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Author Topic: Print black density  (Read 1433 times)

LGeb

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Print black density
« on: January 06, 2016, 09:08:38 pm »

If different printers, inks and papers all can produce different max densities how is an image file mapped to the maximum density of the print? For example I may print an image on my 3880 with matte paper and 0,0,0 will give me a density of about 1.7. Print the same image with a fiber paper and photo black ink and it's about 2.1 or 2.2. The new P800 prints the same black at a DMax of 2.6. That's 3 stops denser than the matte paper and 1.5 stops denser than the old printer could do.

It's obviously not just the max blacks that got denser on the new printer, though the midtones and the highlights look the same. I don't think it's as simple as every tone got 20% darker (or some other number), but I haven't taken the time to print out equal patches (and my 3880 can only print on matte now, so it's a hard test to do) and compare the readings. Can anyone explain how printer profiles handle differing maximum blacks?

Is there something obvious I'm missing to accommodate the differences? Or will I need to adjust some of my previously worked images to print on the new printer, assuming I want them to have the same density?
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Doug Gray

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Re: Print black density
« Reply #1 on: January 06, 2016, 09:41:06 pm »

If different printers, inks and papers all can produce different max densities how is an image file mapped to the maximum density of the print? For example I may print an image on my 3880 with matte paper and 0,0,0 will give me a density of about 1.7. Print the same image with a fiber paper and photo black ink and it's about 2.1 or 2.2. The new P800 prints the same black at a DMax of 2.6. That's 3 stops denser than the matte paper and 1.5 stops denser than the old printer could do.

It's obviously not just the max blacks that got denser on the new printer, though the midtones and the highlights look the same. I don't think it's as simple as every tone got 20% darker (or some other number), but I haven't taken the time to print out equal patches (and my 3880 can only print on matte now, so it's a hard test to do) and compare the readings. Can anyone explain how printer profiles handle differing maximum blacks?

Is there something obvious I'm missing to accommodate the differences? Or will I need to adjust some of my previously worked images to print on the new printer, assuming I want them to have the same density?

This is called "black point correction/compensation." This is the Adobe document that describes how they do it.
http://www.color.org/AdobeBPC.pdf

Generally, if you print Perceptual Intent the profile itself will implement something similar to this. It maps L=0 to one end of the printable range and L=100 to the other, which is the paper's white point.

If you print using Relative Intent the upper end, L=100, is scaled to the paper's white point but the lower end is not. It just goes down to the paper's blackest color then stops there. So darker areas are blocked. OTOH, if you also check the BPC box, it will implement BPC per the Adobe paper linked above.

Note  that some canned profiles incorrectly implement BPC in the Relative Intent tables. This messes up the accuracy of soft proofing which depend on the profiles to accurately reflect the colors that can be printed.
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LGeb

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Re: Print black density
« Reply #2 on: January 07, 2016, 08:04:23 am »

Doug, thanks for pointing me in the right direction. I've mostly ignored the rendering intents and had forgotten about the black point compensation option.
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GrahamBy

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Re: Print black density
« Reply #3 on: January 10, 2016, 03:54:35 pm »

What intriques me though is how this works for the Epson ABW and Canon monochrome printer options: the Canon one at least greys out the choice of ICC profile and the rendering intent (I think Epson does the same), so the driver is doing this scaling purely based on the paper-type specification. On RC papers it doesn't seem to matter, so far as I can see from printing a 128-step ramp... and they are all I use. However with the much smaller Dmax of matte papers, it must get pretty hit & miss.
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hugowolf

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Re: Print black density
« Reply #4 on: January 13, 2016, 12:07:31 am »

Running under recent versions of OS X, the ability to use ICC profiles and ABW was removed, but under Windows, at least up to Win 7, that is still an option. You are effictively double profiling, but you know that when you make the profile. And ABW gives a better Dmax.

Brian A
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