ProPhoto RGB

<p>I have just learned about ProPhoto RGB. I'd appreciate your comments about this color space. Do you use it? How do you like it? Do you perceive the wider range of reds, greens, and blues it provides to be a benefit in landscape images?</p>

<p>Prophoto RGB is a better fit with the color space available in RAW images, compared to sRGB or Adobe RGB which clip to some extent. Prophoto RGB gives you a more room to adjust colors without banding, but little else. Since RAW images are the digital equivalent of negatives, it makes sense to get all you can out of them, regardless of limitations further down the line.</p>

<p>You will not see any difference on a monitor or in a print, which have a smaller gamut than Prophoto RGB. Few monitors have a color depth greater than 8-bit, and most are 6-bit with dithering. Printers seem to fall between sRGB and Adobe RGB in gamut, but comparisons are complicated between RGB monitors and CMYK ink sets.</p>

<p>Never submit Prophoto image files to a client without specific arrangements to that effect. Images will look drab and colors may be distorted on a non-CMS compliant computer.</p>

<p>Interesting. I have been reading <em>Real World Camera Raw, </em>by Bruce Fraser and Jeff Schewe and they recommend it for Camera RAW as well. Are you saying that I should convert back to Adobe RGB in printing and in presenting images to others? Thanks, Edward for your help.</p>

<p>If you have a display that is wider by some degree than sRGB you'll be able to get noticeably richer yellows, oranges and cyans in ProPhotoRGB. To test this just create a new CMYK file in Photoshop, open the color picker and create a 100% cyan swatch fill, convert to ProPhotoRGB then convert to sRGB and watch the color shift.</p>

<p>I get these types of shifts with the other colors mentioned shooting flowers in Raw and processing in ACR in ProPhotoRGB. Once I convert to sRGB the colors slightly lose their vibrance.</p>

<p>If you're doing your own printing, there's no reason for a file to leave ProPhoto. Color management will handle it, and even an inexpensive inkjet photo printer will exceed both sRGB and Adobe RGB in some areas.</p>

<p>If you're going to a lab, in that case you'll probably need to convert it down to Adobe RGB if not sRGB.<br /> If the file's going to a client or the web, convert to sRGB or bust.</p>

<p>I stopped using it. The labs I send my photos to do not use it. Any photos posted on the web do not use it. It is a better profile than AdobeRGB and sRGB? Yes! But what is the point of using it when the real world does not or even cares about it. </p>

<p>Bill</p>

 

<p>Its the only encoding color space I use for export FROM Raw data, see:<br>

<a href="http://www.adobe.com/digitalimag/pdfs/phscs2ip_colspace.pdf">The Role of working spaces in Adobe applicaitons</a></p>

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<p>I stopped using it. The labs I send my photos to do not use it.</p>

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<p>Yes, Unfortunately there are labs that don’t have a clue about color management! </p>

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<p>But what is the point of using it when the real world does not or even cares about it.</p>

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<p>It gives you more headroom. Its a good starting point also. What you are saying is the equivalent of me saying, "well i only plan on putting these files on the web so i might as well resize my image to 640x480 right way and go with that throughout the process."</p>

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<p>But what is the point of using it when the real world does not or even cares about it.</p>

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If you want to get geeky....

All RGB working spaces are synthetically (defined from simple math values) built. They are all based on theoretical emissive output devices (displays). The do not behave like input and output color spaces which have unique kinks and idiosyncrasies. An example are just about any RGB output profile you have where RGB neutrals are not defined using equal values. R=G=B being a neutral is the behavior of synthetically created working spaces and that’s useful for editing images as well as archiving them (they are Quasi-Device Independent spaces although technically RGB isn’t device independent).

 

 

The shape of these man made constructed working spaces are very simple in shape. You often see them plotted 2-D as appearing like a triangle. The three points represent the RGB primaries and thus the size of the gamut. Keep this size and shape in mind and note that differing real world color spaces can be vastly different in both cases.

 

 

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.

<p>Well folks,</p>

<p>I looked into prophoto and decided to abandon using it.</p>

<p>1) No visual increase in output (screen or prints)<br>

2) 21% of the colors defined by the prophoto colorspace are imaginary. (i.e) beyond theoretical limits.</p>

<p>I just can't see the justification.</p>

 

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<p>It gives you more headroom.</p>

 

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<p>That would be a good thing if you could access that headroom...You can't; at least not all of it.</p>

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<p>1) No visual increase in output (screen or prints).</p>

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<p>Printed from what to what? </p>

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<p>2) 21% of the colors defined by the prophoto colorspace are imaginary. (i.e) beyond theoretical limits.</p>

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<p>I explained why above. The triangle has to grow proportionally. It is useful to know color numbers can be defined that don’t represent colors! If you can’t see em, they are not a color. </p>

<p>Right!</p>

<p>So; I personally can see no measurable gain by working within such a gamut when so many of the colors occur outside (real) colors.<br>

<em></em><br>

I've read all the tech gobbilty gook concerning this color space, I remain far from convinced.</p>

<p>Heck; I edit within the RGB space and convert to sRGB before output..and I still wonder why since I've also edited within sRGB with ZERO noticeable difference visually.</p>

<p>I find the point somewhat moot anyway as we work within undefined colorspace if we edit RAW images.</p>

<p>Is not output what we are concerned about anyway?</p>

We're concerned about preserving what can't be seen yet due to limits of current input, editing and output technology. You don't know exactly what's in that Raw image because the data is interpreted by current software and output on devices that are just as limited.

 

To get an idea how many possible viewable colors you are throwing away by working in sRGB make three duplicates of one image with one converted to sRGB, the other to AdobeRGB and the last to ProPhotoRGB. With each image click on the black foreground swatch in Photoshop's tool bar to bring up the Color Picker and click on the Red radio button. Note the differences you get in the greens and blues. To better compare take a screengrab of the Color Picker Green/Blue field for each image and once opened in Photoshop assign your display profile.

 

I get a more vibrant and rich variety of greens and blues in ProPhotoRGB compared to the others.

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<p>Heck; I edit within the RGB space and convert to sRGB before output</p>

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<p>Output to what devices? Many have gamuts that far exceed sRGB (and Adobe RGB for that matter). </p>

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<p>I find the point somewhat moot anyway as we work within undefined colorspace if we edit RAW images.</p>

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Maybe you do. The processing color space my Raw converter uses is ProPhoto RGB with a linear TRC (Gamma).

 

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<p>Is not output what we are concerned about anyway?</p>

 

 

 

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Yes but the point and facts are, the encoding color space before you output plays a role IN the output.

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<p>Yes but the point and facts are, the encoding color space before you output plays a role IN the output.</p>

 

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<p>I would be most interested in some references that will show prophoto's (visible) difference from a photographers point of view. (i.e) Prints.</p>

Kevin, so I'll assume, since you stress prints as the only important workflow pipeline in digital processing, what I said above didn't register or you didn't read it at all.

Lightroom (and other programs) use ProPhoto RGB internally, so many people are using it without knowing. Adobe RGB is obsolete. Recent museum standards recommend eciRGBv2 working space instead.

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<p>I would be most interested in some references that will show prophoto's (visible) difference from a photographers point of view. (i.e) Prints.</p>

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<p>Do you have a printer? Do you have one that exceeds sRGB and maybe even Adobe RGB (1998) like a modern Epson with K3 or even more, HDR inks? If so, you can do this all yourself as many of us have. The gamut maps in the referenced articles illustrate the big differences in gamut and resulting color clipping going from sRGB instead of ProPhoto to an Epson. But you can hopefully find images that are wide gamut too and print them for yourself. Of course, if all you shoot is brides in white wedding dresses or foggy landscapes, the scene gamut will be to small to see the results of the wider gamut encoding and output color space. But bottom line, testing this yourself is pretty darn easy. </p>

Andrew or others, do you have any comments on this? (recently posted to the Digicam forum)

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<a href="http://www.cdiny.com/ArticlesWhitePapers/ISO%20Standards%20for%20Museum%20Imaging_cdi_v1.0.pdf">Adopting ISO Standards for Museum Imaging</a>

<p>Bill, I read to page 7 and after a few too many historical and technicalities IMHO, I stopped. Specifically, besides the first 7 pages, and the fact some of us are not museums, what were you wondering about?</p>

Andrew, I was wondering what you and others think about eciRGBv2, which that paper recommends to replace AdobeRGB. Apparently it is similar to eciRGB but with L* gamma instead of 1.8 gamma.

<p>The European L* advocates have provided pretty much zero documentation of an advantage or peer review from the international color community as discussed March 2008 on the ColorSync list* and more recently here:</p>

http://luminous-landscape.com/forum/index.php?showtopic=38535&hl=Lstar

 

*You can search the archives under “L* workingspaces museum market..“ Both Lars Borg of Adobe‘s head color scientist and Chris Murphy have posts that at least provide salient arguments against both the idea of an L* gamma encoding for most work and the request for less rhetoric and more science from the proponents.

 

 

<p>Here's what I did. I use a Roland FJ50" plotter to print my Real Color Wheel. I found that if I use my own TRANSPARENT home made Tartrazine yellow ink I get more color into my prints. The opaque yellow that is standard ink for litho and inkjet mixes with the other sprayed colors so Yellow, magenta and cyan do not mix dark. More black ink is necessary to overcome this. I use less black in and get my full range of color. I always convert to USweb before printing an RGB image. My color wheel was made in CMYK so I don't have a RGB choice to convert from and I have a lot of ink application choices that can fix any RGB conversion problem. </p>