Adobe Photoshop Training with Dan Margulis

I have a couple of questions on working with 5th colour files in Photoshop, that I would really appreciate any help on:

Does anybody know if there is a sound way to calculate the correct 'solidity' for a given Pantone ink when creating a Spot Color Channel in Photoshop, bar the standard explanations of "100% for metallics, 0% for varnishes" etc. ?

I'm also curious about the typical printing order of ink which is presumed in Photoshop CMYK files, is it C,M,Y and then K ?

If you add an extra color to a job, does it presume that the 5th Color is the last ink down on press and build its overprint previews of the color on that basis ?

many thanks

___________________________________________________________________________

The solidity can be whatever you want it to be. It's just a way for you to preview the result of the 5th color mixing with the 4 color. It has no effect on the final output. I personally like a low solidity so I can see more of what's going on.

If you add an extra color to a job, Photoshop presumes that you want the same solidity you had last time for the preview.

___________________________________________________________________________

In addition - one must manually create any knockouts in the other plates and or spreads/chokes in the other plates or the spot channel, as spot channels in Photoshop overprint by default - unlike illustration and layout which automatically knockout underlying elements (object orientated art and PostScript presumes knockouts).

The solidity preview would obviously not apply in these areas, as the spot ink is directly contacting the substrate.

Stephen Marsh.

___________________________________________________________________________

The built-in Photoshop engine doesn't assume anything, it just treats the inks as all 100% transparent so that the order wouldn't matter. In reality, of course, it does matter.

Nowadays the typical print order is KCMY, but there are still a number of printers who use YCMK, which used to be more popular than it is today. Some other variants exist.

Dan Margulis

___________________________________________________________________________

The most accepted sequence is KCMY (Black can be first or last). if you print with the MCY sequence the reds will suffer. (from Kelvin Tritton's book on color lithography) Green suffers in the CMY sequence but not as bad as Red does in the MCY order. The reason for the old YMCK sequence was that the yellow (in the early years) was opaque and had to be printed first.

Dan

Dan Remaley

Process Control Mgr.

Graphic Arts Technical Foundation

412.741.6860x450

___________________________________________________________________________

Many thanks to all you all confirming my worst fears !. It would seem that if the ink rotation sequence for CMYK work can have an impact on the color produced then I can hardly expect to rely upon a 'solidity' box to demonstrate an accurate preview of another ink being used. Right ?

___________________________________________________________________________

On Jan 23, 2004, at 3:00 PM, simo_bogdanovic wrote:

They're two different issues. A profile will produce the necessary separation which takes the effect of print sequence into account, and once assigned to an existing CMYK image will also provide for an accurate soft and hard proof.

Spot color solidity is Adobe's way of telling Photoshop how opaque, or translucent, ink is. For whatever reason, Pantone and Adobe have not released solidity suggestions for various Pantone colors. The setting only affects preview, but if you could better trust the preview accuracy then surely it would then affect your design. So what's needed is a good solidity setting, and as far as I know that information is not documented anywhere except in the brains of people who are skilled with spot color printing and care about giving Photoshop correct solidity settings.

Chris Murphy

Color Remedies (TM)

www.colorremedies.com/realworldcolor

___________________________________________________________________________

Simo writes,

Right.

Using a fifth ink in the middle of a CMYK picture is not a sport for the timid. We have printed so many trillions of CMYK images that we have a reasonably good, although not perfect, idea of what happens. Throw in a dark green ink or some other weird color, and you're dealing with all kinds of unknown dot gains, transparency factors, laydown order issues, and screen angle difficulties. Plus, our ways of proofing are very primitive short of actually putting the job on press for a trial run.

Therefore, good results are going to depend on being conservative and using the fifth ink only in areas where it's really needed to accent the color. That way, it puts a lot of control in the hands of the pressman, who can increase or decrease the fifth ink without wrecking the rest of the image.

Dan Margulis

___________________________________________________________________________

What further complicates the matter is that Photoshop always treats the spot ink as printing on top of the CMYK, in terms of press ink laydown. So a metallic ink, for example, which is very opaque, would normally go down first on press. Since Photoshop forces the metallic to go down last you cannot set the opacity to solid. You must pretend it is transparent.

___________________________________________________________________________

Order of inks (metallic then CMYK?) requires you to speak with your printer and then to work out your project based on what they say, and lastly to make sure they stick to what they told you. My last metallic job, the printer said they would put it down first. The press crew then ran the metallic last.

Their reasoning had something to do with how "waxy" the metallic inks are and that CMYK wouldn't trap well onto it. So they put the opaque ink on top, wiping out all detail. Tra-la. They got great coverage on all 5 inks, but they (the press crew) didn't consider opacity.

I think if the job is a solid block of metallic that knocks out CMYK, then a press crew would be likely to put it down first. In a 5-color photoshop file, they might want to have it last. And it's not unthinkable that they would have 4 units of their press already loaded with CMYK and a less-used 5th unit, probably at the end, would get the spot color regardless of the nature of the job.

___________________________________________________________________________

The harsh reality of printing with metallics is that the laydown order has to change AND the tack of the next ink (usually black) will need to be reduced in order to chemically trap to the metallic ink. The extra cost for making these changes should be figured into the bid. If simply left up to the pressman, he will usually take the easy way out and ruin the job. Best to closely monitor these details if you are the separator or customer.