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lester_wareham

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« on: August 04, 2005, 04:26:37 am »

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Try this. -- Pick a file with a wide color range with some colors known to be out of gamut. If the file is not already in ProPhoto then ďAssign itĒ to ProPhoto and do a soft proof using the printer profile you plan to use and turn on Gamut Warning. Observe. Now Assign the same file to MatchColor. Much less out of gamut colors.
Yes I have tried that and what would have clipped with AdobeRGB was clipping in ProPhoto anyway (Epson 1290 Premium Photo Glossy and a bit less in heavy matt).

SO not an issue with the current printer. I guess it may be an issue for future printers.

Thanks for the links everyone, I will study these.
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Mark D Segal

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« Reply #1 on: August 05, 2005, 07:57:49 am »

Jonathan, from my posts above - based on what I've heard at seminars and read about this matter we're on the same wave length about using proPhoto, but the thing that really intrigues me is how relatively small are the color gamuts of our printers †- seemingly ALMOST to the point that differences in gamut shape could still have some effect for some hues, but perhaps with very low probability of occurrence - oh, and by the way, next time I need expert advice on the anatomy of a weasel I'll know where to turn.
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Mark D Segal (formerly MarkDS)
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Hermie

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« Reply #2 on: August 05, 2005, 03:08:04 pm »

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Only working in Adobe1998 you have less room to get lost in compared to ProPhoto.

Why are you so scared to get lost Paul ;-) ? You probably didn't get lost in aRGB and you won't in ProPhoto (as long as you edit sensibly, which of course applies to aRGB too).

I also would like to add 2 comments that Bruce Fraser wrote on the Adobe forums.

Comment 1:
- adds info to DigiDog's comment "As for the idea of a wider space only being useful for very saturated colors, thereís more to it than that"
- addresses clipping

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"If you look at RGB matrix spaces (i.e., those defined by a white point, primaries, and gamma-defined tone curves) in a 3D lab plot like those offered by the ColorSync utility or Steve Upton's indispensible ColorThink, you'll see that they all reach their maximum saturation at a fairly high luminance level. The gamut narrows dramatically at lower luminances, tapering to a point at black.

Print spaces plotted the same way have a different shape, where maximum saturation is acheived at lower luminance levels. (In an RGB space, you make more saturation by adding light, on a printer you make more saturation by adding ink, so this makes sense.)

So an RGB matrix space that has a wide enough gamut at lower luminances to hold the printer gamut has to have extremely wide primaries that may not represent anything that's physically possible. Obviously, that leads to the space containing non-realizable colors. It's the trade-off you make when you want to create an RGB matrix space that contains all the realizable colors from your printer, and that's why ProPhoto is so large.

Then there's the question of clipping. It's not at all hard to capture colors that are outside Adobe RGB. Many of the dark greens and yellows that are prevalent in nature are outside Adobe RGB, and if you convert to Adobe RGB, or a smaller space, gradations of those colors get clipped to solid blobs. There's already been at least one such problem image posted on this forum. So the advantage of ProPhoto isn't about retaining all those out-of-gamut colors per se, it's about maintaining the distinctions between them, so that you can map them into printable space as gradations rather than blobs."

Comment 2 on bit depth:

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"I know of less than a handful of capture devices that claim to capture a full 16 bits, and I'm skeptical about at least half of them.

Photoshop's 16-bit implementation gives you 32,769 levels (0-32,768) and the topic as to why that's the case has been done to death here and elsewhere.

I've been using that implementation in ProPhoto RGB for about seven years now, with a variety of capture devices ranging from 10-bit to 14-bit capture. You can make any file fall apart if you push it hard enough, but 12-bit capture devices are more than capable of withstanding the rigors of ProPhoto RGB. (I'm careful not to advocate it, but I've been known to edit 8-bit files in ProPhoto without anything terrible happening....)"

Herman
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digitaldog

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« Reply #3 on: August 06, 2005, 01:31:34 pm »

-->To comment on my question: †Yes, those silent assumptions exist, but ... ďThat is closely held secret by GMB. Likewise with Monaco/X-Rite. The color space assumptions in ProfileMaker differ based on the parameters used when the profiles are construed.Ē (by Ethan Hansen).
If anyone knows more, please post.

By the time an output profile ďgetsĒ data, itís gone through the PCS and is in LAB. So if Iím understanding where youíre coming from, I'd say again that the output profile has no real idea what the incoming data is as far as the original RGB color space (sRGB, ProPhoto etc). The conversion takes place like this; working space (letís say sRGB for one file, ProPhoto for another) converted to LAB by the CMM. Thatís the device independent color space used by the PCS. LAB to output profile now takes place. So the output profile has no idea if the LAB data came specifically from sRGB or ProPhoto RGB. Yes, the data is different for obvious reasons and yes, with some imagery, the smaller color space CAN be somewhat beneficial. But the CMS as yet has no provisions to know this. The output profile is simply getting LAB values to work with.

The opposite is the case with device links. Iíve never seen one that works RGB to RGB but havenít really looked or tried to build an RGB device profile since I donít know what that would bring to the party (and Photoshop and many other ICC aware applications canít handle Device Links). But with a device link, the advantage is you can produce a CMYK to CMYK conversion without a trip into LAB; thereís no PCS in the process. This is useful when doing CMYK to CMYK conversions because you can retain the black generation. When you do this using ICC profiles, thereís a trip into LAB, the black generation is hosed. So with device links, thereís a direct relationship between source and destination but for a specific reason.

-->Todayís printer resp. printer profiles are not prepared for the case the we come along with a heavy-loaded file in ProPhotoRGB.

I donít see it that way. It really doesnít matter. The printer has a fixed gamut. The original data has a fixed gamut. You want (or maybe you donít want but I do want) all the color the capture device was capable of producing. Printer A may be able to use 80%, printer B may only be able to use 60%. Thatís just the facts of life and you either have a source space that contains the colors or you donít. This isnít going to affect the printer; a smaller source isnít going to allow you do reproduce any more colors (only less). So I donít see why originally containing less colors versus more is any way a factor here.

-->The mantra "use ProPhotoRGB to avoid channel clippingď is akin of self-fulfilling prophecy, because ACR doesnít support any other rendering option (yet). Hence, all the burden of a perceptual de-saturation is imposed either to the operator or to the printer profileÖ.

Thereís only one rendering intent (actually one table, two intents) you can use with matrix profiles (Adobe RGB (1998), ProPhoto etc) and thatís colorimetric. If youíre asking for some kind of protectoral option, I guess thatís reasonable and I donít know enough to say if thatís doable or useful. But the facts are, we have capture devices that can produce a very wide gamut of colors and tones we probably canít output today and maybe never will.

-->Could the industry please kindly sort this out without involving us customers. Not everyone loves to fiddle with the Hue&Sat.-tool or the Channel Mixer to tame out-of-gamut colors.

Out of gamut colors are a fact of life and users need to decide how they wish to handle them. There is no one-size fits all conversion. Thatís why we have different rendering intents, soft proofing and tools like Photoshop to attempt to produce a reproducing on a smaller gamut, lower dynamic range output device to fit our idea of what the image should look like.

Weíve never been able to reproduce the gamut and range of a transparency on print but that didnít stop people from making beautiful representations of the film for years.

-->ďDevices such as digital cameras and printers perform embedded (typically proprietary) perceptual renderings to and from standard color encodings like sRGB.

Iím not sure what that brings to the discussion. I suggest you read the white paper there (which I co-authored) which discusses the processes of in camera rendering and encoding.

http://www.color.org/ICC_whi....ics.pdf
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Andrew Rodney
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« Reply #4 on: August 07, 2005, 07:49:18 am »

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Any ďbest practiceĒ how to proceed?
Yes, use Photoshop's softproofing to see what the heck the image will look like when printed, pick the best rendering intent for the image and under softproofing, adjust the image to achieve the results you want.
Jeff,

Two questions please; one technical and one workflow-related.

The Color Range tool offers an option to select ďOut Of GamutĒ colors. †Which target profile does it refer to? †It seems that the selection differs considerably from the SoftProof / out-of-gamut marks.


After youíve processed a file through Camera Raw (ProPhotoRGB, 16 bit), do you instantly enable the SoftProof to the printer/media profile, or is there an editing step in-between based on ďnormalĒ presentation on screen?

Peter

--
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Mark D Segal

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« Reply #5 on: August 07, 2005, 07:52:14 pm »

pom, of course you're joking.........no way I would let these arcane esoterics deprive me of the benefits of digital.

Peter - fine, the same thing with added detail, but so what? The bottom line is that anyone claiming a significant downside to working in Prophoto color space needs to demonstrate in normal photographic prints that rendering intents have a differentially negative impact on posterization as you move from smaller to larger embedded or working color spaces relative to the (fixed size) output color space. It is not clear in principle and where is the practical real-life evidence?
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Mark D Segal (formerly MarkDS)
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Ray

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« Reply #6 on: August 09, 2005, 09:54:18 pm »

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Iím not sure what you mean ďthe sRGB image required less desaturationĒ.
The sat slider of the PS hue/sat tool required less adjustment to remove all of the grayed-out areas (-68 for sRGB as opposed to -71 for the ARGB image and -62 for PP), all in relation to the Bill Atkinson Prem Gloss profile.
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digitaldog

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« Reply #7 on: August 10, 2005, 12:20:51 pm »

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When you convert (one step), thatís EXACTLY what you get.
Andrew, the softproofing you describe in your last post above is what I have been doing but the phrase I quoted confuses me. I have the softproof set-up the way you say, and to activate it I click "CTRL Y" (Windows XP) which I understand doesn't change anything in the image file - it "simply" renders a monitor image simulating what the printed output will look like - and it does so pretty well. When I click CTRL Y again the simulation disappears. Is this what you mean in the above quote from your post, or do you mean that once I click "PRINT" Photoshop remaps the file data to the output profile for printing (but doesn't retain the remapped data thereafter) or do you mean something else?
No, I was referring to the Gamut Warning option in the same menu that places an ugly gray (by default) mask over out of gamut colors. Thatís not the same as using the Soft Proof with an output profile.
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Andrew Rodney
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Mark D Segal

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« Reply #8 on: August 11, 2005, 08:18:11 am »

Yes Ray, I think we have all been through that stage!!!

I appreciate your observations on predictability of shadow detail using Gamut Warning vs Soft Proof when switching rendering intent. I haven't made this exact comparison, so it will be interesting to see Andrew's comment on this.
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Mark D Segal (formerly MarkDS)
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Ray

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« Reply #9 on: August 14, 2005, 10:04:52 am »

Does anyone use the 'saturation' intent for photos, as opposed to graphics? I find that with some images, perceptual or relcol produces a significant dulling effect with proof colors (on screen) but not with 'saturation'.
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Ray

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« Reply #10 on: August 17, 2005, 09:35:29 am »

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No, that's not the right figure.

2 to the power of 48 is:

281 474 976 710 656
Okay! So it's 281 British billion. That's an even more unrealistic figure. You'd need a Supercomputer and a lot more than Photoshop to handle an image containing all those colors. Does a few billion make any difference in such circumstances, apart from slowing everything to a crawl.
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Ray

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« Reply #11 on: August 17, 2005, 10:36:29 am »

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48 * 300 000 * 300 000 = 4 320 000 000 000 bits = 540 000 000 000 bytes.
Which is approximately 135x the maximum size the TIFF file format can support.  :D
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lester_wareham

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« Reply #12 on: August 03, 2005, 02:49:43 pm »

Is anyone out there using ProPhotoRGB instead of AdobeRGB?

I notice I get a lot less trouble with clipped coloured  highlights in ACR using the wider ProPhoto.

What's the pro's and con's?
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paulbk

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« Reply #13 on: August 04, 2005, 04:05:23 am »

Maybe heís photographing canaries and doesnít mind huge steps in color tone. All you get is 256 tones REGARDLESS of the color space (sRGB, Adobe1998, or ProPhoto). Stretch 256 tones over a large color gamut and banding could be troublesome. Depends on the photo. Further, your eye is more sensitive to color contrast than to absolute color. Your eyes adjust just fine to tungsten light even though the full spectrum colors are way off. A smooth transition in a sunset spectrum or the iridescence in a feather is more pleasing than a blotchy long jump to the next shade.

The academic argument for ProPhoto is far from a decided issue. In the end, itís all in the print.
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paul b. kramarchyk
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« Reply #14 on: August 05, 2005, 08:52:50 am »

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These values are all out-of-gamut, indicated by the exclamation mark, but in relation to the SWOP standard, I assume. But there's a question here that perhaps someone would like to answer.
If you load a soft proof of your output device and then in the Info palette use Proof Colors, you can see the effect on that device (not SWOP).

As for the idea of a wider space only being useful for very saturated colors, thereís more to it than that. Due to the simple shape of these synthetic working spaces, many, especially those that are not real large donít produce a good fit for the output device gamut, especially saturated colors in the output space that are very dark. If you look at good 3D maps, you see this. So in order to fit these colors, the primaries are (like ProPhoto RGB) stretched out to accommodate these areas. Thatís one reason when you look at even a 2D plot of ProPhoto you see the Blue falling outside the CIE chromaticity diagram (itís by design of course).
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Andrew Rodney
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« Reply #15 on: August 05, 2005, 02:30:43 pm »

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and funny enough the same statement (although to a lessor degree) is true for Adobe RGB.

Hermi, You are right! That's exactly my point. Only working in Adobe1998 you have less room to get lost in compared to ProPhoto.
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paul b. kramarchyk
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digitaldog

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« Reply #16 on: August 06, 2005, 02:54:41 pm »

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It seems there is no downside to this.
Offered without comment, since I'm not qualified to comment, but an article discussing potential downsides:

ProPhoto or ConPhoto?

Giles
I actually went to read up on this article and without going to far, found this:

-->All colour spaces of the same bit depth (typically 8 or 16 bit) have the same total number of tones. That is, a bigger colour space does not mean there are more colours in total!

Thatís not really so. This is a fundamental misunderstanding of what a color space is. So Iíll do a quick copy and paste from some text I wrote:

What is a color space? Think of it this way: suppose I supply a recipe for chocolate chip cookies but do not provide the unit for each ingredient in the recipe. The recipe provides each ingredient followed by a number. Without units you canít make the cookies. The numbers alone are not enough information to describe how the cookies that will be produced. Likewise, R78/G103/B23  or C23/M98/M123/K6 is not enough information to reproduce that color.

Going back to the chocolate chip cookie analogy, suppose a color model is a cookie recipe with only three ingredients. I give you this recipe, which simply calls for 1-flour, 8-butter and 2-chocolate chips. You donít have enough information to make the cookies. However if I provide you the recipe with a specific scaleó1 cup of flour, 8 tablespoons of butter, and 2 cups of chocolate chipsóIíve provided the necessary information, the scale, to make a dozen chocolate chip cookies. I can give you the cookie recipe in the metric scale such as liters and grams and you can still makes the same cookies even though the numbers are different. A color space is a color model that has a known reference and scale, in this case primaries (the ingredients) and scale (specific quantities of these ingredients).

Suppose I specify a color as R10/G130/B50 and specify a color reference by saying the color space is Adobe RGB (1998), which defines the scale of the RGB primaries; the color coordinates of this color space. The R10/G130/B50 set of numbers can now reproduce a color by anyone with the proper tools since the reference and scale have been defined. Different RGB color spaces use a different scale of red, green, and blue primaries. Adobe RGB (1998) and sRGB  are different color spaces, however both are based on the RGB color model using RGB primaries. Although each color space uses the same three primary ingredients (R, G, and , the specific colorimetric scale of each color space is different. The maximum of red, green, and blue are more saturated in the Adobe RGB (1998) color space than the sRGB color space. Even though R0/G255/B0 is the greenest green ingredient in both Adobe RGB (1998) and sRGB, knowing that the scale is different in both color spaces explains why this green value is more saturated in Adobe RGB (1998). This also illustrates how R0/G255/B0 alone canít tell us what green.

An ICC profile simply defines this scale and gives the numbers a meaning allowing us to reproduce the color using something far more concrete than using the English word "Green" or a set of numbers which alone is far too ambiguous to produce a specific color appearance.

-----

So going back to ďThat is, a bigger colour space does not mean there are more colours in totalĒ the issue here is saturation of the primary colors (RGB in this case). Yes, R255 in sRGB and ProPhoto RGB share the same number but most certainly not the same scale.
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Andrew Rodney
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« Reply #17 on: August 07, 2005, 07:41:38 am »

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As far as I have been able to parse it, this whole discussion about whether or not it is useful to work in ProPhoto color space so far boils down to two propositions: (a) if Prophoto includes - but ARGB98 excludes - values that current and future generations of printers can reproduce, we should retain those values because they will improve printed image quality; ( as long as we work with 16 bit data, there is very little risk that Photoshop's shakedown of out of (printer) gamut colors will produce any noticeable banding.
Mark,

Referring to point (b.), there are two different mechanisms involved:

Posterization is supported by large spaces with high gamma at low bit depth. †For me, itís a non-issue with ProPhotoRGB at 16-12 bit/ch.

Posterization is a real-world threat (IMO), when you convert a large space such as ProPhotoRGB (including rich colors) to a printer/media profile. †All the color space volume in-between the source and the target space is collapsed on surface of the latter one. †Itís often easily obvious from the print that exactly those out-of-gamut colors why we like to use a large working space have lost details.

Therefore it seems to be required to edit & de-saturate said out-of-colors by hand ďintoĒ the printer/media space.

Peter

--
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Ray

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« Reply #18 on: August 08, 2005, 12:32:02 am »

The last time I tried to do some comparison print tests between perceptual and relative colorimetric with an image with out of gamut colors, I couldn't see any differences. The explanataion at the time was (about a couple of years ago) that unless the paper/printer profile you are using addressed such issues when it was built, then you won't see any difference.

My general feeling is, there's a lot of stuff that's supposed to have an effect in theory, but in practice the effect can be either insignificant or completely dwarfed by other greater influences.

That's why it's necessary to test things for yourself. Don't take anything on trust  :) .
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digitaldog

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« Reply #19 on: August 09, 2005, 09:40:00 pm »

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Brighter (more saturated, or perhaps more intense is the right word) on screen immediately after assigning the 3 profiles, but also after applying proof setup/simulater paper white etc and reducing gamut for all 3. The sRGB and ARGB rainbows are dowdy by comparison.

If the numbers are the same, it would seem the reason why the ProPhoto image did not require the same degree of desaturation as the ARGB image (to bring them both within gamut) is a result of the Premium Glossy paper's capacity to handle at least some of the greater saturation of ProPhoto. Does that make sense?

The surprise is, the sRGB image required less desaturation to bring it within gamut than did ARGB. It would make more sense if this was the other way round.
Assigning the profiles would of course change the color appearance from prior to the assignment. The soft proof would look different as well. When you Assign a profile, you change the meaning of the numbers so Photoshop updates the preview based on those new definitions (even though the numbers are the same).

Iím not sure what you mean ďthe sRGB image required less desaturationĒ.
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Andrew Rodney
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