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Author Topic: Prophoto, Adobe RGB and SRGB  (Read 1628 times)

Jonathan Cross

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Prophoto, Adobe RGB and SRGB
« on: February 22, 2022, 05:04:18 am »

I have too much time for thinking!  I have Fuji X-series cameras (X-T3 and X-T4), an Apple Mac M1 24" desktop, and a Canon Pro 300 pigment printer.  I use Lightroom Classic and occasionally Photoshop (the latest versions) and for my printer I sometimes use Canon's Professional print and layout.  I use the generic profile for my printer from the paper manufacturer for each of the papers I have.  I always shoot RAW.  I confess that I have not profiled my Apple screen, having had it 7 months.

I understand that Camera RAW uses Prophoto and understand why, but have several questions.

How do the colour gamuts of my cameras compare with the 3 colour systems above?

I have historic RAW images in my LR catalogue that were taken up to 18 years ago, e.g with my first digital camera, a Canon 10D, and therefore imported originally into probably LR2.  Others taken in the intervening years came into successive Lightrooms having been taken with better and better cameras.  How will the latest LR Classic handle these?  If I ensure they are handled now under the current process, will they be handled using Prophoto?

I understand that no printer or paper will cope with Prophoto, hence the need to soft proof, which I do.  But how do I know what my printer and papers are using?  Are my images being rendered in Adobe RGB or SRGB?

Can anyone clear the fog of incomprehension?

Best wishes,

Jonathan
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digitaldog

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Re: Prophoto, Adobe RGB and SRGB
« Reply #1 on: February 22, 2022, 08:51:24 am »

Short answer; Only devices, or systems, that render color have a color gamut. Digital cameras do not have a color gamut (they have a color mixing function). Same with scanners. Dr. Roy S. Berns from RIT stated, in Billmeyer and Saltzman’s Principles of Color Technology: "Color gamut: Range of colors produced by a coloration system." Color gamut applies to systems that produce color (Printers, TVs Displays, projector) and color spaces as well.
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Jonathan Cross

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Re: Prophoto, Adobe RGB and SRGB
« Reply #2 on: February 22, 2022, 09:10:04 am »

Thanks Andrew.  I should have realised that the sensor just outputs RGB values from the pixels, presumably to the bit depth for that camera.  In my case I guess it is 14 bit.


There are still several other questions in my post.  I should have written that I print from all of LR, Photoshop, and Canon Print and Layout used as a plug-in. If you have any thoughts I would appreciate. 

Best wishes,

Jonathan

PS I contacted an organisation in the UK re a custom profile for Ilford GFS as a generic one did not appear for my printer on Ilford's website.  Ilford said this was because my printer was released after GFS was withdrawn.  I subsequently found one on their website - one of life mysteries!  Anyway, in their reply, the organisation, Colour Profiles, referred me to your document
http://digitaldog.net/files/PrintingTargetsCSUtility.pdf

Your fame spreads!

 
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Rand47

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Re: Prophoto, Adobe RGB and SRGB
« Reply #3 on: February 22, 2022, 10:57:57 am »

“Funny you should mention that…”

It just so happens that the just released video on PhotoPXL, with Dan Steinhardt and Jeff Schewe talks about color spaces, cameras, printers, vis-a-vis color gamut:

https://www.youtube.com/watch?v=sLVOaNhw65Q

I’ve learned a ton from Jeff Schewe and our own venerable Andrew Rodney.   I think you’ll find this video addressing, more or less, some of the issues you’ve raised.  Nice visuals from ColorThink along with it to illustrate.

Rand
« Last Edit: February 22, 2022, 11:02:54 am by Rand47 »
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digitaldog

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Re: Prophoto, Adobe RGB and SRGB
« Reply #4 on: February 22, 2022, 11:57:24 am »

The underlying color space for processing in Adobe raw applications is a variant of ProPhoto RGB. So I'd (I do) simply render into ProPhoto RGB in 16-bit and move from there.
No printer can even print the entire color gamut of sRGB. But there are printers who's color spaces are shaped such that a big RGB Working Space is necessary so colors you can capture and output do not clip, hence again, ProPhoto RGB.
The Dano and Schewe video is needed a good one and I recommend you watch it.
Of, you can also watch this and try the testing process either with the supplied image or your own:

The benefits of wide gamut working spaces on printed output:

This three-part, 32-minute video covers why a wide gamut RGB working space like ProPhoto RGB can produce superior quality output to print.

Part 1 discusses how the supplied Gamut Test File was created and shows two prints output to an Epson 3880 using ProPhoto RGB and sRGB, how the deficiencies of sRGB gamut affect final output quality. Part 1 discusses what to look for on your own prints in terms of better color output. It also covers Photoshop’s Assign Profile command and how wide gamut spaces mishandled produce dull or oversaturated colors due to user error.

Part 2 goes into detail about how to print two versions of the properly converted Gamut Test File file in Photoshop using Photoshop’s Print command to correctly setup the test files for output. It covers the Convert to Profile command for preparing test files for output to a lab.

Part 3 goes into color theory and illustrates why a wide gamut space produces not only move vibrant and saturated color but detail and color separation compared to a small gamut working space like sRGB.


High Resolution Video: http://digitaldog.net/files/WideGamutPrintVideo.mov
Low Resolution (YouTube): https://www.youtube.com/watch?v=vLlr7wpAZKs&feature=youtu.be
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Jonathan Cross

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Re: Prophoto, Adobe RGB and SRGB
« Reply #5 on: February 22, 2022, 05:52:12 pm »

Thanks. Yes I have seen the PhotoPXL  video and yes it is good.

Jonathan
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Rhossydd

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Re: Prophoto, Adobe RGB and SRGB
« Reply #6 on: February 22, 2022, 06:17:11 pm »

I have historic RAW images in my LR catalogue that were taken up to 18 years ago, e.g with my first digital camera, a Canon 10D, and therefore imported originally into probably LR2. ...... How will the latest LR Classic handle these?  If I ensure they are handled now under the current process, will they be handled using Prophoto?

 I should have realised that the sensor just outputs RGB values from the pixels, presumably to the bit depth for that camera.  In my case I guess it is 14 bit.
My understanding is that Lightroom has always used it's version of ProPhoto since the start, so good since day 1.
The 10D actually had a 12bit RAW capture, which was good for the time and still offers a lot.

One of the joys of digital photography is that improvements in software, in this case raw conversion, have also been applicable to old files as well as new. The latest process version will get more out of 10D files than was possible when the camera was new. The latest versions of Photoshop have also delivered better upsizing too. There's also better noise reduction products available both at raw level (DOX Photo Lab 5 Elite) or in rendered files with tools like Neat Image or Topaz.
You can go back to old files and get better results from them than was ever possible at the time the photos were first taken. Quite a win really.
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William Walker

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Re: Prophoto, Adobe RGB and SRGB
« Reply #7 on: February 23, 2022, 09:47:15 am »


No printer can even print the entire color gamut of sRGB.


Andrew, at around the 10:30 mark, Dan says something like, "for about ten years, Epson Professional Printers have been able to print wider than Adobe RGB..."

What does he mean by that?
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digitaldog

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Re: Prophoto, Adobe RGB and SRGB
« Reply #8 on: February 23, 2022, 09:53:45 am »

Andrew, at around the 10:30 mark, Dan says something like, "for about ten years, Epson Professional Printers have been able to print wider than Adobe RGB..."

What does he mean by that?
There are indeed some areas of the printer color space that fall outside Adobe RGB (1998) gamut.
There are indeed some areas of sRGB that fall outside the color space of the printer. Easy to see when plotted in 3D.
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Doug Gray

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Re: Prophoto, Adobe RGB and SRGB
« Reply #9 on: February 23, 2022, 10:21:17 am »

Andrew, at around the 10:30 mark, Dan says something like, "for about ten years, Epson Professional Printers have been able to print wider than Adobe RGB..."

What does he mean by that?

Printer colorspaces, like the smaller sRGB and larger Adobe RGB 1998, are 3 dimensional. However, they are very different shapes. Because of that there are parts of sRGB that can't be printed as well as portions of printer colorspaces that can be printed but can't be displayed in Adobe RGB 1998.

Edited to add: This is redundant to what Andrew just posted before me. Sorry Andrew, I should have refreshed the thread before posting this.

All of which is why softproofing is so useful. Especially if you have a lightbox that is set up with an illuminant that matches that of the display and the display is a wide gamut type.

Andrew's video's tend to be more tutorial and do a good job of explaining what people can expect to encounter printing and converting from different colorspaces.
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Rand47

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Re: Prophoto, Adobe RGB and SRGB
« Reply #10 on: February 23, 2022, 10:32:03 am »

Quote
Andrew's video's tend to be more tutorial and do a good job of explaining what people can expect to encounter printing and converting from different colorspaces.

You can say that again.  Andrew’s videos, and the downloadable files for “self testing,” have been super valuable for me.  I hear / see what he’s talking about in the videos, then do the prints at home from the various color space options and see the significant difference a the large working color space can make.   They’re very well thought out and executed. 

The Jeff and Dan show is more entertainment-like information, but still valuable - especially perhaps for those just being introduced to the “whole idea.”  And I learned something “new” about L* meaning “lightness” rather than “luminosity” - which may be a distinction without a difference, but accuracy in terminology is important, too.

Rand



Rand
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digitaldog

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Re: Prophoto, Adobe RGB and SRGB
« Reply #11 on: February 23, 2022, 11:18:06 am »

Luminosity is a measure of the total radiant energy from a body. It has nothing to do with what a human observer perceives but rather describes the total radiant energy, such as watts/second of a source (the surface of a radiating object like a display). In Photoshop, the layer mode called luminosity is not what's happening here (I was told its something like the "Luma" which is an old TV RGB transform)
Lightness is a perceptually scaled component of color, the axis seen in Lab (Lstar) from light to dark. It IS the L in HSL. 
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Rand47

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Re: Prophoto, Adobe RGB and SRGB
« Reply #12 on: February 23, 2022, 11:49:56 am »

Luminosity is a measure of the total radiant energy from a body. It has nothing to do with what a human observer perceives but rather describes the total radiant energy, such as watts/second of a source (the surface of a radiating object like a display). In Photoshop, the layer mode called luminosity is not what's happening here (I was told its something like the "Luma" which is an old TV RGB transform)
Lightness is a perceptually scaled component of color, the axis seen in Lab (Lstar) from light to dark. It IS the L in HSL.

Yes sir!  I love it when I learn something new, or have a misapprehension corrected.

Rand
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Chris Kern

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Re: Prophoto, Adobe RGB and SRGB
« Reply #13 on: February 23, 2022, 12:55:32 pm »

The Jeff and Dan show is more entertainment-like information . . .

Definitely worth watching if only to see Professor Schewe demonstrating comparative color spaces with a plastic Hoberman sphere.

Doug Gray

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Re: Prophoto, Adobe RGB and SRGB
« Reply #14 on: February 23, 2022, 01:02:54 pm »

Luminosity is a measure of the total radiant energy from a body.

It's the rate of total radiant energy (Joules per second). Alternatively, it can be described as the radiant power (watts). An example of how inappropriate the term is re vision, the luminosity of a human at night is similar to that of a 100 watt, incandescent lamp that is on. This is because the human's luminosity is in IR and long IR and not visible.

/physiscsnerd
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digitaldog

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Re: Prophoto, Adobe RGB and SRGB
« Reply #15 on: February 23, 2022, 01:06:00 pm »

It's the rate of total radiant energy (Joules per second).
It has nothing to do with what a human observer perceives but rather describes the total radiant energy, such as watts/second of a source (the surface of a radiating object like a display).

https://socratic.org/questions/is-one-joule-per-second-equivalent-to-one-watt
One Watt is defined as 1 Joule of energy per 1 second.
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Doug Gray

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Re: Prophoto, Adobe RGB and SRGB
« Reply #16 on: February 23, 2022, 01:21:24 pm »

https://socratic.org/questions/is-one-joule-per-second-equivalent-to-one-watt
One Watt is defined as 1 Joule of energy per 1 second.

That's right. Both terms are equivalent. Adding "rate" is what turns energy (Joules) into power (Joules per second).
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Jonathan Cross

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Re: Prophoto, Adobe RGB and SRGB
« Reply #17 on: February 23, 2022, 01:44:47 pm »

Having watched the excellent video on Photpxl, already mentioned, I have checked my LR Classic (v11.2) and Photoshop (v23.2).  I am happy that LR uses Prophoto in the Develop module and is 16 bit.  In Photoshop the default was Adobe RGB and 8 bit so I had to change these and check the changes in Preferences/Camera Raw, Edit/Color settings, Edit/Assign Profile and Image/Mode.

Jonathan



 
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digitaldog

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Re: Prophoto, Adobe RGB and SRGB
« Reply #18 on: February 23, 2022, 02:09:04 pm »

I am happy that LR uses Prophoto in the Develop module and is 16 bit.
To nit-pick and be clear, both ACR and LR's processing engines use a variant of ProPhoto RGB. Same color gamut (chromaticity values), a 1.0 TRC ("gamma"), unnamed and not thus ProPhoto RGB.
In Lightroom Classic, outside of Soft Proofing, the RGB numbers are Melissa RGB; same color gamut, 2.2 TRC like sRGB.
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digitaldog

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Re: Prophoto, Adobe RGB and SRGB
« Reply #19 on: February 23, 2022, 05:01:33 pm »

Not to hijack this discussion, but what effect do the different gammas have on our perception? Maybe there's a better way to frame my question.
Gamma where? In a Working Space, for display calibration?
In color-managed app's, the short answer is, virtually none.
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