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Author Topic: What changes do you usually make when Softproofing?  (Read 30158 times)

D Fosse

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Re: What changes do you usually make when Softproofing?
« Reply #40 on: May 31, 2015, 02:37:45 pm »

OK, I've attached an example of the channel mixer method (not a good one, but the best I could find in a hurry).

First an Adobe RGB original.

Converted to sRGB, the lower part of the green water clips to 0 in the red channel. So open the Color Range dialog, and use the eyedropper to pick blacks (with only the red channel active in the Channels panel). Obviously, this will pick all blacks, including true black - but that doesn't matter because this doesn't contain any color information anyway. So all channels are equal here and nothing will change.

Go back to RGB and put a channel mixer layer on top, with red channel as output, settings +50 red, +25 green and +25 blue. Set opacity as needed to get a good blend.

The third example is the corrected red channel with channel mixer. Everything looks good, and no more clipping.

In this particular example it actually didn't do much visually, but it shows the principle.
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digitaldog

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Re: What changes do you usually make when Softproofing?
« Reply #41 on: May 31, 2015, 02:42:57 pm »

Converted to sRGB, the lower part of the green water clips to 0 in the red channel.
None was black prior to conversion?
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So open the Color Range dialog, and use the eyedropper to pick blacks (with only the red channel active in the Channels panel).
Ah, that was what I was missing thanks. You're targeting via eyedropper, not a preset (Shadows). I assume you're viewing the numbers to nail black (zero).
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Obviously, this will pick all blacks, including true black - but that doesn't matter because this doesn't contain any color information anyway. So all channels are equal here and nothing will change.
Got it. Was there a reason you didn't do the same with Red and Blue, it's just this image didn't have a black in the other channels?

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D Fosse

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Re: What changes do you usually make when Softproofing?
« Reply #42 on: May 31, 2015, 04:59:50 pm »

No, this particular red channel clipping happens in the conversion to sRGB. In Adobe RGB it's within gamut.

There is in fact a very tiny amount of blue channel clipping in the sun-lit foliage, but not enough to bother with.

As I said, I could probably have found a better example - one in which the clipping is more objectionable than it is here - but the basic procedure is illustrated fairly well. The point is that only the clipped areas are targeted, and very specifically so, leaving everything still in gamut strictly alone. So you don't lose colors you haven't already lost, so to speak.

With this method it's also possible to "reuse" the mask for, say, a selective color layer, to compensate for any unwanted hue shifts.
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digitaldog

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Re: What changes do you usually make when Softproofing?
« Reply #43 on: May 31, 2015, 06:01:04 pm »

No, this particular red channel clipping happens in the conversion to sRGB. In Adobe RGB it's within gamut.
I'm looking for something color space agnostic, does this still apply?
I'm still not clear on why the image areas that are black in the channel represent OOG.

I was hoping I could do something with Calculations but I'm not getting anywhere. I tried converting from ProPhoto to sRGB then back, using Difference to produce something I could select. Doesn't appear to be working as expected, the result isn't anything like the OOG overlay.

I'm getting to the point where I'm thinking my original idea of just using the profile to handle this is the way to go. If we convert using the profile and then attempt to examine the results to select something, in a copy, it appears that we're back to asking the profile to do all the work anyway.

It's too bad that using Color Range to select OOG doesn't work on the current profile selected in Proof Setup. Only CMYK in Color Settings. But then I would have to believe that the OOG being selected is correct in the first place and I don't know if that's really true. I could try using Color Range on RGB data using the CMYK profile, then convert and see in ColorThink if the two match.
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D Fosse

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Re: What changes do you usually make when Softproofing?
« Reply #44 on: June 01, 2015, 04:50:05 am »

I'm still not clear on why the image areas that are black in the channel represent OOG.

Well, that's the clipping. Anything that wants to go higher than 255 or lower than 0 in any channel, in any specific color space, is out of gamut. So it clips to 255 or 0. You could consider that a definition of OOG (among others).

You'll have to excuse me for telling you things you already know; I just need to establish the logic behind this...

Of course, what confuses the issue somewhat is the fact that "true" black or "true" white will also be included in the selection. In any given channel, the two can't be separated. But as already concluded, this is of no practical consequence because with pure black or white the channels are already equal, and nothing will change. So that can simply be ignored.

(side note - in "phenomenological" terms, I think you could consider gamut clipping and exposure clipping the same. It's just anything outside the surface of the color space, or color sphere in a more general view. Exposure clipping is just a special case because it affects all channels, so nothing can be recovered).

Now. The catch here, what makes this somewhat less than an ideal tool for dealing with OOG, is the fact that it only works on an already converted file. Soft proof does not reflect the clipping in individual channel view (I wish it did!); only in the composite RGB. So to use this method you either have to go the roundabout way of doing it on a copy and reimport the selection/mask - or do what I called a "quick and dirty" repair using the channel mixer.

Either way, you still have the advantage of not touching in-gamut areas, so there's no need for "wholesale" desaturation of all blues, all greens and so on. As I said, it's a bit of work, but every once in a while it can be worth it. For normal everyday work it usually isn't.

As for the color space agnostic bit, I don't quite follow-? As you well know, clipping can't be color space agnostic, it clips in this space but not the other.


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Brian Gilkes

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Re: What changes do you usually make when Softproofing?
« Reply #45 on: June 01, 2015, 07:23:42 am »

I apologise for leaving the table. There were a lot of other activities on. I did not expect such a long thread and will work through it all carefully. The reference to OOG was intended as a minor point. I very seldom have OOG colours . When i do it is usually quite small areas. If using HSL I select the colour as narrowly  as possible using the "colour wheel" sliders and then juggle desaturation and hue to return detail with minimum disturbance of colour appearance. This normally takes no more than a minute or two.If a longer method seemed justified i might use an action to create a set of luminosity channels and set HSL layers over them. That might take a few minutes. I am somewhat concerned re comments that the OOG indication is inaccurate. Would it be beneficial to use ColorThink as an editing aid?
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digitaldog

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Re: What changes do you usually make when Softproofing?
« Reply #46 on: June 01, 2015, 09:30:02 am »

Well, that's the clipping. Anything that wants to go higher than 255 or lower than 0 in any channel, in any specific color space, is out of gamut. So it clips to 255 or 0. You could consider that a definition of OOG (among others).
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.
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Of course, what confuses the issue somewhat is the fact that "true" black or "true" white will also be included in the selection.
That's my concern, and it appears the current OOG overlay doesn't target those true blacks or true whites for one.
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In any given channel, the two can't be separated. But as already concluded, this is of no practical consequence because with pure black or white the channels are already equal, and nothing will change. So that can simply be ignored.
I guess so  ;D
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Now. The catch here, what makes this somewhat less than an ideal tool for dealing with OOG, is the fact that it only works on an already converted file.

Understood. That's not a huge, big deal and we did discuss that the profile is used for this operation so there's no way to put any toothpaste back into the tube if you will from this approach. It seems to underscore my original concept to just examine visually what the profile will do via a soft proof (display gamut limitations recognized) select a rendering intent one visually prefers and letting the conversion take place. That could allow for some output specific edits to be applied prior to the conversion while viewing the soft proof if necessary.
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As for the color space agnostic bit, I don't quite follow-? As you well know, clipping can't be color space agnostic, it clips in this space but not the other.
I could have been more clear by saying destination color space agnostic. I was confused by your statement about sRGB as if the technique was based upon that destination color space. I'm looking for an alternative to "just use the profile" that would work with all destination profiles, working space or output.
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digitaldog

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Re: What changes do you usually make when Softproofing?
« Reply #47 on: June 01, 2015, 09:33:15 am »

I am somewhat concerned re comments that the OOG indication is inaccurate. Would it be beneficial to use ColorThink as an editing aid?
I don't see it on all images in all color spaces. I do see it here:
http://digitaldog.net/files/Printer%20Test%20file.jpg
The image in ColorMatch RGB. If I select that in Proof Setup and use the OOG command, I see some areas of overlay and of course I shouldn’t. Same in Lightroom, I think they share the same code.
As for ColorThink, it's ideal but you have to feed it tiny files or it will barf. 300x300 pixels is what I usually send to CT for analysis which means severe resampling to plot the image.
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D Fosse

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Re: What changes do you usually make when Softproofing?
« Reply #48 on: June 01, 2015, 03:49:52 pm »

Well the OOG overlay doesn't work that way, at least as I see it.

I'm getting a very close congruence, and I still think my method holds up. If anything, the OOG overlay is somewhat conservative and there seems to be a small threshold before it kicks in. That makes sense. I still insist that areas that are clipped in the converted file will show up as solid black or solid white in individual channels, since they are clipped to either 0 or 255.

Another example.

In the first I used the Lightroom OOG overlay, raw original soft proofed to sRGB.

Second "my method" showing blue channel clipping - plus black as noted, but there's very little of that here. Third ditto green channel clipping. There's no red channel clipping here.

As this is, again, a low-key image, all the clipping occurs in the low end. High-end clipping is what you get in your typical sunset, and that would show up as white.

If you add these two, the blue and the green channel, you get pretty much pixel-perfect what the Lr OOG overlay indicates.
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D Fosse

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Re: What changes do you usually make when Softproofing?
« Reply #49 on: June 01, 2015, 04:02:56 pm »

BTW I'm just using sRGB as a convenient small-gamut space here. There's no special significance to sRGB.
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digitaldog

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Re: What changes do you usually make when Softproofing?
« Reply #50 on: June 02, 2015, 09:50:17 am »

I'm getting a very close congruence, and I still think my method holds up.
I'll continue to to look into this, thanks!
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digitaldog

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Re: What changes do you usually make when Softproofing?
« Reply #51 on: June 02, 2015, 01:07:19 pm »

I'm getting a very close congruence, and I still think my method holds up. If anything, the OOG overlay is somewhat conservative and there seems to be a small threshold before it kicks in.
I'm seeing the conservative nature you point out in a recent test but I'm not certain about close congruence but it may not matter, nothing I know of proves the OOG overlay is 'correct'. Maybe the opposite.
I uploaded my test file which is part of the Gamut Test File. Here's what I did:
1. Duplicate the ProPhoto RGB image, convert to sRGB.
2. View first the Red Channel, use Color Range with the eyedropper to select a color/tone. I made sure with the info palette I was hovering over pixels at 0/0/0. Note, the one attribute I'm not sure of is Fuzziness. I see two different values in your examples. All blacks in Red Channel gets selected. I then used Save Selection and targeted the original ProPhoto RGB image to create an Alpha Channel.
3. Repeat step #2 on Green and Blue channel.
4. Back in the original ProPhoto RGB image I used Load Selection three times (adding the selection from Green and Blue Alpha to the Red to produce one selection of all three). I then saved that composite into a single Alpha Channels.
I went back to the sRGB image and reset History so I now have two images in ProPhoto RGB to compare.
Now I can show the selections from each, one is OOG using the old Photoshop command, the other the custom selection. Here's the results of the two where 'Black' is the selection:


On the left is OOG from Photoshop where I've set the overlay to black, 100%. On the right is your technique. Not identical, but an interesting selection.
So assuming I'm doing this correctly and can trust the selection, the next thing I have to test is what to do with the OOG colors selected.

I've uploaded the TIFF with all the Alpha channels if anyone wishes to comment. It's set with the Quick Mask on so at least on this end, after saving and opening again, that is 'sticky' so you'll see an overlay I believe although based on your PS preferences, it may not be in black at full opacity. It's here:

http://digitaldog.net/files/OOG.tif
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digitaldog

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Re: What changes do you usually make when Softproofing?
« Reply #52 on: June 02, 2015, 01:20:14 pm »

Couple further comments. I didn't target white or 255/255/255 from the three channels in this image but I don't see any such values in the individual color channels so I hope that's OK.

I have a selection but I'm not sure what to do and how far to go with any edit. With the OOG overlay, what's useful is it begins to disappear as you affect the image. But of course, doing so until it's even close to fully disappearing hoses the image.

I converted one copy from ProPhoto RGB to sRGB to use as a visual guide. Now the trick is using the selection to do something to get it into gamut and appear better than the other copy using the profile and I'm not sure that's possible.

The selection technique is pretty cool, no question. But I'm not sure what to do after producing it. The sRGB version looks OK. The one area I don't see detail is the very vivid magenta towel in the upper right corner. Using Channel Mixer, a tool I'm far from savvy with and lowering Red a tad does appear to bring back detail but unfortunately affects other colors with red component in a less than ideal way. Plus 86 Red (from 100) really helps the magenta but not the yellow's and oranges elsewhere.
« Last Edit: June 02, 2015, 01:25:23 pm by digitaldog »
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D Fosse

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Re: What changes do you usually make when Softproofing?
« Reply #53 on: June 02, 2015, 03:40:58 pm »

Ah well, that's a tricky one... ;D

Here you have pushed even ProPhoto almost to the limit, and the sRGB clipping here is so massive that I won't even attempt it. It'll just be an across the board desaturation.

I did manage to make an Adobe RGB version without clipping - although I admit to cheating a bit, as I used your sRGB masks. But I think it clearly does look better than just letting the profile do it, which is what I wanted to find out (attached with ARGB profile embedded). In particular, the magentas and the central yellow regain texture that was mostly absent (even viewed on a wide gamut monitor).

There's no way this beast can be tackled with a single mask. This one has to be dealt with mask by mask, channel by channel, color by color.

A few additional selective color and hue/sat adjustments were required after the basic mask treatment - not to desaturate further, but to compensate for hue shifts. Most colors basically survive.

The masks seem sound. Yes, there are a few small discrepancies with the Photoshop overlay, mostly in oranges - which is because there is a little highlight clipping in the red channel here.

I spent a little more than an hour on this. Is it worth it? Could well be. Thanks for an interesting hour  ;)

(had to post as jpeg with channels stripped)
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digitaldog

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Re: What changes do you usually make when Softproofing?
« Reply #54 on: June 02, 2015, 03:56:16 pm »

Ah well, that's a tricky one... ;D
That was the plan, the rest of the test file is equally difficult!
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Here you have pushed even ProPhoto almost to the limit, and the sRGB clipping here is so massive that I won't even attempt it. It'll just be an across the board desaturation.
In the end, I just use the old Sponge Tool to carefully deal with the magenta cloth, then using Fade, brought it down to see some detail there in sRGB. Considering what role sRGB plays for me, it isn't worth the effort, it's just going onto the web. What's interesting is converting to my Epson 3880 profile, plenty of detail after the conversion both on-screen and on the print. So part of the fault is Satanic RGB.
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There's no way this beast can be tackled with a single mask. This one has to be dealt with mask by mask, channel by channel, color by color.
Not worth the effort to post as an sRGB image to the web or mobil devices.
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The masks seem sound. Yes, there are a few small discrepancies with the Photoshop overlay, mostly in oranges - which is because there is a little highlight clipping in the red channel here.
Cool. I do like the mask technique, so that's worth all the effort (on this end).
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I spent a little more than an hour on this.
Ouch. 
So another tactic that didn't seem to work was using ColorThink Pro to build a ColorCast profile. I used an sRGB to CMYK transform with the idea I could then use Color Range to select OOG. It worked but not like either your masking technique or Photoshop's OOG. The CMYK profile selected plays a role. I really wanted an sRGB profile that lived in a CMYK shell to fool Photoshop to use Color Range. That part worked somewhat, it could be accessed and it perfectly matches the OOG overlay but again, since the CMYK profile part of the ColorCast process plays a role, I have no idea what to use for that part of the transform.

What we need is for Adobe to tie the current Proof Setup to be accused in Color Range to select OOG, not the CMYK profile in Color Settings. We need them to fix the inaccuracies of what's defined as OOG. Then we need two or three OOG colors to represent small, medium and large amounts of OOG. Until then, I'm not convinced I'd manually do anything much more than convert after viewing a soft proof and maybe doing a < 5 minute selective edit in areas  like we see in the Magenta cloth.

Oh BTW, I tried converting the image to sRGB using the V4 ICC Profile that provides a Perceptual rendering intent and the results were even worse on the Magenta cloth than using RelCol.

Thanks for your time, I learned a lot!
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D Fosse

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Re: What changes do you usually make when Softproofing?
« Reply #55 on: June 02, 2015, 04:24:43 pm »

An hour is nothing for me. Back when I had a darkroom (the chemical kind), I could spend a week on one single negative. That was my Ansel Adams period... of course nobody else saw any difference.

These days, as a full-time employed photographer, where deadlines queue up every day, I usually don't have that luxury. But every once in a while, an image is considered so important that I can spend an hour or two on it. And it usually shows. But most of it is CMYK for books and magazines, so most of the time is spent getting around the inherent limitations.

An interesting discussion. I wouldn't mortgage my house on this, not yet, but I have a feeling there's something here. I'll keep trying it out, and I'm sure this will come up again  ;)
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MarkM

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Re: What changes do you usually make when Softproofing?
« Reply #56 on: June 07, 2015, 04:46:57 am »

Just a side note —

Here's a test image that I made for exploring OOG issues. The colors in the image are from outer surface of the prophoto space in xyY projected onto the xy plane. Since the colors are from the outer surface of the space, every color will have at least one coordinate that is 255. This means that the entire colored area of the image should be outside the gamut of sRGB. Photoshop's gamut warning overlay shows a few stripes of color that it thinks are within the sRGB gamut. I'm not sure why it does this, but Andrew has mentioned on several occasions that it's not very accurate.

One interesting thing about this image is that even though the entire images is within the prophoto gamut, D Fosse's technique will suggest the whole colored area is clipping. It's an example of the fringe case where 255 really is 255 rather than a greater value that has been clipped.

Another thing this image illustrates is the danger of using xy chromaticity to evaluate gamut. If you overlay the sRGB triangle onto this you might think the values in the center of the image should be within the sRGB gamut, but they're not. Even though sRGB can contain colors with these xy values, these particular colors are out of gamut because they sit outside the 3d hull of the sRGB solid in xyY space.
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D Fosse

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Re: What changes do you usually make when Softproofing?
« Reply #57 on: June 07, 2015, 07:06:39 am »

Something just occurred to me, maybe a flaw in my reasoning. When you look at an individual channel in Photoshop, it is displayed according to your gray working space, not the original color space of the file. This mainly affects the TRC, but maybe it also affects the clipping point, especially considering the linear section in the sRGB TRC. I need to think about this.

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.
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digitaldog

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Re: What changes do you usually make when Softproofing?
« Reply #58 on: June 07, 2015, 12:27:41 pm »

Something just occurred to me, maybe a flaw in my reasoning. When you look at an individual channel in Photoshop, it is displayed according to your gray working space, not the original color space of the file.
I don't see the numbers changing, just the preview which kind of makes sense. Much like the numbers of an untagged document don't change as you update the RGB working space, only the preview.
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Re: What changes do you usually make when Softproofing?
« Reply #59 on: June 07, 2015, 12:36:26 pm »

This means that the entire colored area of the image should be outside the gamut of sRGB. Photoshop's gamut warning overlay shows a few stripes of color that it thinks are within the sRGB gamut. I'm not sure why it does this, but Andrew has mentioned on several occasions that it's not very accurate.
Here's an example of OOG being shown that shouldn't using my old Printer Test File which was in ColorMatch RGB and soft proofed to the same profile. Green is OOG overlay:

Doing the same in Lightroom produces the same issue although it's not identical. The two app's don't correspond.
So going back to your investigation, does it make sense to suggest that while PS's OOG overlay isn't accurate in all cases, it's closer than using the Mask built from other RGB channles? The former doesn’t provide a way to select these colors which would be useful, the later does but it sounds like it might not be an accurate selection of OOG. Where does that leave us?
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