How to use Rich Black

[achasin]

I had originally posted this in the InDesign forum, but someone over there suggested I try here instead.

I'm currently working on printing a zine containing some of my black and white photographs.  I printed a test zine with the printing company I'm working with and the images look dull and flat - no deep blacks to speak of.  The zine was printed on a digital press and I used the CMYK color profile provided by the printing company (Coated GRACoL 2006 (ISO 12647-2:2004)) in my images/InDesign file. 

To remedy the lack of deep blacks, the printer suggested that I use Rich Black (CMYK = 30% 30% 30% 100%) rather than Standard Black.  I understand how to create a Rich Black swatch in InDesign and apply it to something like a solid black background, but I don't really understand how to apply that swatch to my photographs.  

Can anyone suggest how I might go about using the suggested Rich Black to produce deep blacks in my printed photos, using InDesign and/or Photoshop?  Is this something I need to do manually in every black and white photograph (currently in TIFF form) that will appear in my zine?  If so, how do I go about doing this in Photoshop in the most efficient way?

Thanks in advance.

[D Fosse]

Are these photos grayscale (single channel)?

This will output from InDesign on the black plate in whatever CMYK profile is appropriate for the printing process. This is K-only black, 0-0-0-K.

The problem with that is that black ink has rather low density, resulting in flat images lacking "punch".

Rich black uses all four plates to produce a much deeper black. CMYK profiles have a built-in total ink limit. If you exceed that ink limit, you get smearing and drying problems. So converting from RGB goes up to that limit but does not exceed it.

Long story short - if this is printed with a CMYK process, the simplest way is to get the correct CMYK profile, and convert directly from monochrome RGB originals to CMYK. Then you get the deepest possible blacks.

However, using all four plates involves a certain risk of color cast if there are any inaccuracies in the process. @Stephen Marsh  or @c.pfaffenbichler may have some tricks to avoid that.

[achasin]

My original files are in RGB format.  The printer requires the PDF to be in CMYK using their supplied color profile.  I did take those RGB files and convert them to the CMYK profile before bringing them into InDesign.  I then exported the InDesign file to a PDF using the same color profile and made the PDF file available to the printer.  However, the hard proof I received looks much more washed out than things looked in InDesign.  The printer suggesting using Rich Black to overcome this issue, which is what led me to my original question of how to do that.

One thing I did notice is that when I Proof Colors of the CMYK images in Photoshop, the blacks look much more grey than when not proofing - despite the fact that my Proof Setup shows that the Device To Simulate has the same color profile as the image being proofed.  I may be misunderstanding how color proofing works, but I would expect no change when I proof an image with the same color profile as the simulated output device.

[Stephen Marsh]

@D Fosse – thanks for the shoutout, yes I do have something to add to the discussion!

A special GRACoL 2006 profile using strong GCR:

https://www.colormanagement.org/en/gracolprofile.html

EDIT: As this is a digital press, this may or may not have any noticeable benefit, as the input colour will be transformed into the final press colour space, so this is very different to traditional output... And even with traditional output, there may be a colour transform before final output anyway, changing the input values.

Does the print service provider accept RGB input? Depending on their RIP/DFE setup, you may get better results with neutral RGB files which will be transformed into the final press colour space.

[c.pfaffenbichler]

If a strong-GCR-variant of the profile is available that seems like the best approach, so kudos to @Stephen Marsh for locating it. 

Assigning a rich black to a grayscale image is risky because, while it may not exceed the TAC, it does not honor the »gray balance«, so certain ranges of a gradient might assume an unintended hue. (Unfortunately variability during a print run may cause tone-y grays even in a properly separated image.) 

In the market where I am active rich black generally features a stronger cyan (like 50/40/40/100) because equal amounts of the three non-neutral colors usually come out a little beige. 

[achasin]

The printer does accept RGB input, but they recommend converting to their color profile yourself so you have complete control over the process.

[Stephen Marsh]

Are you supplying an InDesign package, or a PDF?

Are the images in InDesign RGB or CMYK? If CMYK, do you have the RGB originals?

Do the original images have a full tonal range and appropriate contrast before going to print?

Is the paper gloss, semi-gloss or matte/uncoated?

[achasin]

Hi Stephen, thanks for responding.

I'm supplying the printer with a PDF.

I have the RGB originals.  I produced them from scans of black and white film negatives.  I converted the images to the printer's CMYK color profile before importing them to InDesign but I have the originals to start with if I need to start from scratch.

Looking at the black/white points in Photoshop, I think the originals do have a full tonal range.

The paper I've chosen is what the printer calls 'satin' - probably semi-gloss in your terms, although it's not very glossy.  It is not uncoated.

[Stephen Marsh]

I'm supplying the printer with a PDF.

By @achasin

Then you don't need to convert every image to CMYK, you can just link the RGB versions and then convert to CMYK at PDF output. The only reason why you would link to CMYK versions is that you may need to create custom edits beyond the default profile conversion (watching out for total ink and gray balance) or convert different images using different profile variations for the same GRACoL 2006 print condition, which is all pretty advanced stuff and not for the majority of users.

https://creativepro.com/import-rgb-images-indesign-convert-cmyk-export/

Looking at the black/white points in Photoshop, I think the originals do have a full tonal range.

The paper I've chosen is what the printer calls 'satin' - probably semi-gloss in your terms, although it's not very glossy.  It is not uncoated.

OK, keeping in mind that CMYK on satin/semi-gloss has a lower dynamic range, one often needs to exaggerate the contrast a bit more if the dmax is correct.

One "old school method" is to ensure that the tonal range of interest in the image has a steeper curve to add more contrast to the key area, sacrificing other areas of lesser interest.

If you don't have time to treat each image or certain key "hero" images on a case-by-case basis, then you may wish to look at automated overall adjustments that can be batched to enhance the contrast of all the images with the same fixed setting.

[achasin]

Thanks for the suggestion.  I'm not in a hurry for this so I will take the time to make some adjustments to exaggerate the contrast in the hopes of getting a wider dynamic range on the satin paper.

[achasin]

Quick question:  Based on your response, I realize now that I don't need to convert my RGB files to CMYK if I'm going to export my PDF to CMYK, but is there any harm in doing so?  Will the result of printing from the generated PDF be the same?

Your suggestion to somewhat exaggerate the contrast is one I'm going to try.  If I do that, I'm wondering if my next test print with the printer should again use Grayscale rather than printing in color using Rich Black.  My concern with printing the zine in color is the possibility of color casts - not something I want, especially if the black point isn't going to be improved.

[jane-e]

I had originally posted this in the InDesign forum, but someone over there suggested I try here instead.

By @achasin

See also the answers from @rob day in the InDesign forum.

https://community.adobe.com/t5/indesign-discussions/rich-black-for-black-and-white-photographic-imag...

Jane

[Stephen Marsh]

Thanks Jane!

That post from @rob day is great.

I prefer using the standard GCR profile conversion than assigning a rich black swatch to the grayscale image in InDesign, here is a layered example comparing the standard profile conversion against the same dmax value and the print service providers suggested dmax.

[rob day]

Hi @Stephen Marsh , without seeing @achasin press sheet we can’t know for sure, but it sounds like the printer isn‘t allowing the PDF’s CMYK values to output—there is an additional conversion happening in the driver or RIP.

I think this is a common problem with composite "digital" printers. The printer apparently is asking @achasin to make a conversion to Coated GRACoL, and then from InDesign, Export a PDF with No Conversion and no profiles—using their preset all color is exporting as DeviceCMYK or DeviceRGB.

That would be OK if they were actually printing the DeviceCMYK values with no additional conversions, but it’s hard to believe a black like 86|75|69|94 would appear washed out. You could make a different separation and get a different dmax value, but I don’t see how that would help if the provided CMYK values are not making it to press.

[Stephen Marsh]

@rob day – Thanks for the reply.

When somebody mentions neutral grey images in CMYK, my reflex response is to think GCR!

As I wrote in a subsequent post, for digital output the press colour space is going to be used, so in theory it shouldn't make much difference if the standard or GCR version of GRACoL 2006 is used, as the input CMYK values will be converted to the final digital press space.

So I agree with you about the additional conversion.

The print service provider's suggestion of applying a swatch of 30cmy100k to the grayscale images would likely lead to an even more washed-out result than the standard or GCR profile results.

I still think that providing RGB data would be best if the PSP allows this.

[achasin]

Thanks, yes, I've been conversing with @rob day in that thread.  Unfortunately, we've had no power for three days due to the recent storm in California.  Hoping to have power restored today and then I'll get back to these threads.  Thanks to everyone who continues to respond.  I appreciate all of the help.  

[didiermazier]

Each country printing industry has its own standards so this answer is nothing but the way I worked for french magazines :

You cannot be over 300% total ink percentage. They say it would be "buttering" the plates…

So I used for setting black point :

K: 85

C : 60

M : 50

M : 50

The total is 245% ink and works great. Note that there is a little more blue (+10%) tha for Y and M to add contrast

For the white point :

K: 0

C : 3

M : 2

M : 2

This allow not "making a hole in the paper" as my guys use to say…

Except of course for very specular light (i.e. the very very white in the center of a bulb lamp…)

Again this is just a personnel professional experience, but i hope it will give hints…

[D Fosse]

Yes, and this is why the ink limit is built into every CMYK profile (known as TAC, Total Area Coverage). For coated paper profiles this is in most cases around 300%. If you convert from RGB, it will not exceed TAC.

Cyan ink has lower density than magenta and yellow, so the percentage is higher for a neutral result. You can see this if you "desaturate" a CMYK file, averaging out the numbers - then the result is a brownish image.