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M.Chapman

Useful sRGB AdobeRGB test images?

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26 minutes ago, M.Chapman said:

 

I'm sorry I think you are still misunderstanding what assigning and converting (in the software) actually do. The colour numbers are the values in the file, before the profile is applied. Applying a profile leaves the colour numbers unchanged, but may change what appears on screen. Converting changes the colour numbers, but when the new profile is applied the colours on screen shouldn't change.

 

Mark

 

I do understand exactly Mark. But I now give up this conversation. It has taken too much precious time and is getting nowhere. No bad feelings in that - just time to move on.

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1 hour ago, MDM said:

time to move on.

Yes, there so many dancing angels that some of them are falling off the head of the pin.

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12 minutes ago, spacecadet said:

Yes, there so many dancing angels that some of them are falling off the head of the pin.

 

I'm not religious so angels are out of gamut for me 😇. I do, however, believe in colour management which means I also believe in the first law of colour management - you don't need to understand the physics to use it. The third law is that it is futile to worry about what those who don't believe in colour management see when they look at an image that one has carefully colour managed. 

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Posted (edited)

I've found this thread very useful in that it has made me aware that Apple Retina displays are high-quality wide-gamut displays, albeit in the P3 rather than AdobeRGB colour space. I knew they were high resolution of course but hadn't known that the way they they deal with colour is so much better. These screens on Macbooks & Imacs are very mainstream which has only happened in the last few years so I think it is worth considering in this changing world whether supplying untagged sRGB images by Alamy should at least be up for review. It's clear that certain images in a wider colour space such as P3 or AdobeRGB will now look better than straight sRGB  images on these screens and that buyers might therefore expect them to do so.

 

It's also worth thinking about whether even these untagged sRGB images from Alamy will be correctly displayed on these devices and that would seem to be down to how the web developers deal with it. This article from Webkit from early 2016 explains how they responded to the new wide-gamut Apple devices, and what measures they put in place to make sure that even untagged sRGB images would be at least be displayed as intended.

 

https://webkit.org/blog/6682/improving-color-on-the-web/

 

It also links to a page of examples to show the differences:

 

https://webkit.org/blog-files/color-gamut/

Edited by Harry Harrison
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Posted (edited)

Another useful post Harry. I'd found the example images previously (he uses  a similar technique to the one I used to create my test images) but hadn't read the article. I note the article is from 2016 so I wonder what's changed since? Certainly colour managed browsers that can render sRGB and AdobeRGB (and I assume P3 too) seem to be pretty standard now.

 

The author addresses one aspect which is how to display a wide gamut image on an sRGB display. This is done by conversion of the image data to sRGB (with no control over the method - perceptual, absolute etc.) or by detecting the display in use and serving up the a pre-converted (to sRGB) version of the image. The vast majority of folks, even on a wide gamut display wouldn't notice the difference between those two options, providing as perceptual or relative colorimetric conversion is used.

 

It also mentions the treatment of untagged images - i.e. treat as sRGB

 

What it doesn't cover is the issue you raised earlier. Alamy have a massive library untagged sRGB images. What happens if the market starts to demand wide gamut images or display them on wide gamut displays?

 

We know that if an untagged Alamy image is currently displayed on a wide gamut monitor it will be rendered in sRGB [apart from Firefox 77.0.1see this thread]. So what does this mean in terms of colour accuracy?

  • If the image was submitted by the contributor to Alamy as sRGB, then the user will see a good reproduction of what was uploaded. The image will not contain the more intense colours that AdobeRGB or P3 gamuts, or their monitor is is capable of displaying. But then, nor did the original sRGB image that was uploaded, so that's OK.
  • If the image was uploaded to Alamy as AdobeRGB, then the original may well have included some of the more intense colours that AdobeRGB can render. But, when Alamy convert the image to sRGB, this extra information will have been lost and those colours will have been "clipped". (The exact way in which the colours in the image are "adjusted" will depend on whether Alamy uses perceptual, relative colorimetric etc. conversion. This could be important... See later...). When the sRGB image, without profile, is shipped to the customer how it will be rendered is up to them and how they "treat" the image. But the "wide gamut" colour information has already been discarded at Alamy, before they receive the image.
    • If they load the image into a web-page "as is" (untagged) then it will be displayed as sRGB. If they convert to the image to AdobeRGB the colours in the image will not change (nor will the appearance of the image apart from potentially some banding). In both these cases the image will appear less intense than the one uploaded by the contributor if the original image contained colours that were outside sRGB colour space.
    • If they assign an AdobeRGB or P3 tag to the image, the colours in the image will be boosted. This will give a "richer" rendering of landscape images that some folks might prefer, but could give problems with other types of image (intense clipped colour areas, poor skin tones etc.) 

I wonder if there's any software that can attempt to "renconstruct" those lost colours? A bit like some of the sophisticated shadow and highlight recovery tools? If the original AdobeRGB to sRGB conversion method was known (presumably Alamy have only used one of them) is there some way of intelligently boosting the colours to give the "impression" of a wide-gamut image? For example - suppose this process was carried out at Alamy. Open the sRGB image, convert to AdobeRGB (to provide free space for extra colours). Apply small (intelligent?) boost to colours but excluding skin tones, and resave with AdobeRGB profile?

 

Alamy would also allow new submissions to be made in AdobeRGB or P3 colour space and would not convert to sRGB (unless the customer selected an sRGB image) and they would ship with the profile attached.

 

They would also provide an easy way for contributors to upload replacement genuine wide gamut version of their existing images without needing to re-keyword and caption etc.. QC would still occur n these replacement images on a sampled basis.

 

Mark (just musing)

Edited by M.Chapman
Added link to thread on bug in Firefox 77.0.1

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Posted (edited)
5 hours ago, spacecadet said:

Yes, there so many dancing angels that some of them are falling off the head of the pin.

 

I'm really not sure how to take that. If you're not enjoying the thread I started, why read it?

 

Mark

Edited by M.Chapman

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37 minutes ago, M.Chapman said:

(just musing)

....and it's worth musing about I think, simply because what has changed is that a lot of people around the globe are now looking at images on Macs with the potential to display the wide gamut P3 colour space, many are presumably also looking at them on Surface Pros and the latest televisions ('television' hardly seems like the right word for them now).  As far as what has changed since that article in 2016 I doubt anything has, it was I think simply describing how they had addressed the onset of Retina displays, and clearly they did have to address it.

 

Regarding my meanderings about 'converting; an AdobeRGB that has been converted to sRGB back up to AdobeRGB, I suppose it's just going to look like the sRGB image which is probably what you said, but it's not going to look like the original AdobeRGB image, but then you didn't say that. Yes, it doesn't seem to be outside the realms of possibility that they could digitally enhance the image to give at that extra pizazz, your intelligent boost, but then we would be throwing out Colour Management with the bath water.

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1 hour ago, Harry Harrison said:

but then we would be throwing out Colour Management with the bath water.

But then conversion of AdobeRGB to sRGB is hardly good colour management either.... not to mention shipping without a profile...

 

I also found this on Adobe's website which gives details on Profile Assignment and Profile Conversion.

https://helpx.adobe.com/uk/photoshop/using/working-with-color-profiles.html

 

Mark

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Posted (edited)
16 hours ago, Harry Harrison said:

Yes, it doesn't seem to be outside the realms of possibility that they could digitally enhance the image to give it that extra pizazz

 

I'll do some Googling to see if anything comes up. This has to be a widespread challenge/opportunity?

 

Mark

Edited by M.Chapman

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Posted (edited)
On 13/06/2020 at 17:48, M.Chapman said:

 

I'm really not sure how to take that. If you're not enjoying the thread I started, why read it?

 

Mark

No offence meant. It was intended to be humorous and certainly wasn't aimed at anyone in particular because I wasn't aware who started it.

Actually I'm not reading it in any detail, just marvelling at the length of the posts and wondering what relevance it might have. To a colorimetrist I'm sure it's fascinating, but to a photographer, at least this photographer, not so much.

Still, it's something to do. We need something. I'm photographing jewellery, for goodness' sake.

Edited by spacecadet

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Posted (edited)
1 hour ago, spacecadet said:

just marvelling at the length of the posts and wondering what relevance it might have

Believe me, it doesn't come naturally to me but its relevance I think is that with many people, not just photographers, moving to Retina displays it's possible that the system Alamy has admitted to using where they convert all images to sRGB and strip the final output files of their profiles may mean that they don't look as good as they should do on these displays. The problem is not the conversion to sRGB (where necessary), though AdobeRGB would potentially better for certain higher end applications, but the fact that they provide them without a profile. Work in progress I think. Anyway, back to photographing the garden.

Edited by Harry Harrison
expanded on AdobeRGB a little
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I've consolidated my suite of test images and made them all available here.

Apologies for the rudimentary html, but I needed to be sure the images being "served up" are not being altered by host site (converted to sRGB etc) so didn't want to use an image hosting site. The images can be downloaded by Right-click>Save As... if you need to inspect more closely.

 

Mark 

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