Ron

I know I was a missing something! Thanx to the powerful “Apply Image” I was able to reproduce the graphic and this gave me a much better understanding of what you were explaining!

The graphic is correct. The easiest way to reproduce it (or at least the way I did it when I prepared them): place a duplicate layer on top of the original. If you want, say, to replace the A with a copy of the B, then with the top layer active activate the A channel only, and Image: Apply Image, Souce=name of image; Layer=Background, Channel=b, Blending=Normal, Opacity=100%. You can check Invert if that’s what you’re trying to achieve.

Some images indeed don’t have reference points but the one that you describe may have some. You say you have a black; that should be close to neutral. Yellow flowers are rarely A-negative; if they are it suggests the blue cast that you say you suspect. And greenery should always have the absolute value of the B be at least 1.5 times the absolute value of the A. If not, it suggests the blue cast.

Many suggested color values for common objects are found in the COLOR section of the PPW panel.

Working thru PS Lab Color but having trouble with one issue. I’ve tried to duplicate the versions of Figure 2.4 to better understand how channels work. Unfortunately, using anything other than the original a and b channels does not show what you presented.

I can do a(b) but b(b)is different from the example. Using any of the duplicate channels fails to work. I am sure i am not doing it correctly but can find no way accomplish it. In fact, “a” plus “b copy” looks different from natural “ab”.

Could not find any online instructions on how to create the 16 channel combinations you show.

When we talk about color correction, there are times when there’s no white, gray, or black point.
So, what do we do?

Welcome to the wild and wooly world of CMYK, where we often have to work with incomplete information.

The first questions would be 1) whether you are doing any other CMYK work besides this project; 2) whether these black and whites you speak of are in fact to be printed with black ink only, or whether you intend to use all four inks while emulating the grayscale appearance.

Unless you have done this several times it makes sense to assume that FOGRA39 is the correct profile. If you are not doing any other CMYK work at the same time you can load it as your CMYK workspace under Edit: Color Settings. Then, you can convert your own RGB files into CMYK and they should be more or less correct. If you can’t do it that way, you can convert your RGB into CMYK via Edit: Convert to Profile, specifying FOGRA39 as the destination.

If you have grayscale files and intend to print them with black ink only you are correct that knowing the dot gain is desirable, but there is a workaround that would be effective if not elegant. 1) Make a copy of the grayscale and convert the copy to FOGRA39 (CMYK). 2) Select All and delete to white, meaning that you now have a blank CMYK document that is the same size as the original grayscale. 3) Paste the grayscale document into the black channel of the blank CMYK document. Although this file is theoretically CMYK it should preview and print correctly. Or you can use the slightly more complicated version suggested by Stephen.

If you are intending to print the grayscales with all four inks then converting the grayscale directly to FOGRA39 as above works in principle, and possibly works well enough, but it is not desirable because the black plate would be too light, opening up the possiblity of the picture taking on a distinct color if the job is printed badly. Stephen’s message tells you where to find a profile that will do better.

As you can see Stephen’s message is somewhat more technical and comprehensive than mine. The only thing that may trip you up is that he uses the acronym TVI (tone value increase) which is the term that some use in preference to “dot gain”.

Good luck!

There are many commonly available ICC profiles for Fogra39 – which is also known as ISO Coated v2, both are made from the same characterisation/measurement data. However different profiles deliver different results, usually in the total area coverage and black generation used. If producing 4 colour blacks, then I would use a profile that had a high black generation. In all cases for four colour blacks, I would look for a profile that delivered around 300% total ink (by default this condition uses higher values).

Various profiles can be downloaded from these sources:

I would recommend the following if producing four colour blacks:
coated_FOGRA39_GCR_bas.icc
http://www.colormanagement.org/en/isoprofile.html
http://www.colormanagement.org/en/isoprofile.html#coated_FOGRA39_GCR_bas

The ECI website – ISO Coated v2 300% (ECI):
http://www.eci.org/en/downloads
http://www.eci.org/_media/downloads/icc_profiles_from_eci/eci_offset_2009.zip

The VIGC also offer a suite of profiles using different TAC, two of these here:
http://www.color.org/registry/Coated_Fogra39L_VIGC_300.xalter
http://www.color.org/registry/Coated_Fogra39L_VIGC_260.xalter

Later versions of Photoshop include a profile for “Coated FOGRA39 (ISO 12647-2:2004)”

A grayscale profile using the F39/ISO Coated v2 TVI can be found here:
http://www.colormanagement.org/en/isoprofile.html#ISOcoated_v2_grey1c_bas

And it is also possible to set your Photoshop colour settings to use a CMYK profile K channel in the grayscale working space!

The ICC specs (including both colorimetric and densitometric TVI) for this common printing specification can be viewed here:

http://www.color.org/chardata/FOGRA39.xalter
http://www.color.org/FOGRA39.xalter

The TVI is an integral part of the ICC profile.

So, for four colour work you should not have to worry too much about the TVI. For K only work, you can either use a grey only profile created using the same TVI as F39, or simply load a F39 four colour profile into the grey working space in Photoshop. The only time that you would “need” to know the TVI of F39 was if you were going to build your own greyscale using Photoshop’s Dot Gain or Custom Dot Gain settings.

Of course, you may need to watch your max. K values for detailed shadow areas if this is black only printing.

Regards,

Stephen Marsh

I just grabbed your book Professional Photoshop and I was considering some of your Ledet training. Also in the process of trying out the PPW Panel. I’m great in Photoshop and work in it all day long, but as a designer, not as an official color corrector. I usually leave that to the pros and work alongside them for final output.

Unfortunately, I’ve been tasked with color correcting about 500+ photos myself (BW & Color) BEFORE your class in August. I looked but there doesn’t seem to be any online versions.

Would anyone here know any advice on what dot gain might be used for BWs on a European press using FOGRA39 for the color? Not much to go on, I know. But from my research, it seems like it may be different from the old 20%, especially if its CTP in Shanghai.

I’ve tried asking the print broker as I am in the US, but it seems no one has the answer or really cares to find out. It should be a simple answer to a simple everyday question for a press one would think. The most I’ve been able to get out of them is the ICC profile (FINALLY) and that I’m overthinking it by asking such questions and should just go with the default because everything they’ve gotten back from that press has looked “fine”. Oy vey!