highlight tints_invisible till printed

[frailer]

Not sure what thread this fits in, but it's proving to be a regular PITA. Designer has, say, group shot in colour against white background. The intended effect is to have a soft deep etch of the heads against a white page.
The deep etch in fact has blotches of CMY over the heads, (against the "wall" if you like). These are in the 1-3% range when measured with the eyedropper, But CANNOT be detected, even on zoom-in, on screen. (Pretty good Sony OEM'd 21" monitor).
We can often pick it up on negative film and opaque it out, but that's only "finger in the dyke" stuff. The real problem is that our Black Magic/ EPSON 7600 struggles to represent that level of highlight tint. Stock is Mitsubishi Imperial 180 gsm through the EPSON. I'm about to arrange a press calibration, as well as a filmsetter calibration, (they're both due anyway). This should rule out anything out of whack there, although I think they're within range.
Have also heard that this is one problematic area for digital proofing in the CTP era. Ugly, blotchy vignettes which have come out of PhSh, rather than Illy, also seem to pose problems.
Apologies for the long-winded description, but is anyone else experiencing this? I've heard mention that on CTP, the dot retention makes this sort of thing worse than on film.

[GGraham]

Frailer,
This is not a pre-press problem. What would your “Hotshots” designers do if you failed to hold all the 1 to 3% dots in the skin tones? People have read the color by the numbers. Nobody can see a 1% tint on the screen.
ggraham

[TimS]

Checking for this is standard procedure on those types of images. The standard fix: use the magic wand in photoshop with a small tolerance to select the white areas (use contiguous to stay in the white area). Apply a small feather. Expand the selection as needed to get close to the heads. May have to use a bit of lasso to get some extra bits. Hit delete. Result should be unnoticeable.

[mc_hristel]

Another "fix" that I use is to go under image> adjustments> levels, and using the white eyedropper, click on the white background. The color values are then shifted to make this 0% CMYK(if you are 1-3% off, that is how much shift you would see). Be careful, because everything will be changed unless you have only the problem white background selected.

-MC

[frailer]

Your answers seem to me to be in the right direction. need to get my PhSh skills up anyway. May not be able to get to hack this file as an exercise until next week. Shall let you know how it went. What I do know is that these sorts of problems are about the only really testing stuff we're facing at the moment. Am convinced that half-witted digital photography and then inapproprite PhSh work are to blame. Thanks for the tip

[TimS]

I think it is also due to the fact that evereone is busily jpegging everything these days. jpeg rounds off the math as part of the compression process, that's why it is callled a lossy compression (as opposed to lossless compression when you make a .sit or .zip file). As a result, what was once a stray pixel because a little group of pixels, and then you end up with the little smudges in the white areas you are seeing.

Perhaps ask your client not to jpeg files, but they will of course think you are completely insane as they know it all already. Try it yourself to see, put a little process pixel in a white area, jpeg your file with lots of compression, and open it up and you'll see what I mean.

[frailer]

Finally got to revisit this as a post facto exercise. Done the Magic Wand thing; tolerance adjustment etc. Is there a way of "adjusting" the Wand deep etch with the Pen Tool? Combining the 2 somehow? Then be able to hit delete? I'll get out the PhSh VTC disk out tonight, but would be glad of of any brief input. Playing with this stuff whets the appetite; just not enough time.
The complicating factor on this is that there is a horizontal "double-vignetted" (top and bottom) band of 4 col. grey at about 7% running behind the group shot. Can't see it as a layer, so it's in the shot as a background, I guess. I got into Image Info and it was shot with a 16+ MegaPixel Canon ($8,000+), but the subsequent PhSh work I suspect is the problem. The skin tones etc. are great, definition/balance good. Can't attach image due to the public nature of the image/privacy etc. Though I would love to. File is a TIFF, so can't blame file format. Could attach a screenshot of Image Info, but would someone tell me how to do this; (simple, I'll bet). Camera data2 says Pixel dimension about 5000x4000. res=300x300.
Cheers

[tlotzer]

To see these type of edges easily, I will make a new curve adjustment layer, drag the 100% all the way left to around the 12-15% point. This will wig-out your photo, but since it's on an ajustment layer, it can be turned off/on or deleted when done.

The "wigged-out" curve will now show you where those pesky 1% edges are hiding.

We have heck with harsh shadows that drop off at the 1% on press.

[frailer]

I see where you're going in theory, but my prac skills are still cranking up. Shall certainly hack into it. Good thing is , this is now a learning exercise for me; but won't have time to re-visit it till Fri arvo+. Might be fishing for the odd pointer past then. Interesting to know others having similar problem, (what makes us so special anyway?).
Thanks