What changes do you usually make when Softproofing?

[MarkM]

On the other hand, what else can out-of-gamut be, other than colors that want to push channels above 255 or below 0? If a color can be expressed as an RGB triplet in any given space, then that's what that color is. It has to be in gamut.

I think this is correct with the single caveat that you can't distinguish between numbers that are clipped to 255 or 0 and those that legitimately are 255 and 0 without clipping.

[bjanes]

Well the OOG overlay doesn't work that way, at least as I see it. I've got a black to white 21 step ramp in Adobe RGB (1998), if I soft proof for sRGB and ask to see the overlay, none of this is shown as OOG. That's why I asked about your targeting of black with the eyedropper, if it represents "colors" that clip. That's my concern, and it appears the current OOG overlay doesn't target those true blacks or true whites for one.

Why should there be OOG when softproofing gray scale images between Adobe RGB and sRGB as the gamuts from L*a*b 0,0,0 to 100, 0, 0 are the same, as far as I know. In a Colorthink plot, there is a straight line extending from L*a*b 100, 0, 0 to 0, 0, 0. In other words, their gamuts with regard to luminance are the same. Their gamuts diverge when chroma is involved and a and b diverge from zero. Isn't this the case?

Regards,

Bill

[digitaldog]

Why should there be OOG when softproofing gray scale images between Adobe RGB and sRGB as the gamuts from L*a*b 0,0,0 to 100, 0, 0 are the same, as far as I know.

That's why I asked the question. Photoshop doesn't show any OOG overlay, using the technique to pick via an color channel as described earlier does.

These are not grayscale images but rather a grayscale channel of a color image. That said, I think what Mark wrote in his last reply might indicate this process isn't selecting just OOG colors which might make it's selection process an issue.

[bjanes]

That's why I asked the question. Photoshop doesn't show any OOG overlay, using the technique to pick via an color channel as described earlier does.

These are not grayscale images but rather a grayscale channel of a color image. That said, I think what Mark wrote in his last reply might indicate this process isn't selecting just OOG colors which might make it's selection process an issue.

Perhaps I mis-spoke in referring to gray scale images. A gray scale image can be encoded in a single channel file or as a 3 channel RGB file in which all the RGB values are equal. My point was that your black to white wedge scale in Adobe RGB can be fully encoded in sRGB since the luminance ranges of the two spaces are equal. My original points are demonstrated in this plot.

Bill

[digitaldog]

My point was that your black to white wedge scale in Adobe RGB can be fully encoded in sRGB since the luminance ranges of the two spaces are equal.

And Photoshop's soft proof honors that, the other technique doesn't if I'm understanding the comments correctly. So what to do? Use an interesting technique to select OOG/clipped colors? Use the Photoshop OOG overlay and not select those colors to then do some kind of edit?

Or as I've proposed from the beginning, soft proof with the profile, let it do it's business expect in rare cases where the soft proof, NOT the OOG overlay indicates some selective editing is in order, as I illustrated with the magenta cloth losing detail?

[D Fosse]

All right. I'd like to zoom in on one specific aspect of this, just for one moment. No examples, no color space plots, just a simple question:

If you convert a file and you get clipping because a color is out of gamut:

How can it possibly show up in the converted file, other than as 0 or 255 in one or two channels? It's just not possible for an out of gamut color to turn up in the middle of the histogram for all channels. If it did, it wouldn't be out of gamut, would it?

I know the histogram is out of fashion and you're supposed to ignore it. But let's just treat it as a diagnostic tool, nothing more. If you see the blue channel solidly rammed against the left wall, what else could it be than gamut clipping?

[bjanes]

I know the histogram is out of fashion and you're supposed to ignore it. But let's just treat it as a diagnostic tool, nothing more. If you see the blue channel solidly rammed against the left wall, what else could it be than gamut clipping?

Out of fashion and best ignored according to whom? A proper histogram is a valuable tool. One prominent author, Jeff Schewe, in his writings on ACR has indicated that when one is rendering into a narrower color space such as sRGB or AdobeRGB and the histogram hits the wall with one color, this may be due to saturation clipping and one should try rendering into a wider color space such as ProPhotoRGB. This has worked many times for me. In some cases, one can eliminate such clipping by adjusting the exposure, but this darkens the image and is not recommended.

Bill

[D Fosse]

Exactly, Bill, and this is my hypothesis: When you see the histogram hitting the wall for one color, left side or right side, that is the gamut clipping. So clipped colors have a common feature: one channel is either 0 or 255, black or white.

Most discussions on gamut clipping tend to concentrate on the 255 side. I don't know why, but maybe because that's the typical clipping you get in a very typical scenario - the sunset. And a clipped sunset is very objectionable to everyone. Or a bright red or yellow flower, also a common example.

But, at least for the type of photography that I do, I see clipping on the 0 side just as frequently. And it can be just as objectionable, because it tends to kill light and "air" in these areas.

So. Can this common feature - 0 or 255 - be used to selectively target these areas, with minimum collateral damage to unclipped areas?

[digitaldog]

Exactly, Bill, and this is my hypothesis: When you see the histogram hitting the wall for one color, left side or right side, that is the gamut clipping. So clipped colors have a common feature: one channel is either 0 or 255, black or white.

But is that telling us via a selection of the channel if it's color clipping or tonal clipping? There lies my confusion and the reason why Photoshop's OOG overlay doesn't show me areas that are tonal clipping but does show me color clipping. A properly built Histogram shows us the difference too. So it's useful, no question.
Clipping colors and tonal clipping still share a common feature? If the concept you outline is to select OOG colors, something I'd prefer Color Range to do on RGB files or anything setup in Proof Setup, we appear to be selecting tone and color clipping and I'd think we'd only want to select and edit color clipping.

If you convert a file and you get clipping because a color is out of gamut:

Colors or tones or both?

[D Fosse]

Yes, that is indeed the main problem. The distinction seems to be whether all channels clip, or just one. Or perhaps two, but at any rate not all three.

But how to separate them? Maybe subtracting low and high Lab values might be possible. In my posts above I suggested merely ignoring this, as there most likely isn't any color information there anyway.  But maybe there's a better way.

This is getting very elaborate...and ultimately perhaps not worth it. But if you look at it from the other end - not with the objective to "fix" all clipping, which is clearly overkill - but to avoid desaturating unclipped areas in the event some remapping is required anyway. Just as a protective mask when brushing, or something similar.

[digitaldog]

Yes, that is indeed the main problem. The distinction seems to be whether all channels clip, or just one. Or perhaps two, but at any rate not all three.
But how to separate them?

Good question. I'm not sure we can. I was hoping we could select 0/0/0 from each color channel and add those selections to a new, single alpha channel, then subtract anything that's neutral, avoiding color and thus OOG. But Color Range doesn't have this capability. Two other issues with the technique as I understand it:

1. The Color Range selection is based on the Eyedropper sampling. So obviously setting point vs. 3x3 vs. other settings affect what Color Range selects.
2. Fuzziness also affects the selection. No feather would be more precise in what gets selected. But the final selection channel if loaded and some edit applied (you used Channel Mixer) can produce some ugly selections of edges.

So I'm not sure this technique can work, again based on my understanding of the steps. We want only OOG colors, not clipped colors or rather clipped tones. We want to select OOG only so we can edit just those pixels but that's looking difficult to do with the tools provided.

So this takes me back to one possible solutions. Just soft proof, let the profile handle OOG and if an area looks poor, like the Magenta fabric that has no detail, deal with that selectively prior to conversion while soft proofing. Forget the OOG overlay completely. Use the sponge tool set to desaturate with a low level of strength (flow) and along with the Fade command if necessary to fix this problem pretty quickly. The technique can be done on a layer so it's "non destructive". Instead of using Sponge tool:

1.Create a new layer above the image, set blend mode to Saturation.
2.Set color to Black (or any neutral color value).
3.Select a brush with low opacity and paint onto OOG to desaturate. The Fade command is useful to fine tune but operates after each brush stroke.
If you go too far, set color to fully saturated color (R0/G255/B0) Paint saturation back in.


The other alternative is if the soft proof looks OK, just pick the rendering intent, and move on.

[MarkM]

All right. I'd like to zoom in on one specific aspect of this, just for one moment. No examples, no color space plots, just a simple question:

If you convert a file and you get clipping because a color is out of gamut:

How can it possibly show up in the converted file, other than as 0 or 255 in one or two channels? It's just not possible for an out of gamut color to turn up in the middle of the histogram for all channels. If it did, it wouldn't be out of gamut, would it?

You should test this theory with LUT based profiles such as printer profiles. This will allow you to also test with different rendering intents that are more complex than simple matrix multiplications. You will find that you often have out of gamut colors that get mapped into the destination space with some breathing room and don't look like they are clipping. For example for the ProPhotoRGB color [10, 250, 10] photoshop give a LAB value of [86, -128, -128]. Converted to Epson's 3880 standard profile give an RGB value of [134, 252, 45] = LAB [87, -84, 85]. The gamut warning says it's out of gamut, the color shift is significant, but the technique of finding clipped color values will fail to identify this as out of gamut.

[digitaldog]

You should test this theory with LUT based profiles such as printer profiles. This will allow you to also test with different rendering intents that are more complex than simple matrix multiplications.

You've outlined yet another problem with Adobe's OOG overlay. Toggling the differing RI's don't produce any difference.

[MarkM]

You've outlined yet another problem with Adobe's OOG overlay. Toggling the differing RI's don't produce any difference.

I'm not sure it should. Unless I'm misunderstanding something, the rendering intent shouldn't change whether a color is out of gamut — it should only change how out-of-gamut values are mapped to the destination.

[digitaldog]

I'm not sure it should. Unless I'm misunderstanding something, the rendering intent shouldn't change whether a color is out of gamut — it should only change how out-of-gamut values are mapped to the destination.

What I've done is opened an image in ProPhoto RGB and set an Epson profile for soft proofing. I then ask to see the OOG overlay. I'd expect that as I toggle between Perceptual and RelCol, the overlay would change somewhat. But perhaps you're right now that I think of it, RelCol clips OOG to the boundaries, Perceptual would affect other colors. If true, it still makes the overlay far less useful than a soft proof which of course does change what we see on-screen.