Conditions When Editing

[Manfred M]

Thank you Ted! I've read it a few times now and am following it to the best of my ability.

It refers to the over-saturation of colours in "untagged objects" I don't know what they are: would they include my photos when looked at in Lightroom? What about the photos that I see posted in CiC? I will keep looking for a definition of that term that I can understand.

The author also says:
If color management is set up properly on your system, it will compensate for whatever color space your display uses and you should see consistent color.

So I will try calibrating with i1 Pro again but this time following the company's longer set of instructions for when your Mac gets poor results after the first attempt.

Catherine - a few clarifications...

An untagged object is one that has no assigned colour space identified, so the software won't know how to properly interpret the colour data. In general, most colour managed software defaults to the sRGB colour space. I used the ProPhoto colour space on both images here. This is what happens....

1. Converted to sRGB





2. ProPhoto RGB interpreted as sRGB. The colours look desaturated and not at all what they should look like.




In general, anything posted to the internet should be converted to sRGB, as all browsers can handle that colour space. Not all browsers properly display wide-gamut colour spaces.

The author is correct. The computer's operating system should display colours properly, based on the operating system that is being used; but that assumes the colour profile that is being used is appropriate.

[xpatUSA]

Utilities called EXIF Viewers can usually show you whether your images have embedded profiles or not. If not, your stuff will assume sRGB - even if you shot and edited in Adobe RGB ...

Here's an image which I edited and saved in ProPhoto color space - it has a ProPhoto color profile embedded in it:



Here's the same image with the color profile removed:



See a difference on your screen? On mine the second image is dull ...

[edit] I see that Manfred also illustrated what I said in #20 in exactly the same way; great minds think alike, eh?

[CatherineA]

Thank you very much Ted and Manfred for explaining - and illustrating - untagged objects!

With respect to those out-lying greens, it would have been interesting to actually see an image of a monitor showing the greens that the iMac misses. Or maybe there are prints showing those colours.

[Manfred M]

Thank you very much Ted and Manfred for explaining - and illustrating - untagged objects!

With respect to those out-lying greens, it would have been interesting to actually see an image of a monitor showing the greens that the iMac misses. Or maybe there are prints showing those colours.

Okay - Let me try. There are all kinds of assumptions in what I am going to show, but by using Photoshop's soft proofing functionality, I can demonstrate at a high level what the different colour spaces will do. The big "gotcha" is that these are all screen shots taken of my AdobeRGB compliant screen. I've picked a sample image that is high in values that will be out of gamut in the P3 colour space. The actual colour spaces used in the soft proofing are shown in the display box on every screen shot.

THE GRAY AREAS ARE THE OUT OF GAMUT AREAS IDENTIFIED BY THE SOFT PROOFING.

1. ProPhoto RGB - Everything in in gamut.






2. Print soft proof using my Epson P800 printer using Epson Premium Photo Glossy Paper. Very little is out of gamut. With the appropriate printer ink set and paper, a modern photo printer will exceed the AdobeRGB colour space.






3. Adobe RGB - Some portions of the image are out of gamut.






4. P3 Colour Space - more areas in the blue / green range are out of gamut when compared to the Adobe RGB colour space.






5. sRGB (as expected) handles the narrowest colour range of all the colour spaces tested.

[Manfred M]

Manfred, my post was quite specifically about the perceived but distorted amount of difference between the gamuts when shown in xyY space, especially in the greens. This amount of difference is more properly shown in the perceptually uniform spaces such as CIELUV or CIELAB. From Chavez' diagram I posted, it is obvious what the differences are, being undistorted by xyY's stretched greens.

Roll on Rec. 2020 - a truly wide-gamut ... not unlike Adobe's Wide Gamut or even CIE's RGB ...

Ted - that happens whenever one tries to plot a 3-D representation on a 2-D surface. Look at how distorted the globe looks when presented in a Mercator projection.

Unless we get a device that can actually display the full Rec. 2020 or Rec. 2100 colour space, I'm not sure how excited I can get about them... Even the "best" screens on the market today can at best display 100% Adobe RGB with around a 10-stop dynamic range (i.e. 1000:1 contrast ratio).

[CatherineA]

Thanks for posting the comparison images, Manfred. Do you work from a monitor that displays - more or less - what is shown in image 3, the Adobe RBG? (without the grey of course)? I don't know how all the colours in ProPhoto can be displayed but I think that means I have to read more to understand this better.

You and Ted have helped set me down the right path and thanks very much for that.

[Manfred M]

Thanks for posting the comparison images, Manfred. Do you work from a monitor that displays - more or less - what is shown in image 3, the Adobe RBG? (without the grey of course)? I don't know how all the colours in ProPhoto can be displayed but I think that means I have to read more to understand this better.

You and Ted have helped set me down the right path and thanks very much for that.

The top shot is a screen shot of what my computer screen can display; it is almost 100% Adobe RGB compliant (image 3). I run a dual screen setup. I have a sRGB compliant screen as well, but I use that as a secondary display where I park peripheral items, like the menus I use in Photoshop, so that I do have a very wide open workspace with little clutter.

There are two components when it comes to displaying colours. The first is that the colours have to be in the image, so an image that has no colours that are out of gamut for the colour space; those will display correctly without the operating system having to apply a rendering intent.

This image seems to have no areas that are out of gamut, even when using the sRGB colour space.



It has subtle, muted tones, so this is not surprising. The shot of Niagara Falls has brilliant, saturated colours, so one would expect issues, even with wide gamut colour spaces.

The majority of computer screens that are in use throughout the world have, at best, sRGB compliance and frankly most low end screens don't even meet that low standard. Wide gamut screens have been out for quite some time; I've been using one for about 10 years. They are of little interest to people who are not working in graphic arts who are trying to get as much subtlety and colour range into their work as possible. This is especially true of fine art photographers who are creating quality prints.

There are no ProPhoto RGB compatible computer screens on the market; even the very best ones just barely get the full Adobe RGB colour space covered. In terms of how well the P3 colour space is covered by the current iMac screens is not clear, but the article I linked to in #2 suggests the compliance is less than 100%.

[xpatUSA]

Ted - that happens whenever one tries to plot a 3-D representation on a 2-D surface. Look at how distorted the globe looks when presented in a Mercator projection.

Manfred - the CIE 1931 xyY chromaticity diagram has absolutely no relationship with the Mercator projection, as far as I know. By "distortion", I am referring to the work of MacAdam; I had assumed that you were surely aware of it:

https://en.wikipedia.org/wiki/MacAdam_ellipse

But the mention of Mercator makes me less sure, I must admit ...

Unless we get a device that can actually display the full Rec. 2020 or Rec. 2100 colour space, I'm not sure how excited I can get about them... Even the "best" screens on the market today can at best display 100% Adobe RGB with around a 10-stop dynamic range (i.e. 1000:1 contrast ratio).

I'll take your word for it; I'm still on 100% sRGB, quite enough for these old eyes ...

[xpatUSA]

I don't know how all the colours in ProPhoto can be displayed but I think that means I have to read more to understand this better.

Just so's you know, Catherine, 'ProPhoto' should almost not be called a color space because many of it's values can not seen by humans and therefore are not actually colors. So, even if those values could be displayed somehow, you wouldn't be able to see 'em.

[george013]

Catherine,
Read next articles. On page 2 there is a test showing you if your browser is "respecting an embedded colour profile". I think you look through a browser from post 12.
I forgot the link http://regex.info/blog/photo-tech/color-spaces-page2
George

[Manfred M]

Manfred - the CIE 1931 xyY chromaticity diagram has absolutely no relationship with the Mercator projection, as far as I know. By "distortion", I am referring to the work of MacAdam; I had assumed that you were surely aware of it:

https://en.wikipedia.org/wiki/MacAdam_ellipse

But the mention of Mercator makes me less sure, I must admit ...



I'll take your word for it; I'm still on 100% sRGB, quite enough for these old eyes ...

I was unaware of the work, but that being said, when we look at light output in the range of 30 cd / square metre I find alarm bells going off. Some of the other studies listed in the article are down at 3 cd / sq m. These studies all use very dim light sources. When the average computer display that is straight out of the box is running at something that is closer to 200 cd / sq m, I wonder how relevant this information really is to someone working on a computer screen. The rods in our eyes are sensitive to lower light levels but do not appreciably contribute to our colour vision so I am not sure if they are relevant the situations photographers are likely to be using in their editing work. I suspect that the principles still apply; humans cannot make out the millions to billions of colours that our computer screens are capable of producing, but the specifics of what we can see is likely unanswered by this work.

[Manfred M]

Just so's you know, Catherine, 'ProPhoto' should almost not be called a color space because many of it's values can not seen by humans and therefore are not actually colors. So, even if those values could be displayed somehow, you wouldn't be able to see 'em.

I've never liked the name "colour space" either, but it is in common use. In my view, these are all really mathematical models that are used to calculate specific values that we can see on our screens. That is likely too much information for the average photographer...

The fact that ProPhoto can create values that we cannot see is really not something that should bother anyone. Our eyes can only capture a small portion of the electromagnetic spectrum, but the parts we can't see can still impact our images, hence the IR and UV filters on the sensor stack in our cameras.

[xpatUSA]

I was unaware of the work, but that being said, when we look at light output in the range of 30 cd / square metre I find alarm bells going off. Some of the other studies listed in the article are down at 3 cd / sq m. These studies all use very dim light sources. When the average computer display that is straight out of the box is running at something that is closer to 200 cd / sq m, I wonder how relevant this information really is to someone working on a computer screen. The rods in our eyes are sensitive to lower light levels but do not appreciably contribute to our colour vision so I am not sure if they are relevant the situations photographers are likely to be using in their editing work. I suspect that the principles still apply; humans cannot make out the millions to billions of colours that our computer screens are capable of producing, but the specifics of what we can see is likely unanswered by this work.

You do our eyes and Catherine a disservice by muddying up photopic (color, cones) and scotopic (grayscale, rods) vision and implying that 30 cd/m2 is insufficient to distinguish color differences or to properly work on a computer screen.

As to display luminance, are you now recommending 200 cd/m2 as opposed to you previous mentions of 80 or so for serious work?

Why did alarm bells go off at 30 cd/m2 ?!!

Wikipedia even considers 10 cd/m2 "well lit":

https://en.wikipedia.org/wiki/Photopic_vision

As to 3 cd/m2 that is at the very upper end of mesopic vision and, therefore, at the lower end of photopic.

Elsewhere, it says "Photopic: This term refers to cone vision and generally covers adaptation levels of 3 candelas per square meter (cd/m²) and higher."

https://docs.agi32.com/AGi32/Content...-_Concepts.htm

In spite of the 'spin' applied in your rebuttal, I maintain that the MacAdam results are valid and have a direct bearing on the perceptual non-linearity of the CIE 1931 chromaticity diagram.

My apologies to Catherine for getting too technical in her thread ...

[Manfred M]

You do our eyes and Catherine a disservice by muddying up photopic (color, cones) and scotopic (grayscale, rods) vision and implying that 30 cd/m2 is insufficient to distinguish color differences or to properly work on a computer screen.

As to display luminance, are you now recommending 200 cd/m2 as opposed to you previous mentions of 80 or so for serious work?

Why did alarm bells go off at 30 cd/m2 ?!!

Wikipedia even considers 10 cd/m2 "well lit":

https://en.wikipedia.org/wiki/Photopic_vision

As to 3 cd/m2 that is at the very upper end of mesopic vision and, therefore, at the lower end of photopic.

Elsewhere, it says "Photopic: This term refers to cone vision and generally covers adaptation levels of 3 candelas per square meter (cd/m²) and higher."

https://docs.agi32.com/AGi32/Content...-_Concepts.htm

In spite of the 'spin' applied in the rebuttal, I maintain that the MacAdam results are valid and have a direct bearing on the perceptual non-linearity of the CIE 1931 chromaticity diagram.

My apologies to Catherine for getting too technical in her thread ...

Ted - you might want to discuss this with curators and photographers who prepare their works for exhibition. They have to deal with not only the physics side of vision, that you seem to concentrate on, but also the physiological and psychological aspects of colour vision that you seem to discount. These are do affect colour vision even more than the pure physics side.

You might want to consider the Purkinje effect in this discussion as both photopic and scotopic components affect our colour vision, at ambient light levels considerably higher than you seem to think. Unfortunately, this side of colour vision does not lend itself to hard data as well as the pure physics side does.

The Kruithof curve is another aspect of colour vision you might want to read up about.

[xpatUSA]

Ted - you might want to discuss this with curators and photographers who prepare their works for exhibition. They have to deal with not only the physics side of vision, that you seem to concentrate on, but also the physiological and psychological aspects of colour vision that you seem to discount. These are do affect colour vision even more than the pure physics side.

You might want to consider the Purkinje effect in this discussion as both photopic and scotopic components affect our colour vision, at ambient light levels considerably higher than you seem to think. Unfortunately, this side of colour vision does not lend itself to hard data as well as the pure physics side does.

The Kruithof curve is another aspect of colour vision you might want to read up about.

Originally, I said "What bothers me generally is the posting of gamuts for comparison in the CIE 1931 chromaticity diagram which is perceptually non-linear (the green is "stretched"). The result is that the Adobe RGB (1998) gamut looks much bigger than sRGB and your iMac's P3 gamut looks much smaller than the Adobe RGB (1998)."

Since then, our discussion has been widened enough to where I am quite reluctant to respond to increasingly wide references to abstruse things like the pleasantness of lighting or the appearance of flowers at dusk which have nothing to do my original comment.

So I'll just end my part in this discussion, if only to give Catherine a break.

[CatherineA]

Hi Ted, I understand why the thread became so technical. No, I don't understand all that you and Manfred have explained, not by a long shot, but I do understand more now and appreciate the time that you have given to this.

Also, I know that CiC is for a wide audience and that includes some people who have a depth of knowledge like yours and Manfred. Sometimes the conversation naturally flows to a deeper technical direction and that is fine by me. I just bow out at certain point and go back to trying to figure out a couple of the monitor display mysteries that are still eluding me. I think re-reading what you and Manfred and George have supplied me with, plus a pot of coffee, should have me sorted out.