ipf8400 gamut

[Robert Ardill]

OK, no problem ... I'm thoroughly tired of this discussion too, and like you I feel that I'm wasting my time and that all we're doing is going round and round.  It reminds me of the tower houses in the Peloponnese in Greece which were built so that neighbors could lob stones at each other from the relative safety of their own massive walls.  At harvest time they called a truce so they could get their crops in and after the harvest they would start again.

But I have to say, Andrew, that I am disappointed that you didn't answer the two simple questions I've been asking you regarding your video: since this is out there for the public to view, it would be good to get a statement from you regarding exactly what is happening when you convert the image to sRGB, why the clipping/flattening occurs, and whether or not this is a fundamental problem with sRGB, or whether it is a fundamental problem with converting an image with a wide gamut which is in a wide-gamut working space to a working space with a small gamut.

Robert

[Robert Ardill]

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

I've had a look back over this thread, as I said I would, as I was concerned that I had been possibly rude or aggressive, or that I might have unintentionally said things that are incorrect. 

There's no doubt that things did take a turn for the worse, but it is easy to trace it back to this post of mine (quote above).  I think it is also easy to see that the issues have to do with my criticism of Andrew's video, and what seems to have been taken as a criticism (or dislike) of ProPhoto.  I certainly have no strong views about ProPhoto since it's just another working space ... except to reiterate that it does need to be used with some caution because it is much wider than all of our current output devices or monitors.

So it would seem that the point at which the discussion became a bit edgy was over Andrew's video.  My view of that hasn't changed, as I do not think that it is valid to criticize sRGB (or any smaller working space) by clipping colors from ProPhoto (or any larger working space) into the smaller working space.  Chopping colors from a large to a smaller working space is not a demonstration that the smaller working space is inferior or that the large working space is superior: it is simply showing that the smaller working space cannot contain the full range of colors that the larger working space can.

I would still like Andrew to address this point, although I don't suppose he will.

Robert

[John Hollenberg]

Chopping colors from a large to a smaller working space is not a demonstration that the smaller working space is inferior or that the large working space is superior: it is simply showing that the smaller working space cannot contain the full range of colors that the larger working space can.

If you like your colors dumbed down, I guess that is fine.  I can't imagine many people would aspire to that if they plan to print their work on an inkjet printer.

[Schewe]

I would still like Andrew to address this point, although I don't suppose he will.

I thought this beaten horse was dead…didn't we say it was dead? It sure smells dead. Please, let it be dead...

[Robert Ardill]

If you like your colors dumbed down, I guess that is fine.  I can't imagine many people would aspire to that if they plan to print their work on an inkjet printer.

No, I don't like my colors dumbed down John.  The point is that if you already have colors that are within a particular working space (say Adobe RGB for sake of argument), then printing them from Adobe RGB or converting them to ProPhoto RGB before printing will give the same results: the ProPhoto colors won't be more saturated (or less dumbed down).

If you convert the colors from Adobe RGB to sRGB you may or may not be dumbing down the colors: you will be if the image colors are not within the sRGB gamut, otherwise you won't.

So the critical thing is not the working space gamut, or the destination gamut, but the image gamut.  As long as the colors that are in the particular image are fully contained in both the working space gamut and the destination gamut, all will be fine.  It's when the working space and/or the destination space are smaller than the image gamut that the image colors will have to be shifted or clipped (either by the photographer, or by the CMM).

We can either work in a larger working space for all of our images, one that can contain all of the colors of all of our images, or we can pick the working space to be big enough to contain a particular image's gamut, and do this for each image.  There are pros and cons to both of these options, but it is not true to say that one is inherently better than the other, providing that each is used with understanding and care.

What is certainly true is that if your image colors can not be contained in a smaller working space, and you convert them colorimetrically to a smaller working space , you WILL cause the out of gamut colors to be clipped.  If you convert them using a perceptual mapping (which you can't do, directly, from working space to working space) then the colors will be shifted. That does not make the smaller working space inherently bad ... it just means that it is too small for this particular image.

Robert