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Author Topic: Prophoto RBG  (Read 12698 times)
Mark F
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« on: August 15, 2008, 07:35:11 PM »
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In Michael's "Camera to Print" tutorial the point is effectively made that Prophoto RBG has a wider gamut than Adobe RBG and this translates into more information being available for prints. But I do not understand where Prophoto fits in the process. Is it used instead of Lightroom or Photoshop?  Is it  a RAW converter whose files are then exported to Lightroom or Photoshop?

Any guidance would be appreciated.

Mark
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Mark
MorganAdam
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« Reply #1 on: August 15, 2008, 09:00:43 PM »
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In both Photoshop and Lightroom you are allowed to set your default color space (part of your preferences). Instead of using Adobe RGB, you would set it to ProPhoto RGB.

If you've set the preferences correctly, when you import your RAW files into either program they will both use that color space. If you are only dealing with your own files (from import to printing) then, most likely, you won't have to think about it again.

There are top color experts on these forums (I'm not one of them). Do a search and you'll find more in-depth threads.
« Last Edit: August 15, 2008, 09:02:01 PM by MorganAdam » Logged
kbolin
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« Reply #2 on: August 15, 2008, 09:23:03 PM »
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In Michael's "Camera to Print" tutorial the point is effectively made that Prophoto RBG has a wider gamut than Adobe RBG and this translates into more information being available for prints. But I do not understand where Prophoto fits in the process. Is it used instead of Lightroom or Photoshop?  Is it  a RAW converter whose files are then exported to Lightroom or Photoshop?

Any guidance would be appreciated.

Mark
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A couple of points... it's RGB vs. RBG.  There are 3 main colorspaces for photo purposes (yes I know there are more but we'll leave it to 3 for the purposes of this thread).  
sRGB - appropriate and used for web images.
Adobe RGB - general use or photos that don't have a wide color gamut.
ProPhoto RGB - photo printing or those images that have a wide color gamut.

You'll want to read Michael's article on LL [a href=\"http://www.luminous-landscape.com/tutorials/prophoto-rgb.shtml]Understanding Prophoto RGB[/url]

Lightroom uses Prophoto RGB by default with an sRGB tone curve.  So as soon as you open a photo it will use the ProPhoto colorspace assuming you are shooting in RAW.  If you are shooting JPEG (not for me... sorry) then it will use the colorspace determined by your camera (sRGB or Adobe) if the option exists.

In Photoshop goto Edit >> Color Settings >> set your Working Space for RGB to sRGB, Adobe RGB, or ProPhotoRGB (recommended).

So much more to say but Michael's article will be a good start.

Hope this helps.

K
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Mark F
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« Reply #3 on: August 17, 2008, 09:06:48 PM »
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Found the article and it is, as you write, very helpful i think i have a better idea now. Thanks very much (and for the RBG misspelling too).

Mark


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A couple of points... it's RGB vs. RBG.  There are 3 main colorspaces for photo purposes (yes I know there are more but we'll leave it to 3 for the purposes of this thread). 
sRGB - appropriate and used for web images.
Adobe RGB - general use or photos that don't have a wide color gamut.
ProPhoto RGB - photo printing or those images that have a wide color gamut.

You'll want to read Michael's article on LL Understanding Prophoto RGB

Lightroom uses Prophoto RGB by default with an sRGB tone curve.  So as soon as you open a photo it will use the ProPhoto colorspace assuming you are shooting in RAW.  If you are shooting JPEG (not for me... sorry) then it will use the colorspace determined by your camera (sRGB or Adobe) if the option exists.

In Photoshop goto Edit >> Color Settings >> set your Working Space for RGB to sRGB, Adobe RGB, or ProPhotoRGB (recommended).

So much more to say but Michael's article will be a good start.

Hope this helps.

K
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Mark
Panopeeper
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« Reply #4 on: August 17, 2008, 09:58:06 PM »
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It must be great to have a ProPhoto capable printer.
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Gabor
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« Reply #5 on: August 18, 2008, 12:32:26 AM »
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Panopeeper,

no need to be sarcastic here...

No printer has the gamut to print ProPhotoRGB (yet), although many printers can print nowadays into areas of color gamut that can be described by AdobeRGB (and not sRGB). But this is beside the point.

Read carefully some of the points made here

http://www.luminous-landscape.com/tutorial...photo-rgb.shtml

to understand the benefits of using a "broad" color gamut. Essentially keeping all of the available data that your camera's raw file is able to provide and then to render it CONTROLLED into the gamut of the media (e.g. paper) that you want to print it on.

But in case you never found any fault in your prints (regarding rendering of colors) then you might as well stick to sRGB or AdobeRGB.
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digitaldog
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« Reply #6 on: August 18, 2008, 09:01:26 AM »
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Panopeeper,

no need to be sarcastic here...

No printer has the gamut to print ProPhotoRGB (yet)..

Although there will NEVER be a printer that can produce ProPhoto RGB considering two primaries fall outside human gamut (vision).

For those looking for more info on ProPhoto or LR:
http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf
http://www.ppmag.com/reviews/200701_rodneycm.pdf
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Andrew Rodney
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Panopeeper
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« Reply #7 on: August 18, 2008, 10:38:18 AM »
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Read carefully some of the points made here

http://www.luminous-landscape.com/tutorial...photo-rgb.shtml

to understand the benefits of using a "broad" color gamut
I am converting most of my raw images in 16bit ProPhoto TIFF, but I am not reasoning this with the printer.
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Gabor
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« Reply #8 on: August 19, 2008, 10:54:59 AM »
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Another good read
Marc

http://www.josephholmes.com/profiles.html
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Marc McCalmont
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« Reply #9 on: August 21, 2008, 08:55:20 AM »
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Panopeeper,

no need to be sarcastic here...

No printer has the gamut to print ProPhotoRGB (yet), although many printers can print nowadays into areas of color gamut that can be described by AdobeRGB (and not sRGB). But this is beside the point.

Read carefully some of the points made here

http://www.luminous-landscape.com/tutorial...photo-rgb.shtml

to understand the benefits of using a "broad" color gamut. Essentially keeping all of the available data that your camera's raw file is able to provide and then to render it CONTROLLED into the gamut of the media (e.g. paper) that you want to print it on.

[{POST_SNAPBACK}][/a]

Panopeeper must be taking lessons from Jeff Schewe  . However, his statement sums up nicely some of the common objections to ProPhotoRGB: why waste space on colors that you can't see or print. The answer is to gain access to colors that you can see or print. Digidog's reference to an article on the Adobe site by Jeff Schewe and Bruce Fraser contains a 2D graphic demonstrating the gamuts of the horse shoe shaped CIE space (that contains the colors of human vision) and various other spaces including the gamut of Epson matt photopaper. Some yellows of the matt paper are outside of the aRGB gamut and would be lost if your working space were aRGB.

Glossy papers and the newer inks have a considerably wider gamut than the matt paper. The 2D graphics show the gamuts at only one luminance (usually L=50). These newer papers and inks have greens at relatively low luminance that are well outside of aRGB. To view these gamuts one needs a 3D gamut program such as Colorthink or Gamutvision. One can also use these programs to examine the gamut of your monitor. Most monitors can only display the gamut of sRGB, but a few newer ones can cover the gamut of aRGB. This means that with ProPhoto you may have colors that can not be viewed on screen or with soft proofing. This may present problems, but you can still use the gamut warning in Photoshop to edit these colors for the best print appearance rather than having them lost in a smaller space.

If you don't have one of these programs, Michael gives several 3D gamut plots in his article and [a href=\"http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html]Bruce Lindbloom's site[/url] has a demo viewer.

Bill
« Last Edit: August 21, 2008, 09:00:13 AM by bjanes » Logged
digitaldog
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« Reply #10 on: August 21, 2008, 09:03:26 AM »
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However, his statement sums up nicely some of the common objections to ProPhotoRGB: why waste space on colors that you can't see or print.


Sorry for this copy and paste for those who've see it:

There are way, way more colors that can be defined in something like ProPhoto RGB than you could possibly output, true. But we have to live with a disconnect between the simple shapes of RGB working space and the vastly more complex shapes of output color spaces to the point we're trying to fit round pegs in square holes. To do this, you need a much larger square hole. Simple matrix profiles of RGB working spaces when plotted 3 dimensionally illustrate that they reach their maximum saturation at high luminance levels. The opposite is seen with print (output) color spaces. Printers produce color by adding ink or some colorant, working space profiles are based on building more saturation by adding more light due to the differences in subtractive and additive color models. To counter this, you need a really big RGB working space like ProPhoto RGB again due to the simple size and to fit the round peg in the bigger square hole. Their shapes are simple and predictable. Then there is the issue of very dark colors of intense saturation which do occur in nature and we can capture with many devices. Many of these colors fall outside Adobe RGB (1998) and when you encode into such a 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.
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Andrew Rodney
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« Reply #11 on: August 21, 2008, 09:05:34 AM »
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Digidog's reference to an article on the Adobe site by Jeff Schewe and Bruce Fraser ....

By whom? Sorry, it was a lot of work ;-)
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Andrew Rodney
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« Reply #12 on: August 21, 2008, 03:23:59 PM »
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To counter this, you need a really big RGB working space like ProPhoto RGB again due to the simple size and to fit the round peg in the bigger square hole.[a href=\"index.php?act=findpost&pid=216454\"][{POST_SNAPBACK}][/a]
Actually you need a really big working space if you go the Adobe way... no? If you work e.g. with Capture One you can embed the camera profile. And it contains all the colors the camera can capture - and none more. (Actually it contains the colors measured by Phaseone... okay). So the camera profile is big enough and at the same time not too big. And just contain real colors.
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digitaldog
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« Reply #13 on: August 21, 2008, 03:37:31 PM »
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Actually you need a really big working space if you go the Adobe way... no? If you work e.g. with Capture One you can embed the camera profile. And it contains all the colors the camera can capture - and none more. (Actually it contains the colors measured by Phaseone... okay). So the camera profile is big enough and at the same time not too big. And just contain real colors.
[a href=\"index.php?act=findpost&pid=216544\"][{POST_SNAPBACK}][/a]

There's a processing color space in all Raw converters and that's what you're pretty much getting with Adobe Raw processors (ProPhoto primaries, linear encoding).

Plus you really DO NOT want to do editing in input or output color spaces, they are not well behaved.

There's no such thing as unreal colors. If you can't seem em, they are not a color.
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Andrew Rodney
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« Reply #14 on: August 21, 2008, 03:44:53 PM »
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Plus you really DO NOT want to do editing in input or output color spaces, they are not well behaved.
I want. The camera profiles in C1 all have a neutral gray axis. What I do is embedding the camera profile than edit the image in Photoshop - all on layers - while ECI RGB V2 is set as proof color (with color warning). So I do optimize with regard to ECI RGB V2 but preserve the 16bit TIF in the camera profile on the bottommost layer. This (fat) file goes to archive (I do not trust in RAW formats or DNG and this is why I want to store TIFs).
But I'm prepared to optimze my workflow ;-)


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There's no such thing as unreal colors. If you can't seem em, they are not a color.[a href=\"index.php?act=findpost&pid=216546\"][{POST_SNAPBACK}][/a]
All the high satureated blues of ProPhoto are on L* 0... which is black, no?
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digitaldog
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« Reply #15 on: August 21, 2008, 03:56:54 PM »
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I want. The camera profiles in C1 all have a neutral gray axis.

Begging the question about what these so called profiles are really defining or fingerprinting! The camera capture itself?

Considering such capture devices don't really even have a color gamut, one wonders what was used to define them.


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All the high satureated blues of ProPhoto are on L* 0... which is black, no?

There are values which plot outside the spectrum locus no question.

I think this post by Karl Lang sums it up best:
http://luminous-landscape.com/forum/index....&view=getnewpos
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Color, is a perceptual property. So if you can't see it it's not a color. Color is not a particular wavelength of light. It is a cognitive perception that is the end result of the excitation of photoreceptors followed by retinal processing and ending in the visual cortex. We define colors based on perceptual experiments.

A coordinate in a "colorspace" outside the spectrum locus is not a color. We often refer to these as "imaginary colors" but this is by and large also erroneous (you can't map an imaginary color from one colorspace to another as the math (and experimental data) for each colorspace breaks down outside the spectrum locus.

No one sees IR. Most IR LEDs have minor output in visible wavelengths as well as IR.


Karl Lang
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Andrew Rodney
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« Reply #16 on: August 21, 2008, 04:08:02 PM »
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Considering such capture devices don't really even have a color gamut, one wonders what was used to define them.
As always if you are profiling a camera - color target shots. As far as I know they take the average of three shots from three camera models. So the camera profiles are based on the target captures (daylight and tungsten). Than they edit the profiles.
Me I checked BasICColor Input... but for a P45 the profiles provided by Phaseone are quite good, so I didn't really benefit of my own profile.

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I think this post by Karl Lang sums it up best:
http://luminous-landscape.com/forum/index....&view=getnewpos
[a href=\"index.php?act=findpost&pid=216550\"][{POST_SNAPBACK}][/a]
Thanks!
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digitaldog
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« Reply #17 on: August 21, 2008, 06:10:12 PM »
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As always if you are profiling a camera - color target shots.

A "fatal flaw" (assumption) in the process.

For fun, one could shoot an image of say a red laser. We know its at the edge of human gamut (its a pretty saturated primary). Then compare that to the red primary gamut edge in a target and the subsequent profile built. I suspect there's a huge difference/disconnect between the two.

Does anyone really think we could build a target that represent a gamut possibilities of what the camera captures?
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Andrew Rodney
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« Reply #18 on: August 21, 2008, 06:18:42 PM »
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Does anyone really think we could build a target that represent a gamut possibilities of what the camera captures?[a href=\"index.php?act=findpost&pid=216574\"][{POST_SNAPBACK}][/a]
Definitely NOT... this would be a printer gamut :-|
The target colors are just "track-points" and the profile will be extrapolated according to certain complex values (this is why camera pofiles mostly are "bloated" - but Phaseone edit them in a good way... at least in a well working way).
Check e.g. BasICColor Input (should be "Color Eyes" in the US) and you will get an idea of it.
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digitaldog
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« Reply #19 on: August 21, 2008, 06:42:27 PM »
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The target colors are just "track-points" and the profile will be extrapolated according to certain complex values (this is why camera pofiles mostly are "bloated" - but Phaseone edit them in a good way... at least in a well working way).

So a big guess?

So the profile has no idea about the illuminant under which the scene is captured, it assumes one.

Now we have a gamut extrapolated from a target. A far cry from how profiles for both scanners (the gamut of the target being the thing we're trying to capture) or the print (the colorants actually measured along with the paper white).

You'll excuse me if I am skeptical that this process is defining device behavior.
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Andrew Rodney
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