Low % warning

[Lukas Engqvist]

It happened again. An almost white background in the press as a visible square, I am sure I am not alone.

We had the annual report printed by a digital printer to proof but we know that the 0-2% is less visible on the indigo. I know some people use clipping to prevent this happening, and yes it was there on the raster data, to fix it at preflight wouldn't have been a problem, but I'm thinking wouldn't it be good to have a low% warning in photoshop, InDesign and Acrobat. Like we warn for ink limit, some tool to help us heads up on risk files.

I know it would be virtually impossible to preflight since we want the smal % for when we have shadows fading to white, I'm just starting to think, but mybe some one has thought this before me?

 

[mattbeals]

I built a preflight check for this with Callas pdfToolbox for a customer. We check raster and vector objects.

 

[Lukas Engqvist]

but really would be good to catch before pdf, best in photoshop. Especially when making transparent backgrounds, ie masks.

 

[DavidMa]

too bad most apps don't read anything less than 1% (like Photoshop), so I doubt that you could get a preflight app to spot it.

 

[mattbeals]

You want to preflight for less than 1% coverage in a given area? Send me a sample, I'm curious to see if we can.

 

[Lukas Engqvist]

too bad most apps don't read anything less than 1% (like Photoshop), so I doubt that you could get a preflight app to spot it.

What do you mean don't read less than 1% if you have 256 levels you are less than 1% if you have level one or two. Usually it is noise however so you would find a couple % in background. But in a way you are right there are limitations in Photoshop, but if we don't make a noise nothing will ever change.

(though it doesn't solve the problem, infact i think it is a worse option:
In quark there used to be a threshhold clip set at 3 or 4% i think was the default.
Also in the rip it is possible to clip, or design a linearisation curve that clips. )

The problem is when you want to have smooth shadows/fades to paper in some parts, but you don't want to have bad masks, poor cut-outs showing. It's a little like transparency issue, you don't necessarily need to do anything about it but there isn't the time to check if everything is a potential problem, but you want the heads up where text is rasterised etc.

 

[marc3llo]

Hi Lukas,

you can put an adjustment layer on top with the curve all the way from left to right (or right to left, depending how you have your settings), so, if you have only 1% in your file, with the layer adjustment visible, will be 100% and then you realize.
I know you want like a plug in or tool, but this adjustment layer works really great.

hope it helps
Marcelo

 

[Stephen Marsh]

but really would be good to catch before pdf, best in photoshop. Especially when making transparent backgrounds, ie masks.

I have attached an action that uses a threshold adjustment layer set to 255. This is only a proof of concept action, one may need to adjust the threshold value or other options as needed.

Using the Script Events Manager, one can bind this action to the save command if this was a necessary check on every image - or one could simply bind it to an F-key and remember to manually use the action when working on transparent background images etc.

The action cleans up after itself.

I am not saying that this is the ideal solution, just a solution!

Stephen Marsh

 

[disbellj]

Lukas,

Sounds like maybe someone converted to CMYK using Absolute Colorimetric Intent. Other than that, it's usually bad clipping/retouching where someone tried to remove the background and wasn't fully successful.

Regards,

Don

It happened again. An almost white background in the press as a visible square, I am sure I am not alone.

We had the annual report printed by a digital printer to proof but we know that the 0-2% is less visible on the indigo. I know some people use clipping to prevent this happening, and yes it was there on the raster data, to fix it at preflight wouldn't have been a problem, but I'm thinking wouldn't it be good to have a low% warning in photoshop, InDesign and Acrobat. Like we warn for ink limit, some tool to help us heads up on risk files.

I know it would be virtually impossible to preflight since we want the smal % for when we have shadows fading to white, I'm just starting to think, but mybe some one has thought this before me?

 

[Lukas Engqvist]

Thank you for your input.

And disbellj, no there are buggs/limitations in some CMM's and one of the most common ones is the inability to keep white white. We first ran into this with our OPI server (Full Press).

 

[DavidMa]

What do you mean don't read less than 1% if you have 256 levels you are less than 1% if you have level one or two.

You will not be able to detect anything less than 1% with an onscreen densitometer in most apps.
The only way to view this is to bump up the image with curves and to get rid of it you would need to use a curve to eliminate any thing below your threshold (whatever you don't want to print). You are essentially "flying blind" because you can't see it onscreen without adjustments to the image.
The only app I've seen that can read that small of a percentage in an image onscreen is Esko's Packedge and Colortone.

...but I could be wrong.

 

[Lukas Engqvist]

Well that is exactly why it ought to be as a tool the same way that we have gamut warning

 

[marc3llo]

Lukas,

are you deleting the white background with the "delete" key? Because I know that in some Mac's if you delete in Photoshop with the key, in order to erase the background, keeps 1% of colour in the image.. it sounds weird, but it is true. Used to happen to us, since then we delete/erase with the curves. Only happen in Mac and not all of them, we were using G5.

hope it helps.
Marcelo

 

[Lukas Engqvist]

thank you for your suggestion Marcelo, but the problem is specifically with preflighting "press-ready" files.
If I make the stuff myself I know how to make sure it doesn't happen.
The 1% you get when deleting, nah don't believe you, could possibly be that you have an almost white as background, or the RGB problem mentioned earlier with the Apple CMM, wich would explain why you have experienced this exclusively on the Mac.

 

[marc3llo]

Yes, I know it sounds odd but, may be you are right and is something regarding the Apple CMM. I am 100% sure that is not 1% of color in the foreground or background.. so, must be what you said.

Anyway, to solve this problems I just have a look at "View X" in Packedge, but it can be done also with a set of curves. I mean, you can even create an action and that will be the tool you want. But you already know that!

 

[disbellj]

Why not just "etch" everything on plate: 1% input to 0% output, smoothing the rest of the data? Would you really be able to tell a "sharp edge" doing this? I wouldn't think so. Just my 2 cents, since it looks like this is a repeating problem for you.

Regards,

Don