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Author Topic: ipf8400 gamut  (Read 25094 times)

Robert Ardill

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Re: ipf8400 gamut
« Reply #40 on: September 23, 2014, 03:05:06 pm »

I know you think you did, anyone else here agree?

Before everyone jumps on the bandwagon and disagrees I seriously suggest you look at the ArgyllCMS information and ask Graham Gill for his views on the subject.

Robert
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digitaldog

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Re: ipf8400 gamut
« Reply #41 on: September 23, 2014, 03:08:38 pm »

Before everyone jumps on the bandwagon and disagrees I seriously suggest you look at the ArgyllCMS information and ask Graham Gill for his views on the subject.
How will that change the processing of my images in ACR/LR and output to my printer using a profile that wasn't a mile from ArgyllCMS? All I (and at least one other person) is asking for is proof of concept using our tools and workflow that suggest your idea of using a smaller gamut than ProPhoto RGB is going to produce a better print.
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Robert Ardill

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Re: ipf8400 gamut
« Reply #42 on: September 23, 2014, 03:22:18 pm »

How will that change the processing of my images in ACR/LR and output to my printer using a profile that wasn't a mile from ArgyllCMS? All I (and at least one other person) is asking for is proof of concept using our tools and workflow that suggest your idea of using a smaller gamut than ProPhoto RGB is going to produce a better print.

ArgyllCMS is not relevant ... I use both Argyll and i1Profiler and the same issues are present with both.  What is relevant is that Graham Gill, who, as I said, is the author of ArgyllCMS and is a recognized expert in the area is really worth listening to.  He has forgotten more about profiles that either you or I know Andrew (I'm making an assumption here about your knowledge, which may not be entirely fair, but I base the comment on what you've been saying).

Robert
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digitaldog

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Re: ipf8400 gamut
« Reply #43 on: September 23, 2014, 03:37:22 pm »

ArgyllCMS is not relevant ...
Neither is the link you provided (in terms of not using ProPhoto RGB for a smaller gamut working space).
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Robert Ardill

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Re: ipf8400 gamut
« Reply #44 on: September 23, 2014, 04:32:13 pm »

OK, well I’ve devised a test that does demonstrate at least to some extent the issue we’ve been discussing.

I took a file with a sort of Granger Rainbow that I constructed myself in sRGB in 16-bit mode.



I then converted a duplicate of this image to ProPhoto.

I then converted both images to a destination profile (I used a Canson profile so it’s entirely 3rd-party and out of my control).  The conversion was perceptual with BPC on in both cases.  This is the data that would be sent to the printer: the job of the CMM is done.

I then placed one image above the other as layers in Photoshop and set the upper layer to Difference.  I applied a Levels adjustment above the two layers to make the difference more apparent.  This is what it looks like:



The test is not conclusive as the differences could be due to rounding errors … or they could be due to the compression of the ProPhoto space to the smaller printer space.  My guess is that the noise-like differences are due to rounding and the bands and lines and swirls due to compression.  I don't think it's a coincidence that the biggest differences are at the dark end as the saturated dark colors have to be squeezed into a small volume.

The only conclusive way of doing this, to my mind, is to look at the mapping algorithm … or at the profile mapping using GamutVision or Chromix.  This is a bit like asking to see a Black Hole … you can show the maths, you can show the stars twirling around seemingly nothing … but you can’t show the Black Hole.  Or at least I can’t for this particular black hole :).

Robert
« Last Edit: September 23, 2014, 04:51:20 pm by Robert Ardill »
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Robert Ardill

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Re: ipf8400 gamut
« Reply #45 on: September 23, 2014, 04:41:25 pm »

Neither is the link you provided (in terms of not using ProPhoto RGB for a smaller gamut working space).

You're a hard man to convince Andrew  :).  Here is a quote from the link I provided: "The typically expected behaviour of perceptual intent gamut mapping, is to compress any areas of the source gamut that lie outside the destination gamut, but for areas that fall within the destination gamut, change them as little as possible, consistent with keeping smooth and proportional with respect to the compressed colors. This preserves the source "look" as much as possible, while ensuring that out of gamut colors are smoothly brought within the destination gamut."  (underline is mine).

That is the problem: you can't maintain smooth and proportional colors within the destination gamut if you have had to compress from a much larger color space without also compressing the colors inside the destination gamut.  There are plenty of sophisticated algorithms that minimize this compression ... and the more successful ones probably do a good enough job that we can use ProPhoto and perceptual mapping without having to worry too much ... but then we are depending on very good profiles.  There's no reason to assume that the profiles supplied by paper manufacturers, for example, would be this good.

Robert
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digitaldog

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Re: ipf8400 gamut
« Reply #46 on: September 23, 2014, 04:57:35 pm »

That is the problem: you can't maintain smooth and proportional colors within the destination gamut if you have had to compress from a much larger color space without also compressing the colors inside the destination gamut.  There are plenty of sophisticated algorithms that minimize this compression ... and the more successful ones probably do a good enough job that we can use ProPhoto and perceptual mapping without having to worry too much ... but then we are depending on very good profiles.  There's no reason to assume that the profiles supplied by paper manufacturers, for example, would be this good.
And again, none of this has any bearing on the output, nor the options we have for mapping OOG to smaller colors using matrix profiles, or going from raw to an encoding color space using an Adobe raw conveter. Show us where the larger ProPhoto gamut from ACR/LR is an issue, and if possible, doing so such we can output the results and see this for ourselves. The Granger Rainbow doesn't work in that respect either. It didn't come from raw data or was processed from ACR/LR who's internal color space is processed using ProPhoto gamut.

You saw the video. Short of providing the raws, the Gamut Test File has all the data I can push out of the ACR pipeline. I can go smaller. And I can print both iterations. What can you provide in a similar fashion that supports your hypnosis that a smaller encoding from raw is going to produce a better master that can be printed and then converted to other color spaces for whatever need might arise.

You either don't want to see the workflow or can't. I've got raw data. I've want to process it with a product that uses ProPhoto gamut. I want all the color and tone available for all images so I can edit them in a working space then print them. I can pick ProPhoto or something smaller. Why should I pick smaller gamut from the raw processor? Illustrate that when I also need a wide gamut print output (any modern Epson will do), the smaller encoding space you suggest I pick produces a better print.
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Robert Ardill

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Re: ipf8400 gamut
« Reply #47 on: September 23, 2014, 05:10:51 pm »

And again, none of this has any bearing on the output, nor the options we have for mapping OOG to smaller colors using matrix profiles, or going from raw to an encoding color space using an Adobe raw conveter. Show us where the larger ProPhoto gamut from ACR/LR is an issue, and if possible, doing so such we can output the results and see this for ourselves. The Granger Rainbow doesn't work in that respect either. It didn't come from raw data or was processed from ACR/LR who's internal color space is processed using ProPhoto gamut.

You saw the video. Short of providing the raws, the Gamut Test File has all the data I can push out of the ACR pipeline. I can go smaller. And I can print both iterations. What can you provide in a similar fashion that supports your hypnosis that a smaller encoding from raw is going to produce a better master that can be printed and then converted to other color spaces for whatever need might arise.

You either don't want to see the workflow or can't. I've got raw data. I've want to process it with a product that uses ProPhoto gamut. I want all the color and tone available for all images so I can edit them in a working space then print them. I can pick ProPhoto or something smaller. Why should I pick smaller gamut from the raw processor? Illustrate that when I also need a wide gamut print output (any modern Epson will do), the smaller encoding space you suggest I pick produces a better print.

As I've already said, Andrew, I'm not interested in doing prints to try to demonstrate this.  I'm one of these people who believes the maths, especially when the maths is nothing more than a computer algorithm.  If you look at a perceptual ProPhoto to Destination mapping with mapping vectors you will see how the data is being shifted.  If you do the same thing with a smaller space like Adobe RGB you will see that the shifting is less.  If you don't believe this then what can I say?

If you want your image to be in a state that it can, at a later stage, be output to any device you choose, not knowing at this stage what this device might be or how large its gamut might be, well then stay in ProPhoto ... of course.  Keep your options open.  But if you know what your output devices will be (web and printer with specific papers for me) and you want the best result then I think you would be wise to keep your image gamut/s as close to the output device/s as possible.  But it's a free world out there (sort of) so why don't you stick to ProPhoto and I'll wander around picking the workspace that I think is best?

Robert
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digitaldog

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Re: ipf8400 gamut
« Reply #48 on: September 23, 2014, 05:17:14 pm »

As I've already said, Andrew, I'm not interested in doing prints to try to demonstrate this.
Well then all you need to deal with is sRGB or Adobe RGB if screen output is your only goal. A lot of us here need a much wider gamut output. In fact, isn't this post about printing? Isn't the topic the gamut of a Canon printer?
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If you look at a perceptual ProPhoto to Destination mapping with mapping vectors you will see how the data is being shifted.
I don't care (as long as the image appears as I desire). Color management isn't perfect (far from it). The proof is in the output. Show us where and how, going from ProPhoto to even Adobe RGB is an issue to the display (as long as we're using a wide gamut display system).
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If you do the same thing with a smaller space like Adobe RGB you will see that the shifting is less.
OK, provide a raw image where I can process using both options and I'll let you know what I see on-screen.
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Keep your options open.
Exactly WHY I use ProPhoto RGB and not Adobe RGB (1998) (the later is too small for output to my printer, something you say you don't care about. I do).
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But if you know what your output devices will be (web and printer with specific papers for me) and you want the best result then I think you would be wise to keep your image gamut/s as close to the output device as possible.
Prove it! That's all I'm asking. And is this methodology now for print too (something you say you are not interested in testing)? Make up your mind. Again, for the 4th time. I've got a slew of raw images. Some very saturated. Some not. Some will be printed. Some will not. I've got a raw processor using ProPhoto gamut for all processing. I've got to pick an encoding color space. You seem to be suggesting ProPhoto is sometimes the wrong answer. Show us. Simple as that.
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Wayne Fox

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Re: ipf8400 gamut
« Reply #49 on: September 23, 2014, 05:27:58 pm »

I tested some of this stuff years ago when using ppRGB was just coming into it’s own, (at the time I actually felt the size of the space was problematic because of issues I would see, only to discover it was from working in 8bit - a big deal back then because hard drive storage was immensely more expensive).  I actually tried to find circumstances where files and prints would look better converted directly to sRGB  and worked in Photoshop vs ppRGB.  It just doesn’t happen.  I tried 20 or 30 different shots, and the end results were virtually identical.

Certainly if you wreak havoc on your file in Photoshop in ppRGB the results will be ghastly. But for photographers who do that, forcing them into a smaller space won’t help ... they’ll come out bad anyway.

As far as the math, as a photographer I”m interested in the results.  Just assuming the math may show a problem doesn’t mean it will in practical use.  This doesn’t.  In fact far more photographers get into trouble working in sRGB space on their files than they do prophotoRGB ... I print them every day here in my store.

To Andrews point, it’s clear that not using ppRGB can sometimes cost you in print quality and also limits potential future options.  Is there an example in a photographer workflow where using ppRGB instead of a smaller space will result in a worse print/image? (other than circumstances I mentioned 2 paragraphs up)
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Robert Ardill

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Re: ipf8400 gamut
« Reply #50 on: September 23, 2014, 05:58:47 pm »

I'll answer both of you (Wayne and Andrew) at the same time to save typing and since you're pretty well on the same page.

Firstly, of course I'm interested in printing.  Almost all of the money I make from photography and painting comes from my prints and I print all of my images personally and with great care.  What I'm not interested in doing is trying to demonstrate to you by doing prints what I can understand in theory and see in the profile mappings: I am one of these people who trusts logic and visual tools; clearly you are not, so it's up to you to do the demonstration, if you care to.  If you don't, well then some people will believe you (probably most :)) and some may think that there is something in what I'm saying.  For those who are undecided ... why don't you post a question to Graham Gill on argyllcms@freelists.org?

Secondly, I have not at all suggested that sRGB is a better working space for print than ProPhoto!  That would be absurd.  It's better for some images that have a very small gamut ... but of course it's much worse for images with a large gamut.  But, fellas, there are intermediate workspaces out there ... and perhaps they are there for a good reason. 

The example, in a photographer workflow, where using ProPhoto will result in a worse print (not necessarily a worse display) than a smaller workspace that fully (or nearly fully) covers the image gamut is, as I keep saying: the case where you print using a perceptual mapping.  But you need to define what 'worse' is.  It may look absolutely fine and you may be entirely delighted with it.  By 'worse' I mean that the colors will have been shifted more, so, for example, the match to the display image (not the soft-proofed image as this will also have the shifted colors) will be worse.  If your objective is to get a print that as closely as possible matches your monitor (not soft-proofed) image, then you may see greater differences with the large working spaces.

I fully accept and always have that using too small a workspace is even worse ... because then you will almost certainly get clipped colors if your image has saturated colors.  Just to be clear.

As for proving my point, as Andrew is insisting I do :), no, I'm not interested in taking this any further.  I've given you the information and I think it is correct (but I may be wrong!) and I think I have explained the logic as well as I can.  If you don't trust logic ... well then we're never going to agree.  Certainly Andrew's video has demonstrated that if you take an image with a wide gamut and scrunch it into sRGB you get flattening and banding etc.  Of course, that's exactly what logic says you will get: a relative mapping will do just that, whack the head down into the shoulders.  It doesn't in any way prove that ProPhoto is a better choice for all images: only that a) it is a better choice for this particular image, and b) don't convert to a smaller working space if your image gamut is wider than the smaller space.

Robert
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digitaldog

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Re: ipf8400 gamut
« Reply #51 on: September 23, 2014, 07:17:02 pm »

Secondly, I have not at all suggested that sRGB is a better working space for print than ProPhoto!  That would be absurd.  It's better for some images that have a very small gamut ... but of course it's much worse for images with a large gamut.  But, fellas, there are intermediate workspaces out there ... and perhaps they are there for a good reason. 
Such as? The question of the day which remains unanswered.
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The example, in a photographer workflow, where using ProPhoto will result in a worse print (not necessarily a worse display) than a smaller workspace that fully (or nearly fully) covers the image gamut is, as I keep saying: the case where you print using a perceptual mapping.
  Not seeing that, not with my images sorry. I know you may feel this is true based on what you've read and that's fine. It's not what I'm seeing. And again, the proof is in the print. If I don't like the Perceptual mapping, I don't use it. Simple as that.
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But you need to define what 'worse' is.
 That's subjective but then so is a color print.
You've got this idea about smaller than ProPhoto gamut working space being beneficial and that may be true, but you've failed to provide a way to backup that claim I can see. You seem somewhat more interested in gamut maps and what authors of color management software say than what the output looks like which is fine. But I'm a photographer first, a color geek 2nd and what the print or display looks like takes the prize before any gamut map. You kind of remind me of the photographer more interested in the image histogram than the image itself in terms of evaluating image quality. And unless the gamut plotter you use acts like ColorThink, I don't trust it at all for this evaluation. But even if it does behave the same way, the rubber hits the road when solid pixels map in context and we view them, either on-screen or on a print. So if you have some basis to back up your ideas that we can use to evaluate what you're suggesting, and do so with images we can look at, you're entitled to that opinion but it may not be shared by others!
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As for proving my point, as Andrew is insisting I do :), no, I'm not interested in taking this any further.I've given you the information and I think it is correct (but I may be wrong!) and I think I have explained the logic as well as I can.  If you don't trust logic ... well then we're never going to agree. 
 I trust what I can see to judge the qualities of an image workflow and you haven’t provided any means to do that.
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Certainly Andrew's video has demonstrated that if you take an image with a wide gamut and scrunch it into sRGB you get flattening and banding etc.  Of course, that's exactly what logic says you will get: a relative mapping will do just that, whack the head down into the shoulders.
 You don't have to know squat about rendering intents or color management to conduct my test and see the differences. That's where what you and I propose differ. It's not necessary to understand anything about what happens under the hood, just take one file, convert to another working space and make two prints. View, decide what looks best. Easy breazy. That's all we're asking of you but at this point, I don't think that's going to happen so let's move on.
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Wayne Fox

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Re: ipf8400 gamut
« Reply #52 on: September 23, 2014, 09:01:05 pm »

Firstly, of course I'm interested in printing.  Almost all of the money I make from photography and painting comes from my prints and I print all of my images personally and with great care.  What I'm not interested in doing is trying to demonstrate to you by doing prints what I can understand in theory and see in the profile mappings: I am one of these people who trusts logic and visual tools; clearly you are not, so it's up to you to do the demonstration, if you care to. 
As I mentioned, been there done that.  And I could not demonstrate it. It's great you trust "logic", but logic doesn't always equate to reality.  And I don't know why it's up to anyone else to demonstrate your point of view (and in fact I don't think it can be done ... well, never say never but if so the circumstances would probably be extremely rare and unique.)

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Secondly, I have not at all suggested that sRGB is a better working space for print than ProPhoto!  That would be absurd.  It's better for some images that have a very small gamut ... but of course it's much worse for images with a large gamut.  But, fellas, there are intermediate workspaces out there ... and perhaps they are there for a good reason. 
Well, the reasons the for the existence of sRGB and AdobeRGB have nothing to do with a  photographers workflow and providing an "intermediate option.  They were created for specific purposes that have nothing to do with a photographers workflow and current technology. (as opposed to ProPhotoRGB which was specially created for digital capture/printing technologies to be future proof, so the main goal was  to try and make sure all naturally occurring colors could be defined).

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The example, in a photographer workflow, where using ProPhoto will result in a worse print (not necessarily a worse display) than a smaller workspace that fully (or nearly fully) covers the image gamut is, as I keep saying: the case where you print using a perceptual mapping.  But you need to define what 'worse' is.  It may look absolutely fine and you may be entirely delighted with it.  By 'worse' I mean that the colors will have been shifted more, so, for example, the match to the display image (not the soft-proofed image as this will also have the shifted colors) will be worse.
Again, while perhaps theoretically true, but not demonstrable.  It just doesn't happen - we're not cramming the entire ppRGB space into an output space. The mapping is relative to the distance the colors are out of gamut which is rarely that extreme.  And I think most photographers don't use perceptual that often ... guessing I use it only about 5% of the time. And when I do, starting over in  a smaller space which may contain the gamut of the file doesn't equate in a better image  (tried that a few times over the years as well and I've never seen a visual difference)

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  If your objective is to get a print that as closely as possible matches your monitor (not soft-proofed) image, then you may see greater differences with the large working spaces.
Why would that be my goal?    My goal is a perfect print, and I want the display help me arrive there and provide some predictability and ease the workflow.  But a perfect match to a display is never what I'm after. If my print has a little more "color" in a region because the printer gamut is larger there, I've never seen that cause a problem, and I certainly don't want to throw that data away. Now certainly there are some workflows that have other priorities, but my final judgement/edits/tweaks come from examining prints.  Now I don't have to do much tweaking from the initial test print too often, so the system is working nicely.

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I fully accept and always have that using too small a workspace is even worse ... because then you will almost certainly get clipped colors if your image has saturated colors.  Just to be clear.
Yes we know that. And we've never disagreed that using a smaller space if it will contain all the data and modified data doesn't work as well. And when you mentioned "clipped" colors because they are saturated, the colors we are talking about are extremely important because they help you pull open the shadows.  To me that's the most important aspect of what the current printers offer in expanded gamut.  But you can't do that in aRGB.

 The discussion really boils down to two points. From your first post "If you go for a larger working space like ProPhoto you are really asking for trouble (this is entirely my opinion!)".  I don't believe that opinion is shared by many, and I believe is very misleading.  Anyone who will get into trouble with this workflow with modern raw processors and photoshop will get into trouble anyway.  Secondly, whether or not using ppRGB for files which can be contained in smaller spaces is detrimental to the final image, and working in a space closer to the size of the data will deliver a better result (print).  And perhaps while theoretically true, I"ve never seen anyone be able to demonstrate this.  This second point is really where the main discussion has ensued, and I'm not sure why we should accept your opinion (and perhaps that of a few others) when empirically through printing hundreds of images over the years we've never seen any evidence to support the idea.

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As for proving my point, as Andrew is insisting I do :), no, I'm not interested in taking this any further. 

Agreed no point in taking this any further.  Great you trust logic, but logic and even scientific evidence don't always equate to something that matters.  That's where I think we disagree the most, you believe that this is an issue, where most would feel it's not anything to be concerned with because you just can't see the difference. As far as demonstrating it, you are the one who is challenging current thinking and practice and telling others your way is better, wanting people to accept it on "logic" and some theoretical math.  But if you can't show it, then is it really an issue to be concerned with?  Maybe it is there, but if it were a problem, you would think it would confound and frustrate many people over the years that would cause us to rethink our workflows (as using ppRGB instead of theses other spaces did at one point in time).

If there were an easy way to do it, maybe it would be worth doing (still doubting it).  But I just can't see any reason to muck up the workflow trying to figure out if my image needs to be in ppRGB, or whether sRGB or aRGB might be enough. No point, because just staying in ppRGB isn't a problem.
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John Hollenberg

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Re: ipf8400 gamut
« Reply #53 on: September 23, 2014, 11:53:39 pm »

After reading through this thread here is my conclusion:

1) It is theoretically possible that using a color space that is too large may result in a print that is suboptimal compared to using a color space that is the right size
2) Experienced printers have not been able to find a practical example of this in spite of looking for it
3) The poster advancing the theory is not interested in finding even a single image where the differences in prints support his hypothesis, making one wonder whether he would be able to do it
4) Using a working color space that is smaller than the gamut of the output device (in this case, the printer) will definitely cause important color information to be lost, and for images of nature it is easy to find such cases (e.g., poppies)

Conclusion: I will continue using Prophoto as my working color space for all images until at least one example is provided that a better print (i.e., truer to the colors in the image) comes from using a smaller color space.

PS I like theory as much as the next guy, but we are talking about perceptible visual differences in prints as the gold standard.  If a discerning eye can't see it, then it really doesn't matter.
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Re: ipf8400 gamut
« Reply #54 on: September 24, 2014, 01:36:00 am »

If there were an easy way to do it, maybe it would be worth doing (still doubting it).  But I just can't see any reason to muck up the workflow trying to figure out if my image needs to be in ppRGB, or whether sRGB or aRGB might be enough. No point, because just staying in ppRGB isn't a problem.

And this is the crux of the matter...is there a "better" wide gamut RGB working space? Maybe, but if you are using ACR/LR, you're already working in ProPhoto RGB (albeit with gamma 1). Is it worth going from PP RGB into some other working space? If you are trying to eeek out the most of your working space, maybe, but, what does the image look like? Are there colors that are critical for the image to succeed that will be better handled by ARGB or Beta RGB? Really? Is it worth turning your workflow upside down (meaning breaking your workflow in order to eeek out some additional color rendering based on various perceptual rendering intent capabilities)?

Penny wise, pound foolish...what you think you might be gaining is wasted by spending unnecessary steps in the workflow in order to gain theoretical improvements that may or may not show up in the final print.

You have a large gamut output device...you have a large gamut capture device. It behooves you to use a working space that contains both...PP RGB does and has been chosen by one of the smartest imaging scientists I know as the working space of ACR & LR–Thomas Knoll. So far, none of the arguments have risen to the level to making me willing to change my workflow. It's all fools gold...
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Robert Ardill

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Re: ipf8400 gamut
« Reply #55 on: September 24, 2014, 02:37:25 am »

Such as? The question of the day which remains unanswered.   Not seeing that, not with my images sorry. I know you may feel this is true based on what you've read and that's fine. It's not what I'm seeing. And again, the proof is in the print. If I don't like the Perceptual mapping, I don't use it. Simple as that.  That's subjective but then so is a color print.

Agreed - I also almost never use perceptual for the very reason that it causes color shifts (the whole reason behind it is to maintain the relationship between colors, not to retain the Lab values of the colors).  I always use Relative unless Perceptual really does look better, which is rare but some canned profiles I've used with fine art matte seem better in Perceptual.  At any rate, to the extent possible it is really much better not to print images that are OOG for our printer/paper:  the biggest issue with very wide gamut working spaces is that it makes it relatively easy to go OOG (for the print), without realizing it because we can't see the OOG on our monitors without turning gamut warning on (which is something I always do, btw); smaller working spaces limit the extent to which we can inadvertently go OOG, as well as making the job of the CMS easier.

This brings us to another point which has been hijacked by the Perceptual issue: and that is what happens when you have a large gamut image that is mapped using Relative to the smaller print gamut: well, as you demonstrated in your video, Andrew, what you get is clipping, flattening and banding.  I hope that you will agree especially as this is really the main point of your video.

So, here is a test which is a much fairer test (even though it is absurd to be scrunching an image with such a wide gamut into a small sRGB gamut):

 Right-click to view full size.

What I've done here is first of all to convert the image to the destination print space using a perceptual mapping (relative would be fine too).  What this does is limit the gamut to the destination (no disagreements I hope!).  I then converted the left copy back to ProPhoto and the right image to sRGB using a perceptual mapping.  So the ProPhoto image should have essentially little change from the print mapped image as it has a much wider color space, whereas the sRGB image will be scrunched down somewhat.  

I think you will see that there is now very little difference between the images, even though one is back in ProPhoto and the other now in sRGB.  The main reason why there is such a huge difference between these images and the ones on Andrew's video ... is NOT the conversion to the print space: it is that, by doing it this way, I have avoided the Relative Colorimetric head-chopping act of converting the image from ProPhoto to sRGB.

OK, I know, I know ... you're going to say 'show it to me on print'.  Well, I can't, but here they are soft-proofed using Relative Colorimetric, BPC, Simulate Paper:



Not a hell of a lot in the difference, is there?

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You've got this idea about smaller than ProPhoto gamut working space being beneficial and that may be true, but you've failed to provide a way to backup that claim I can see. You seem somewhat more interested in gamut maps and what authors of color management software say than what the output looks like which is fine. But I'm a photographer first, a color geek 2nd and what the print or display looks like takes the prize before any gamut map. You kind of remind me of the photographer more interested in the image histogram than the image itself in terms of evaluating image quality. And unless the gamut plotter you use acts like ColorThink, I don't trust it at all for this evaluation. But even if it does behave the same way, the rubber hits the road when solid pixels map in context and we view them, either on-screen or on a print. So if you have some basis to back up your ideas that we can use to evaluate what you're suggesting, and do so with images we can look at, you're entitled to that opinion but it may not be shared by others!  I trust what I can see to judge the qualities of an image workflow and you haven’t provided any means to do that.  You don't have to know squat about rendering intents or color management to conduct my test and see the differences. That's where what you and I propose differ. It's not necessary to understand anything about what happens under the hood, just take one file, convert to another working space and make two prints. View, decide what looks best. Easy breazy. That's all we're asking of you but at this point, I don't think that's going to happen so let's move on.

The problem with what you suggest, Andrew, is that every image is different, so to prove your point by printing is very time-consuming and expensive ... and seeing as how we're on different sides of the Atlantic it makes it difficult for us to view the same prints.  But returning to the color geek v. real life photographer: the reason I became interested in looking to see what is under the hood is that when I started off I had no idea about color management and I made very stupid mistakes - like, for example, using the very widest color space I could get because bigger naturally seemed better ... only to find that my prints were way more muted than they should have been, or the colors were just wrong.  So you then go through the process of trying to figure out: is it the printer, the monitor, the image ... what's going wrong?  And you find out that if you have an sRGB monitor (which I did at the time) and you edit in ProPhoto ... well the image might look great on screen (after all, you've edited it so that it does look fine) ... but there are bunches of colors there you can't see.  When you then print you're then at the mercy of the CMS - and what can it do but the best of a bad situation?

As for the Gamut Plotter I use (it is a lot more than just a gamut plotter), it's GamutVision from Imatest.  It has features that Chromix does not and vice versa, but Imatest is a serious company in the image testing business, as I'm sure you know, so I think it's reasonable to assume that GamutVision is reasonably reliable.

Robert
« Last Edit: September 24, 2014, 02:47:05 am by Robert Ardill »
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Re: ipf8400 gamut
« Reply #56 on: September 24, 2014, 04:32:46 am »

As I mentioned, been there done that.  And I could not demonstrate it. It's great you trust "logic", but logic doesn't always equate to reality.  And I don't know why it's up to anyone else to demonstrate your point of view (and in fact I don't think it can be done ... well, never say never but if so the circumstances would probably be extremely rare and unique.)

I really don't care if you or anyone else attempts to prove or disprove me ... it's just that Andrew keeps on at me to PROVE my point.  I feel no need to do so beyond what I've already done.  I also agree with you that demonstrating the issues with prints is very difficult ... which is why it's a very good idea to understand what is happening under the hood.

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Well, the reasons the for the existence of sRGB and AdobeRGB have nothing to do with a  photographers workflow and providing an "intermediate option.  They were created for specific purposes that have nothing to do with a photographers workflow and current technology. (as opposed to ProPhotoRGB which was specially created for digital capture/printing technologies to be future proof, so the main goal was  to try and make sure all naturally occurring colors could be defined).

Funny you should say that when Adobe RGB was created by Adobe, specifically to address photographic needs that went beyond the (hardware-driven) sRGB space.

And you should know, surely, that ProPhoto does NOT define all naturally occurring colors (or more correctly, all colors that we can see).  Here is a simple demonstration of that:



ProPhoto is the triangle, the horseshoe is the typical extent of human vision.  ProPhoto not only does not cover all of human vision, but it goes beyond to what (probably) no-one can see.  The reason for it is to cover a large chunk of human vision ... but why did they stop where they did?  Why not go the whole hog and cover the whole of human vision, accepting that with a triangular gamut this will (as does ProPhoto) include colors outside our vision?  Seems to me that if you want big, ProPhoto just isn't big enough!


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The mapping is relative to the distance the colors are out of gamut which is rarely that extreme.

Well, with Perceptual the mapping is relative to the gamuts (unless the profile maker cheats a bit and does a mix of relative/perceptual).  

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And I think most photographers don't use perceptual that often ... guessing I use it only about 5% of the time. And when I do, starting over in  a smaller space which may contain the gamut of the file doesn't equate in a better image  (tried that a few times over the years as well and I've never seen a visual difference)

Your images are probably not very saturated so you should be fine (you will be making very limited use of the additional gamut in ProPhoto).  But there are photographers (or graphic designers and painters) who do use very saturated colors ... and for these perceptual may be better as it does attempt to preserve the relationship between the colors, whereas relative will clip the OOG colors (which may look much worse).

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But a perfect match to a display is never what I'm after.

Admittedly a perfect match is pretty much impossible because we are dealing with fundamentally different devices.  However the goal should surely be to see what you are going to print and for your print to be as close as possible to what you saw.  In my case I can say that (having spent quite some time coming to grips with it) that I can get an almost perfect match between my prints and my display.  It's a revelation when you achieve that because you can then be confident that when you hit the button you'll get the print you want.

It is of course true that this matching will only be correct for a particular viewing condition.  However, fortunately our eyes adapt to different lighting and compensate to a large extent automatically, so on the whole if the print looks good under one light it will most likely look good under another.

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And when you mentioned "clipped" colors because they are saturated, the colors we are talking about are extremely important because they help you pull open the shadows.  To me that's the most important aspect of what the current printers offer in expanded gamut.  But you can't do that in aRGB.

Of course if you've clipped the colors you aren't going to get them back!  If you want to pull open the shadows you should absolutely do this at the raw conversion stage ... don't even wait to have your image in ProPhoto because at that point you've lost data already.

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The discussion really boils down to two points. From your first post "If you go for a larger working space like ProPhoto you are really asking for trouble (this is entirely my opinion!)".  I don't believe that opinion is shared by many, and I believe is very misleading.  Anyone who will get into trouble with this workflow with modern raw processors and photoshop will get into trouble anyway.  Secondly, whether or not using ppRGB for files which can be contained in smaller spaces is detrimental to the final image, and working in a space closer to the size of the data will deliver a better result (print).  And perhaps while theoretically true, I"ve never seen anyone be able to demonstrate this.  This second point is really where the main discussion has ensued, and I'm not sure why we should accept your opinion (and perhaps that of a few others) when empirically through printing hundreds of images over the years we've never seen any evidence to support the idea.

If you know what you're doing then ProPhoto is fine.  My original response was to this post by mstevensphoto who asked: "Hi all, I'm reading my literature and see that the ipf8400 has a 5-6% wider gamut but I don't see any comparison of the   printer to the sRGB space. Does anyone know if it is able to print more colors than are in srgb (thus making me work in adobe98) or how the two line up?"  With all due respect to mstevensphoto, he, like a great many photographers, clearly doesn't know much about working spaces or he would not have asked the question.  The fact is that the iPF6400 has a much bigger space than Adobe RGB and also a much smaller space than sRGB ... depending on what papers you print on and what part of the image you are looking at (for example, the printer doesn't come close to sRGB at the dark end on a matte paper).

So, if you are responding to someone who doesn't really understand the pros and cons of workspaces ... would you recommend ProPhoto?  Not me.  Or at least if I did I would accompany the recommendation with information on what to do to make sure that he doesn't unknowingly ruin his images by going way out of gamut.

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Agreed no point in taking this any further.  Great you trust logic, but logic and even scientific evidence don't always equate to something that matters.  

Are you a member of the Flat Earth Society? :)

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That's where I think we disagree the most, you believe that this is an issue, where most would feel it's not anything to be concerned with because you just can't see the difference.

All you can say here is that YOU can't see the difference.  Our eyes vary hugely in their ability to detect subtle color differences.

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As far as demonstrating it, you are the one who is challenging current thinking and practice and telling others your way is better, wanting people to accept it on "logic" and some theoretical math.  

Whose 'current thinking and practice', and is this the best practise?  Andrew's, yes ... who else who considers themselves experts in color management?  Bruce Linbloom, maybe (makes you wonder why he created Beta RGB! http://www.brucelindbloom.com/index.html?BetaRGB.html).

I don't want people to accept what I say.  I'm a scientist by training and I firmly believe that we should all come to our own conclusions based on the evidence we are presented with.  And yes, I do think that logic and maths is one of the best ways of cutting through the bullshit.  It's not like we're talking theoretical physics and sub-atomic particles here ... we are talking in the realms of 2+2=4, and there is no arguing with CMS mapping algorithms: these are computer programs and they are cast in concrete, so to speak.  As Jeff Schewe said in one of his post or essays or something, GIGO! Garbage in Garbage Out.  If you send garbage to your printer, expect a less than optimal result.  Looking at the profile and seeing how well this encompasses your image gamut is one very good test of the integrity of what you will be sending to your printer.

The problem we have is that we don't know (at least I don't) XRite's algorithms (for example).  However we can totally know ArgyllCMS's algorithms because Graham Gill has very generously made his software open-source.  I think few people would argue that his algorithms are inferior to XRite's (unless the person is an XRite employee, perhaps).  On the contrary, a bit like RawTherapee, ArgyllCMS has a wealth of options that are simply not available with XRite and which, for example, give us the possibility of generating image-specific profiles.  There are very few systems out there at the moment that have that level of sophistication.

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But if you can't show it, then is it really an issue to be concerned with?  Maybe it is there, but if it were a problem, you would think it would confound and frustrate many people over the years that would cause us to rethink our workflows (as using ppRGB instead of theses other spaces did at one point in time).

If there were an easy way to do it, maybe it would be worth doing (still doubting it).  But I just can't see any reason to muck up the workflow trying to figure out if my image needs to be in ppRGB, or whether sRGB or aRGB might be enough. No point, because just staying in ppRGB isn't a problem.

I think I have shown that there is an issue, or at least a potential one.  A very simple case was very nicely demonstrated by Andrew when he (very unkindly) did a relative colorimetric conversion of a ProPhoto image to sRGB (in his video): he chopped the top off the poor image's head and ended up with something that looked as flat as a pancake.  Where he went wrong is in blaming sRGB for that: the fault was his, not sRGB's.

If you're happy with ppRGB then totally fine ... I have ABSOLUTELY NO problem with that.  I am NOT trying to convince you, or anyone, else to change.  I am just attempting to correct what I think is misinformation.

Robert
« Last Edit: September 24, 2014, 04:45:32 am by Robert Ardill »
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Re: ipf8400 gamut
« Reply #57 on: September 24, 2014, 05:10:26 am »

After reading through this thread here is my conclusion:

1) It is theoretically possible that using a color space that is too large may result in a print that is suboptimal compared to using a color space that is the right size
2) Experienced printers have not been able to find a practical example of this in spite of looking for it
3) The poster advancing the theory is not interested in finding even a single image where the differences in prints support his hypothesis, making one wonder whether he would be able to do it
4) Using a working color space that is smaller than the gamut of the output device (in this case, the printer) will definitely cause important color information to be lost, and for images of nature it is easy to find such cases (e.g., poppies)

Conclusion: I will continue using Prophoto as my working color space for all images until at least one example is provided that a better print (i.e., truer to the colors in the image) comes from using a smaller color space.

PS I like theory as much as the next guy, but we are talking about perceptible visual differences in prints as the gold standard.  If a discerning eye can't see it, then it really doesn't matter.

2) That's a very generalized and unfounded statement.  Could you give us a breakdown of how many experienced printers (and who these are) who've done this massive investigation?  And could we see their published results please?
3) I've given a demonstration in one of my earlier posts where I showed what happens when you convert an image from sRGB to ProPhoto and then convert both of these to the print output.  What more do you want?  If you think it's easy to prove by printing that larger color spaces causes more shifting when using a perceptual mapping (especially when we are all separated by thousands of kilometers) ... well, think again.
4) Totally untrue.  Using a working space that is smaller than the gamut of the image will result in a loss of colors, using a working space that is smaller than the printer's gamut will result in no loss of colors.  Yes, if your image has poppies then I would recommend ProPhoto as a working space (but make sure you turn on your printer-space gamut warning!!).

Showing ONE example of an image that suffers from too large a working space isn't going to change your views ... you will want another and another and another, and I for one do not have the time or inclination to do this work for you since I do not need this sort of proof myself.  If you're happy with your workflow then that's fine, really, I mean it ... I'm not a color management evangelist like Andrew and I'm not trying to convince anyone that they should change their working practices or that they should agree with me.  But I will certainly defend myself and if I think there is misinformation being broadcast then I won't be too shy to point it out, as I have here.

Robert
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Re: ipf8400 gamut
« Reply #58 on: September 24, 2014, 05:35:54 am »

And this is the crux of the matter...is there a "better" wide gamut RGB working space? Maybe, but if you are using ACR/LR, you're already working in ProPhoto RGB (albeit with gamma 1). Is it worth going from PP RGB into some other working space? If you are trying to eeek out the most of your working space, maybe, but, what does the image look like? Are there colors that are critical for the image to succeed that will be better handled by ARGB or Beta RGB? Really? Is it worth turning your workflow upside down (meaning breaking your workflow in order to eeek out some additional color rendering based on various perceptual rendering intent capabilities)?

Penny wise, pound foolish...what you think you might be gaining is wasted by spending unnecessary steps in the workflow in order to gain theoretical improvements that may or may not show up in the final print.

You have a large gamut output device...you have a large gamut capture device. It behooves you to use a working space that contains both...PP RGB does and has been chosen by one of the smartest imaging scientists I know as the working space of ACR & LR–Thomas Knoll. So far, none of the arguments have risen to the level to making me willing to change my workflow. It's all fools gold...

Well, you're not working in ProPhoto RGB in Lightroom: you're working on the raw data.  ProPhoto is being used to render the image, but we do have the choice of workspaces when we export the image or open it into Photoshop.  And as you well know, none of our monitors can display ProPhoto, so how can we be working on something that we can't see?  Lightroom wouldn't have soft-proofing and gamut warnings if we could.  The reason for using ProPhoto in Lightroom is obvious, as I've already pointed out: the working space has to cover all possible images, past and future, from all possible photographers, covering all possible subjects, for all possible output devices.  Only a large working space can hope to do that (and ProPhoto is not large enough to do so, as you know).

A good workflow will ALWAYS check for OOG.  If you do not then you are not following good practice and as a result you will at some point hit some ugly results.  Once you've checked for OOG you already know the gamut extent of your image.  The choice of working space is then trivial.  It might add a few seconds to your work, but compared to the time you spend editing the image it's NOTHING.  Just pick a working space that comfortably contains your image ... what's so hard about that?

Eking out the last drop of quality out of images is really important to a lot of us.  Whether that is composition, capture technique, sharpening or detail recovery, processing, printing ... they are all important.  It may be that choosing a very large working space as your standard working space is pretty OK - if you are careful and know what you are doing.  Andrew himself has said that the bitch is the monitor: it can't display saturated colors that can be captured and printed.  So, we have a choice: we accept that we won't be able to see some of the colors in the image until we print so that we may well then need to do at least one proof print, and perhaps several; or we try to keep things within the monitor gamut so that we can have a high degree of confidence that we will only need to do one print, accepting that we will for some images sacrifice some colors; or we do both depending on the image.  If I'm going to print poppies then I will use ProPhoto and accept that I may have to do a couple of prints before I get the colors right and get rid of the banding; if I'm going to print a general landscape (that almost always falls well withing Adobe RGB) then I'll use Adobe RGB.  If I was a portrait photographer then I would definitely use Adobe RGB (unless the bride had a poppy in her hair :)).

So by all means Jeff, do stick to ProPhoto: it seems to be serving you well and I think you do know all about OOG etc., so you won't be doing stupid things with your image.

Robert
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Re: ipf8400 gamut
« Reply #59 on: September 24, 2014, 06:20:30 am »

Funny you should say that when Adobe RGB was created by Adobe, specifically to address photographic needs that went beyond the (hardware-driven) sRGB space.

Funny you should think that since Adobe RGB (1998) was a typo based on preliminary specs of SMPTE 240M (a proposed editing space for HD video). Seems Mark Hamburg was surfing the web one day for RGB editing spaces and found the spec. Unfortunately, there were typos in two the the color coordinates listed. Course, Adobe didn't find that out till AFTER Photoshop 5 actually shipped. So, Adobe changed the the name from SMPTE 240M to Adobe RGB (1998).

See, Adobe didn't create the color space to address photographic needs...it created Adobe RGB (1998) by accident.

On the other hand, PP RGB was created by Kodak after a lots of research specifically meant to address the needs of editing photographs.

See the folly here?
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