK values for some of the darkest blacks in the photo. These were approx. 90, 80, 60, and 100 respectively. This is in total much more than the 300% which I have been told would give drying issues, and thus smudges.

Are these values accurate? Should I lower these blacks, even though the photo previewed in ID already seems quite dull?

• You can't put that much ink even on kitchen roll in one pass. It would be the equivalent of 2 tablespoons of honey on each of 18 slices of toast. You'd end up with a block of paper. [Modern systems may be smarter, but I worked on a standard offset litho press for many years] Black on paper is seen by your average human as 'black'. They don't get the microscope out to test its density. – Tetsujin Jul 16 '19 at 18:02
• Kitchen roll is probably a bad analogy - too frail even if it is massively absorbent. – Tetsujin Jul 16 '19 at 18:05
• @Tetsujin so, you're suggesting I tone down the blacks? – Tim Stack Jul 16 '19 at 18:17
• Note that in photos the perception of "black" is greatly altered by surrounding grey/white portions. In most instances a rich black of 40C20M20Y100K is sufficient. If you want "vantablack" you'll have to do some digging, for both a provider willing to try and probably your pockets for more cash. :) Because no one here can see what you see.. all we can do is guess. 90/80/60/100 (330%) is past most ink limits (300-320%) the 70/50/40/100 you had before was fine at 250%. – Scott Jul 16 '19 at 22:56
• Really, the only way to answer what you are asking it to speak with a print provider about their capabilities. Every print provider will have their own rich black breakdown based upon their specific equipment and environment. Note that in some cases you may be able to do a "double hit" of the black plate to darken things a bit more.. but again.. cost may be a factor. That makes it a 5 color job. And it all requires a conversation with the print provider. – Scott Jul 16 '19 at 22:58

Doing my best to formulate a helpful answer based upon comment discussions.....

This can often be a matter where people struggle. Sometimes what you see on screen simply isn't going to match what comes off a press. So you learn, through experience, that "trusting the numbers" at times is the best you can do.

Monitors or screens, all of then, use RGB to convey color. So, things like "print proof" or CMYK images on screen are actually "best approximations" using an RGB color device. They are never going to be 100%, dead-on, always-accurate in visual appearance.

A properly calibrated screen will do a much, much better job at approximating what a CMYK color may look like. But even the best calibration will have a margin of error depending upon specific colors. This is merely something one must overcome when working digitally for CMYK reproduction. It's still far better than the old days where you say separations and had to "trust the numbers" because there was no "preview".

For example... if you know the red you want is 10/100/80/20 but it looks dull and washed out on screen.. then you need to trust that if it's set as 10/100/80/20 it will print as you anticipate even if your monitor doesn't show the color as you expect.

If a print provider has supplied a color profile to use, or has provided a breakout for Rich Black values, then you should be confident that the profile and those numbers will result in a good quality print from that provider.

Every print shop is different and they will all have their own values for Rich Black. The numbers you are given are based upon their environment and what they have determined gives their customers the best quality. No print provider wants to have work rejected or rerun. It is generally in their interest to give you the best they can give. So, you should trust that, if you were given color breakouts they will result in quality from that print provider.

If one simply can't get past what is seen on screen. You can possibly run a "test print" or get a chroma key done to test values.

To test something like rich blacks, you could set up a test with varying back values like so...

Have a chroma key created of that test and you can then physically see what is going to be reproduced on press. However, I'd stress again, if a print provider has supplied a profile and rich black value, you really should stick to those.

If a provider has not provided such things, ask them! Many will me absolutely thrilled to supply a profile or rich black values.

The long answer: I do not get it... I am totally confused by your question. Let's see.

As I am attempting on printing a photo-magazine in black and white.

So, just use one ink. Black. If you really want deep black, you should ask the provider to use a deep black ink. In very rare occasions, you can ask the printer to pass twice each paper with the exact same plate and alignment. This will give you a deep black k200. Yeap it sounds weird, but it works. The point is that the printer (and you) needs to be willing to experiment.

I am losing rich blacks in my photos when converting them to CMYK

Did you want black and white or not?

CMYK won't appear as black as RGB blacks viewed on a monitor.

You should have 1) Your monitor calibrated and 2) The CMYK simulation turned on even if you are working on RGB.

He also mentions how a proof print would be a much more accurate representation of what the preview in ID shows.

Depends on if the proof is really a proof and not only a simple print. This should be (the same as your monitor) calibrated. Did I mention the word calibrated?

Still, I do fancy a bit of certainty or control, so I went into Photoshop to play with the photos a little.

If you do not know what are you doing, do not play with a CMYK file. Do whatever on an RGB one, but leave the CMYK alone.

When converting the photo to a CMYK color profile

Ok. You did work on the RGB file. Good.

You do not convert a RGB photo to "a CMYK profile" you convert a photo on RGB model to CMYK model using a specific color profile.

If you choose your color profile correctly you do not need to worry. Leave the program do the conversion.

Darkest blacks in the photo. These were approx. 90, 80, 60, and 100 respectively.

Ouch... something is not right here.

There are some color profiles that use 330% TAC (Total ink) this is the case of Fogra 39... do you need Fogra 39? If your provider is really ok with the TAC, go ahead.

But I am wondering if you are just rounding numbers (c91 m79 y62 k98) or tweaking the file.

Modern printers can use Fogra39, new inks, additives, special drying systems, conditioned and humidity controlled air and environment. But if your printer does not use it try to stick with a color profile that stays on the 300% TAC. Ask them.

This is in total much more than the 300% which I have been told would give drying issues, and thus smudges.

Depends on the printer.

Are these values accurate?

They are not, I wrote the accurate value above)

Should I lower these blacks, even though the photo previewed in ID already seems quite dull?

No. If you want (or need) lower values, use a different color profile.

An image well prepared, well printed on a good paper using a 300% TAC will look very good. The 330% is just a bit deeper, but only if you put them side by side. A normal user will not say. "Oh, this photo of the universe is dull, they should have used more TAC".

If you want to punch the colors a bit, try to use a varnish.

Remember that color profiles are for specific combinations of paper, inks, and printing. But the main factor is the paper.

The 300% and beyond TAC is for coated paper. There are some papers that use even less TAC, like 220 ish, so. Ask the printer.

The short version... Use another color profile. Not Fogra 39.

• A lot to go through here, can't comment on it all. The short comment: my lab requests me to use Fogra 39. The colour values from the image came from PS and were indeed rounded. You mention only K ink should he used, but what decided this will actually happen to my photos? As I sample values in PS, they contain CMY values too. It's all very puzzling, this printing. – Tim Stack Jul 25 '19 at 5:46
• If your print is really black and white, just convert them to grayscale. – Rafael Jul 25 '19 at 15:15