I'm doing some scans for a customer, he asks what curve settings are for scanning? honestly scan the art and only adjust curve by Photoshop to make them better, but the customer says his curve settings are:

The maximum ink coverage on 4-color: 300%
Highlight dots: 3-5%
Quarter tones: 21-22%
Mid-tones: 44-46%
Shadows: 85%

Ink coverage on 4-color: 300%, it's easy to understand, I really don't know the rest, could someone explain them? thanks a lot.

hl

hl,

What is your customer using the scans for? Where does he get his specs from? Does his work look good in reproduction? Except for the highlights, his numbers favor the light side; and 85% shadows will not appear black in high-quality offset.

Neil

Hi Neil,

Scans are for a book. He got these specs from the printer, what do these percentages mean?

Highlight dots: 3-5%
Quarter tones: 21-22%
Mid-tones: 44-46%
Shadows: 85%

black ink range? or does he ask me to drag down cmyk curve? I really don't understand, I guess he doesn't understand either, he just passes info to me from the printer.

Thanks.

These are percentages you use in Photoshop after you've scanned. There are some scan applications that can apply a curve adjustment in the scan process, a form of automation. But, I'd do it in PS. Now, there is the possibility, based on the original art/photo, final percentages fall within these guidelines ( although highly unlikely ). The numbers themselves tell you how much dot gain the printer is anticipating on-press. If you scan a full color image and open it in PS, you can use the Eyedropper and the Info palette to show you the percentages in the image. You can manually sample the highlight ( lightest area ), qtr. tones, mids, and shadow ( darkest area ). If it is a CMYK image, you'll be able to read the percentages for each process color. Not all of the process colors will need to be adjusted. Often times the Yellow may not need adjusting. Here's a quick overview of their numbers:

Highlight = 3-5%; refers to the lightest area in the image. The printer is trying to avoid "Hotspots"; a percentage of 0%. In my opinion, their press has aged considerably and may be using film to plate where their platemaker cannot image a dot smaller than 3-5%; instead a 3-5% yields a 1-3% highlight.

Quarter / mid tones = 21-46%; these numbers tell how well the press can hold midtones. They are anticipating a 4-6% dot gain in the midtones.

Shadows = 85%; indicates the darkest area of the image. Typically, in a process color image, you'd be interested in Cyan and Black percentages, and the number itself tell you they are anticipating a 15% dot gain in the shadows. This means that your 85% Black will actually end-up at around 93-100%. This is probably the most critical number out of the four. Why? Because if you did not adjust, either in the scan application or Photoshop, and you supplied the printer with an image at 1% Highlts; 25% qtr; 95% shadows; then after dot gain, the final printed image will be a flood at 400+% ink coverage, which means the paper will offset ( be wet stacked and end up sticking and transferring to the other side of the next sheet ), the ink will crack, puddle, and split, and in order to try to control the problem on press, the pressperson will have to cut the fountains back considerably with the final image ending up faded or color casted. And, because they cannot hold a dot of 1-3%, your image highlights will become hotspots.

It also appears they are anticipating a coated sheet ( paper ). By limiting the percentages to around 300-340%, they will be able to control and makeready the press run. Each printer is different, but you should keep your shadows at 85-87%; newer presses may be able to accept 90-93% shadows, but that would depend on what type of paper is being used. Very tricky stuff, but the prepress and press people are letting you know their acceptable parameters using a certain press / paper combination.

Thank you very much John! I'm understanding these percentages.

Usually I scan the original art or photo, then adjust the curves in PS, control highlight area CMYK percentages, 1,1,1,0-5,3,3,0, total ink 3%-11%, shadow area CMYK percentages up to 75,67,67,90, total ink less than 300%, my customers send the fils to printers and no problems.

Should I do the same as I do before? or for example, for shadows: should I drag down the CMYK curve and change the input 100% to output 85% on my adjusted and perfect CMYK images? let's say I have a black square 300% total ink, 85% of 300 is about 260% total ink, after printer's dot gain the black square will be OK or lighter?

Should I still add an extra curve to meet these percentages if I think my scans are perfect?

John,

Thanks for providing the details. I suspect that these are older presses in a film-to-plate workflow. Certainly not the highest quality reproduction.

Neil

No. Do not forget your color settings in Photoshop compensate for dot gain. Adjusting any further than custom curve percentages, such as an overall CMYK shadow adjustment down to 85% is overkill and will weaken color hue, contrast, and brightness. If your scans are coming in at around 300% total ink density, then leave them alone.

Now, who's to say that in some cases you'll want to boost Cyan shadow in order to get bluer mountains, darker sky, or deeper black? Each image is different and should be treated individually. Your friend has given you guidelines on where percentages should fall and I think you've got a good understanding of those numbers. No need to over-do it.