ipf8400 gamut

[mstevensphoto]

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?

[Czornyj]

Sure, even AdobeRGB wastes some of iPFx400 colours

[Robert Ardill]

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?

Well actually you need to be careful as the gamut will be wider in places and smaller in others.  For example, even with high gloss papers you won't get the blacks that are present in sRGB.  On matte papers you will definitely not get anywhere near the full sRGB gamut, especially in saturated reds, yellow, purples.

Here is an example of a gamut on an HP Z3100 (which won't be much different to the iPF8400) on Canson Hi Gloss Premium (as good a paper as you can get), compared to sRGB (sRGB is the wireframe):



As you can see, the gamut volumes are about the same - but the printer is much wider in the saturated cyans, but significantly smaller in the saturated greens, blues and purples.

Robert

[mstevensphoto]

given that info and focusing on differences one can *actually see*, which colorspace would you work in? I DO have a monitor capable of working in adobe98.

[Robert Ardill]

given that info and focusing on differences one can *actually see*, which colorspace would you work in? I DO have a monitor capable of working in adobe98.

We had a long discussion about this here: http://www.luminous-landscape.com/forum/index.php?topic=91514.0.  Your printer gamut will be larger than both Adobe RGB and sRGB in places, and smaller in others.  If you use sRGB then you really will be limiting the printer's potential a lot, with Adobe RGB much less. The advantage of Adobe RGB is that your monitor will be close to it, so if everything is set up correctly you will be in a reasonable wysiwyg situation.

If you go for a larger working space like ProPhoto you are really asking for trouble (this is entirely my opinion!) as there will be large areas of color that you cannot see on your monitor and which you will not be able to print either.  An intermediate color space like Beta RGB is better as it will pretty well fully encompass both your monitor and printer gamuts - but the problem with it is that again it will contain colors that cannot be seen on your monitor.

So it really depends on your images.  If you're trying to squeeze the last bit of saturated colors out of your printer then I would suggest Beta RGB.  If you're happy to live without a few of the most saturated colors, then I would go for Adobe RGB, as I mostly do.

That way you can turn on Gamut Warning in Lightroom or Photoshop and you will be able to see what colors your printer will not be able to print.  Then it will be up to what rendering intent you use to determine how these out-of-gamut colors are handled.

Robert

[Wayne Fox]

If you go for a larger working space like ProPhoto you are really asking for trouble (this is entirely my opinion!) as there will be large areas of color that you cannot see on your monitor and which you will not be able to print either.  

A common misconception.  In fact colors used in the working space are never seen on a monitor.  Just because a monitor is "adobeRGB" only means it gamut is similar to AdobeRGB, but that doesn't mean you use aRGB as the profile for the display.  So the colors in an image are always converted via a profile to the device space.

Spaces such as sRGB, AdobeRGB and ProPhotoRGB are theoretical spaces that are used as containers.  If your container is smaller than the colors in the image, then the colors are clipped into that working space (and lost).  If the colors exceed the device space, the profile is designed to handle that in  a way the preserves the visual relationship of colors ... this is what the monitor profile is doing.  WYSIWIG doesn't mean exact match, it's about a visual match, and visually matching is more about relationships of colors and tones, not exact numbers. Devices with remarkable different spaces can still look visually very similar.

Since most high end printers  exceed sRGB, as well as AdobeRGB in some colors, using either of these as your working space means you will clip and lose colors (forever).  If printers or other output devices come along that increase the colors, won't do you any good.

A working space is nothing magic, and it really doesn't matter that it's too large. It's just the bucket that holds the data and can be used by the CMS as the base for the conversions.  The only caveat is an 8 bit file really can't manage very well with all the colors available in ProPhotoRGB.  Using ProPhotoRGB with an 8 bit file is asking for trouble.

It seems many get hung up about gamuts and how large they are and how they compare and seem to draw some conclusions about matching "gamuts" in the color management process.

Adobe Lightroom is a perfect example of how it all can work seamlessly and without much user involvement ... a good display profile built to match the output profile, everything in the middle handled internally (in a version of ProPhotoRGB 16bit).  Same thing works equally well with Photoshop if you just trust the CMS to do it's job, and built solid profiles for all your devices (including learning how to build an appropriate displayl profile that will provide a visual match) it just works.

[Robert Ardill]

In fact colors used in the working space are never seen on a monitor.  Just because a monitor is "adobeRGB" only means it gamut is similar to AdobeRGB, but that doesn't mean you use aRGB as the profile for the display.  So the colors in an image are always converted via a profile to the device space.

You're right of course ... the working spaces are always converted to the output device (or converted from the input device).

A working space is nothing magic, and it really doesn't matter that it's too large. It's just the bucket that holds the data and can be used by the CMS as the base for the conversions. 

Adobe Lightroom is a perfect example of how it all can work seamlessly and without much user involvement ... a good display profile built to match the output profile, everything in the middle handled internally (in a version of ProPhotoRGB 16bit).  Same thing works equally well with Photoshop if you just trust the CMS to do it's job, and built solid profiles for all your devices (including learning how to build an appropriate displayl profile that will provide a visual match) it just works.

Quite right ... there's nothing magical about a working space. HOWEVER ... to say that all you need are good profiles to overcome the mismatch between device gamuts is not at all true.  If you edit in a large working space like ProPhoto you will inevitably at times have colors that cannot be viewed on your monitor and cannot be printed.  What happens to these colors depends on your profiles and rendering intents, and it is very unlikely that what is rendered on your monitor will be the same as that on your printer.  So you will be well away from WYSIWYG, especially if you use a Perceptual mapping for print since most monitor profiles will be Relative Colorimetric.

On the other hand, if you use Adobe RGB and your monitor covers most of Adobe RGB, what you see on your monitor will be as close as you can get to the actual colors (providing of course you have a good monitor and a good monitor profile).  So at least you will be starting off from a (relatively) known point: the remaining issue of the printer gamut can be dealt with (but not necessarily that easily!) by using soft proofing and gamut warning, providing, again, that you have a good printer profile and well-calibrated printer.

Here is a comparison between my own monitor (an Eizo CG277) and Adobe RGB:



As you can see, the monitor gamut is slightly larger than Adobe RGB (the monitor is the wireframe).



And as you can see here, the density response of the monitor and Adobe RGB are almost identical.

So I can be quite confident that what I'm seeing on my monitor are colors that have not been modified by the CMM (or at least minimally modified).  I also know from the profile analysis that the colors will be within a dE of 1.2 or better, so I can be reasonably confident in the colors.  After that it's down to my eyes and the working environment ... all of which are variable and subjective.

So it's a tradeoff.  If you have too large a working space you are likely to be, at least partly, working outside of reproducible colors.  If you are using too small a working space you may lose some of the vibrance in your prints.  The best compromise, IMO, is to use Adobe RGB since the best monitors currently match this space. If you want to squeeze that extra bit from your printer then Beta RGB is a good choice as it's big enough to cover the gamut of most printers and not too much bigger than the (Adobe RGB) monitor gamut.

Robert

[Wayne Fox]

I don't want to get into a big debate here and not going to spend a lot of time on this.  It has been discussed and argued ad nauseum, and there is little point in spending a lot of time rehashing all of this.

 However I do believe you are making some assumptions that are not accurate, and I would submit that if your practice was best practice it would be preached by many experts, when in fact they do not.  Rather than get into a debate I would just like to make a couple of points for the sake of the OP and others who stumble across this thread, and encourage them to do some research.  And to be clear, it's not that your approach won't offer great results, but the assumption that using a prophotoRGB/16bit workflow is looking for trouble is just not true.

Your assumption is that because a display is similar in gamut size to AdobeRGB the CMS will have to make little to no changes and you will see the colors as they are by using AdobeRGB as the working space offers such superior results that it is worth doing despite having to clip out colors that are outside of AdobeRGB that exist in the file as well as lose colors that the printer is able to print but are outside of aRGB (which with some printers are not insignificant). This is supposed to be more "wysiwyg" and thus is worth sacrificing the the colors out of the AdobeRGB space.

 First I don't know whether you can verify by the 2 graphs you display that there isn't a lot more going on in the conversion process. Second, I don't see much difference between the argument that you should use AdobeRGB over sRGB because the printer can print colors outside of sRGB than it would be applying the same logic to using ProPhotoRGB over AdobeRGB, because with some current printers the color advantages over AdobeRGB are pretty large.  (the z3100 isn't one of those, it's pretty old technology and is pretty weak in the reds compared to the z3200 as well as the ipf8400 and epson x900 printers.)

But more importantly,  I'm not sure how mapping and clipping the colors into the AdobeRGB space and then to the display space will offer any advantage over leaving the colors as they were and  just mapping the colors into the display space dynamically, and into any other output space as needed. This goes against the very premise of a good color management system.  In fact I would bet that two appropriately setup and profiled systems side by side, one where a file is forced into the AdobeRGB space before being opened, the other which leaves the file in a ProPhotoRGB/16bit space will be virtually identical, the only difference might be very subtle tonal gradations that are maintained by the system using ProPhotoRGB - most likely so subtle many people wouldn't even be able to see them upon close examination. You state how well your system works for this ... I don't think it's any better than what I'm doing which offers me an almost perfect visual match to my output, and rarely do I have to tweak or change anything after printing out a file.

As far as using a space other than ProPhotoRGB that is smaller, again I'm not sure why this is relevant. It doesn't really matter that the container is larger than the colors in the file .. it's not like the unused colors change anything.  The only issue with ProPhotoRGB is the available number of colors in an 8bit file isn't sufficient, so you have to stay in 16bit mode to avoid banding. I suppose if a perfect space existed that only contained colors needed it might be small enough that working with 8 bit files would be adequate.  But then again, it seems that everything is moving past this anyway, with 10bit workflows on the horizon which will require working with 16bit files.

I as said, this doesn't mean  great results can't be obtained by using AdobeRGB, because the results are more about user skill and quality profiles, but anyone using a ProphotoRGB/16bit workflow and getting into trouble because of it needs to look somewhere other than blaming ProPhoto for their problem. Certainly restricting things to AdobeRGB might seem to fix it, but it's more likely applying a bandage rather than really fixing whatever the underlying problem might be.

[digitaldog]

One reason we need big RGB working spaces is that they are based on theoretical emissive devices (ProPhoto being very theoretical when you look at what falls outside human vision). Necessary because of their simple and predicable shapes. So while there are many more colors that can be defined in something like ProPhoto RGB than you could possibly print, we have to deal with a significant disconnect between these simple shapes of RGB working space and the vastly more complex shapes of an output color space. Simple RGB working space matrix profiles when plotted 3 dimensionally illustrate that they reach their maximum Chroma at high luminance levels which makes sense since they are based on increased Chroma by the addition of more light. The opposite is seen with print (output) color spaces where this is accomplished by adding ink: a subtractive color model. One reason we need such big RGB working space like ProPhoto RGB is due to its simple size and to counter the disconnect between mapping to the output space without potentially clipping colors. There can be issues where very dark colors of intense Chroma (which do occur in nature and we can capture with many devices) don’t map properly with a smaller working space. Many of these darker colors fall outside Adobe RGB (1998). When you encode using a smaller color space, you clip the colors to the degree that smooth gradations become solid blobs in print, again due to the dissimilar shapes and differences in how the two spaces relate to luminance. I suspect this is why Adobe picked ProPhoto RGB primaries for the processing color space in their raw converters.

When I get back from location, I'll be finishing up this video on the subject (URL for rough cut below):
http://digitaldog.net/files/WideGamutPrintVideo.mov
And fix the title typo <g>.
I think part 3 illustrates this idea of color clipping.

[JRSmit]

In addition, a serious study by the US museums , I forgot the acronym, showed that the encoding in color spaces like aRGB op propohtotrgb has insignificant impact on quality of the color itself, how the encoding was done (ie what tools used)  does matter though.

[Robert Ardill]

I have nothing against ProPhoto and do use it at times, if the image warrants it.  However most of our images don't, with the colors falling naturally within smaller spaces like aRGB or even sRGB.  It makes sense to use a very wide working space at the capture stage since our cameras are capable of capturing a wide gamut, and if you can only pick one working space (as is the case for Lightroom), then pick a wide one.

Our problem is not in the wideness of ProPhoto - it's that ProPhoto allows us to do edits that fall outside of both human vision and our current monitor gamuts.  So unless we're careful when editing (for example by always turning on soft-proofing and checking both monitor and output device out-of-gamut while we are editing) we can quite easily end up with colors that look great on screen, but only look great because the mapping to the monitor is OK.  That doesn't mean that the same (unviewable and unprintable) color will also print well ... that depends entirely on the output profile, and if you choose a perceptual mapping the chances are quite high that there will be a significant shift in all the colors on your print (might look fine, but it will be different to what is intended).

The advantage of using aRGB is that to the extent that the monitor is capable of doing so, it will show the colors as they are ... and aRGB will prevent us from going outside of the monitor gamut.  We then only need to concern ourselves with the printer gamut.

If you're printing from Lightroom from the raw file then there is no option: you have to print from ProPhoto and so you need to be quite careful.

If you go into Photoshop first (as I always do) then there is a choice at the time of opening the image of choosing ProPhoto or aRGB.  If the image is within aRGB at that stage then I doubt that there is any damage done to the image in choosing one over the other.  So my recommendation would be aRGB at that point.  If the image is NOT within aRGB, then the choice IMO is either to bring it back into aRGB-line, or open it in ProPhoto.  The decision for me is based on whether the OOG colors are within my printer gamut or not: if they are then I will use ProPhoto, if they are not then I will bring the image back into line.

All of our editing is done using our monitor: that is the controlling device effectively.  If we go outside of its gamut we are asking for trouble.  We may well get away with it, but we may not ... it's a matter of chance.  If we want to be safe (but a little more limited) then we would be wise to stay within the monitor gamut.

I don't personally worry about what will happen when a much wider gamut monitor or printer becomes available - because I always keep my raw files so I can always go back, if I feel that it might improve the image, and make the little tweaks that will get me that extra bit of sparkle that has become possible.

My last monitor had an sRGB gamut (more or less) and I processed my images in sRGB.  When I go back and view them on my now aRGB (more of less) monitor, the vibrance of the image has so far never been an issue for me and I have not reprocessed any image for that reason. What I have done is to reprocess images because I now have better sharpening tools, my own skills have improved (I think and I have better papers. 

But anyway ... there are swings and roundabouts and as we said on another thread, what we are trying to do is to fit a round peg into a square hole ...

Robert

[Wayne Fox]

I think sometimes there is a disconnect with the concept of “color” when we are talking about working spaces and output spaces.  Perhaps to some the use of the word color inherently implies some bright vivid color.  But in my workflow these aren’t the colors I’m worried about.

The idea that because ProPhotoRGB deals with colors outside of human perception means you can end up editing colors you can’t “see”, while theoretically true, doesn’t seem to be true from a practical use point of view.  By the time you get to those colors, even if your display is a sRGB display the colors will be garish and obviously not right (unless that’s what you want). So while logically it’s easy to believe this to be a problem, it really isn’t.

But as Andrew mentioned, the more important colors which can be affected, the colors that your printer can print that are sacrificed if you force your image into an AdobeRGB working space are in the midrange and darker tones - especially shadows.  And if you clip those into AdobeRGB, you are sacrificing potential shadow detail and may even block up some of those shadows. And we’re not talking about a small amount of colors. AdobeRGB wasn’t developed with reflective output in mind ... it was developed for emissive devices.  So as a working space in  a workflow whose primary purpose printed output on high end inkjet printers, it’s really isn’t a great choice.

A workflow that leaves colors alone, then can dynamically map them into an output space as needed, using a different rendering intent to preserve relationships between colors when necessary, to me is a much preferred workflow.  While I have many clients and students in my color management classes that state these same worries, I’ve never really seen anyone that finds it a problem if they have their system setup correctly and use good technique.

Attached are 2 colorthink graphs showing the colors that are achievable from an Epson 9900 printer on Epson Premium Luster and a Canon ipf8400 using Canon Premium Glossy paper that are outside of AdobeRGB ... .

[digitaldog]

Our problem is not in the wideness of ProPhoto - it's that ProPhoto allows us to do edits that fall outside of both human vision and our current monitor gamuts. 

Not a major issue if you edit carefully. As I outline in my video, you have to decide what's more important: contain colors you can't see on the display but exist in the capture and can be printed OR funnel into a smaller color space so you can see it all and not use it all. If print is your final output, using a smaller gamut working space can reduce the qualities of said output as I explained below.

Going back to the raw if fine IF you haven't spent hours editing the master image after raw rendering but prior to printing.

[JRSmit]

turning on soft-proofing and checking both monitor and output device out-of-gamut while we are e.

If you're printing from Lightroom from the raw file then there is no option: you have to print from ProPhoto and so you need to be quite careful.

Do not understand this statement. I use LR both for developing and for printing. Softproof allows me to see where colors in an image are out of gamut for given destin profile, so i can do that also for sRGB or aRGB .
Unless you are radically upping the saturation, i cannot see a problem.

[Robert Ardill]

Do not understand this statement. I use LR both for developing and for printing. Softproof allows me to see where colors in an image are out of gamut for given destin profile, so i can do that also for sRGB or aRGB .
Unless you are radically upping the saturation, i cannot see a problem.

Yes, actually if you stick to Lightroom and you do use the soft-proof feature with gamut warning then you are being very careful and won't get into problems: the softproof shows both out-of-gamut monitor colors and also out-of-gamut destination colors. 

If you're working from Photoshop it's more difficult as you can't see both at the same time (but of course it's pretty easy to set up a script to toggle from monitor to destination, so it's not that difficult).

There's nothing wrong with using ProPhoto or other wide working space ... as long as we know what we're doing, and we are consistently careful.  If we want a workflow that is quick and easy and doesn't require careful checking ... then there is an advantage in using a smaller working space because it reduces the risk of inadvertently going badly out of gamut.

There is also nothing wrong, IMO, in using several working spaces. If we know that an image is well within sRGB - then why not use sRGB? For example, if our images are monochrome or nearly so then we won't be using a fraction of sRGB.  On the other hand, if we have a particular image that has a very saturated sunset that we want to print - well then we may need to go to ProPhoto.

It's like ... use your bicycle to go down to the village and your 4x4 to go up the mountains.  Neither is better than the other but each has its particular strengths.

I would think that the best solution is to buy GamutVision or Chromix and then the decision as to which color space to use becomes quite easy.

Robert

[Robert Ardill]

One reason we need big RGB working spaces is that they are based on theoretical emissive devices (ProPhoto being very theoretical when you look at what falls outside human vision). Necessary because of their simple and predicable shapes. So while there are many more colors that can be defined in something like ProPhoto RGB than you could possibly print, we have to deal with a significant disconnect between these simple shapes of RGB working space and the vastly more complex shapes of an output color space. Simple RGB working space matrix profiles when plotted 3 dimensionally illustrate that they reach their maximum Chroma at high luminance levels which makes sense since they are based on increased Chroma by the addition of more light. The opposite is seen with print (output) color spaces where this is accomplished by adding ink: a subtractive color model. One reason we need such big RGB working space like ProPhoto RGB is due to its simple size and to counter the disconnect between mapping to the output space without potentially clipping colors. There can be issues where very dark colors of intense Chroma (which do occur in nature and we can capture with many devices) don’t map properly with a smaller working space. Many of these darker colors fall outside Adobe RGB (1998). When you encode using a smaller color space, you clip the colors to the degree that smooth gradations become solid blobs in print, again due to the dissimilar shapes and differences in how the two spaces relate to luminance. I suspect this is why Adobe picked ProPhoto RGB primaries for the processing color space in their raw converters.

When I get back from location, I'll be finishing up this video on the subject (URL for rough cut below):
http://digitaldog.net/files/WideGamutPrintVideo.mov
And fix the title typo <g>.
I think part 3 illustrates this idea of color clipping.

Hi Andrew,

I had a look at your video ... very well done as usual!  In general I think your recommendations are fair, however comparing ProPhoto to sRGB is not really.  It gives the impression that the wider the better, which is not necessarily true.

Here is a gamut map of Adobe RGB and the Epson 9900 with Canson Photo Hi Gloss paper (about as good a combination as one can get at this stage, gamut-wise):



It is clear that even with Adobe RGB there is some possibility of clipping/shifting in the darker regions (as well as the lighter ones).  However the clipping is minimal in the darker regions and certainly will not clip to black.  There is of course considerably more clipping using sRGB and it makes no sense to have a printer like the 9900 and then printing saturated images from sRGB.  With aRGB it's a judgement call, as you say in your video: have colors that you can't see but can print, or see what you are going to print and take the hit on some of the saturated colors.

What you don't really say in your video is what things look like with ProPhoto. Here it is:



No clipping admittedly .  But look at all of the colors that are entirely unprintable and unviewable!  So ProPhoto needs to come with a very big warning.  If you print using a perceptual mapping you will, in all probability, get a serious color shift when printing from ProPhoto. Depending on the profile this could even happen if NONE of your colors are outside of the printer gamut (because some profiles compress the whole of ProPhoto into the destination gamut ... and they do this because they have no way of knowing at the time the profile is made what colors will be outside the destination gamut).

So it's one of these things: if you want to squeeze the utmost from your images then sure, go for a wider gamut than Adobe RGB (Beta RGB would be a better choice than ProPhoto) ... but if you don't fully understand what is happening and don't know how your printer profiles have been built you could end up with unintended colors on your print; if you are willing to sacrifice a bit of the most saturated colors and be safe then you would be better off staying in Adobe RGB; if you want a compromise between these two then an intermediate working space like Beta RGB would be a good choice.

IMO, at any rate

Robert

[digitaldog]

It gives the impression that the wider the better, which is not necessarily true.

No, it absolutely IS true with those images from raw, printed to an Epson! That's the point of the video in part. To allow you or anyone to run the tests themselves with my images or yours. With my images, to my printer, it is without question that the ProPhoto encoding is vastly superior when viewing the print compared to sRGB.

It is clear that even with Adobe RGB there is some possibility of clipping/shifting in the darker regions (as well as the lighter ones).

Clear on the gamut map or the print? Kind of a big difference no?

[Wayne Fox]

So ProPhoto needs to come with a very big warning.  If you print using a perceptual mapping you will, in all probability, get a serious color shift when printing from ProPhoto.

I guess I'm not quite sure how you arrive at this. Using a perceptual intent happens when you map the colors from where they are into an output space. The container and it's size doesn't really affect the actual colors that are in the image.  Even if the image starts out with colors contained in lowly sRGB and you work in the ProPhotoRGB space, the colors are still the colors.  Just because the space is bigger, nothing is mapped into all those unused colors - you don't use a perceptual intent to map those colors into ppRGB. And when you map them into an output space, it is that space that determines where they end up. If the output space isn't large enough to contain them, at that point they need to be adjusted into the space.  So the working space has no affect on that.  You aren't going to get some weird result because you have an image whose colors are all contained in sRGB, and you are working in ProPhotoRGB and then want to output to some device. Now you might get into trouble if you are working with an sRGB image and then change your working space into ppRGB ... but even this is pretty unlikely, and once you start in sRGB or aRGB there isn't much point in moving to ppRGB.

But there is a risk of losing quality/shadow detail if you original data is contained within sRGB so that's where you start, but needing to modify it to the point (especially when pulling shadows open) that will require colors outside of sRGB.  True it won't be dramatic, but I guess that's the concern I have with your earlier statement of using sRGB or aRGB when you can. I can't see an efficient workflow where I can predetermine whether or not I will only need colors inside of sRGB or aRGB so I can choose those for a working space instead of ppRGB.  You can't easily tell this visually, and in fact many more image than you realize can take advantage of printer colors outside of aRGB.

I have a hard time seeing anyone with an image whose data is contained within sRGB stretching it to the point it ends up in the colors of ppRGB anyway ... this is a big stretch so most likely whoever would do this would kill the image even if they were in sRGB  If they are really that unskilled using aRGB or sRGB may be sort of a safety net, but I still think if they are at that level it won’t turn out great most of the time no matter what space they use. (and i see sRGB images come into my shop every day to be printed that really are poorly done).

I really think your logical thought process (and the idea the ppRGB is "so big") has you creating problems that really aren't there.  And while ppRGB has colors outside of human perception, out of the 3 color spaces it is the only one created specifically with photography in mind.  The goal when created by Kodak was a space that could contain all the colors that naturally occur in the world ... not a space that is to be used when working with emissive computer displays and CMYK printing processes.  Yes this means you end up with some "colors" that aren't colors, but it's really not as problematic as you believe.

[digitaldog]

I really think your logical thought process (and the idea the ppRGB is "so big") has you creating problems that really aren't there.  

Based on what have to be million's if not more images, run through that space (and through Adobe raw converters), I think you're absolutely correct!

[JRSmit]

Robert, i am lost as to what you try to prove. Would like to see some serious proof of all these theories of colorshifts. I have not such experiences.