sRGB, Adobe RGB, and ProPhoto RGB: A technique to SEE the differences

Started Nov 24, 2012 | Discussions thread
Vernon D Rainwater
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Re: sRGB, Adobe RGB, and ProPhoto RGB: A technique to SEE the differences
In reply to technoid, Nov 24, 2012

technoid wrote:

The endless discussion, much of it quite informed, about gamut size differences and "lost" colors and actually determining where the differences matter suggested an approach that anyone can apply to their photos in order to see the impact of smaller gamuts and especially sRGB, a relic from the CRT days and their limited RGB phosphors.

Here's an easy way, if you have RAW files and use PhotoShop, to see the actual impact. Both on monitors and on prints.

First, especailly if you have a standard gamut monitor, select the "Desaturate images 20%" option in preferences. While this slightly reduces viewing color saturation it effectively increases the range you can see color change in a standard monitor and allows you to see differences in, say, Cyan that exceed sRGB but not wider gamuts without spending the money for a wide gamut monitor. It may also be useful if you have a wide gamut monitor and are curious where Adobe RGB clips ProPhoto colors.

It appears by the above mentioned "Desaturate images 20%" option in preferences that the image(s) have to first be "degraded" in order to be able to use the added details in order to "see" the differences in different Color types.  Then, evidently it is somewhat difficult (if at all possible) to be able to see any real differences in the three types, when printed.  Seems there is perhaps a few color types for which is practical to see the difference on the Monitor but less versatile with the Photo Printing.

Sometimes, it seems we may be trying to force the practical use of the color types then find there are few (if any) printers that are capable of utilizing (and printing) the added color types.

1. Convert the raw image normally but use 16 bit ProPhoto RGB as the target space.

2. In PhotoShop select image duplicate twice. You now have three identical images. Label one ProPhoto, another sRGB, and the last AdobeRGB.

3. On the sRGB labeled image convert to sRGB, then convert again to ProPhoto RGB using RC without blackpoint correction for both conversions.

4. On the AdobeRGB labeled image convert to Adobe RGB, then convert again to ProPhoto RGB using RC without blackpoint correction for both conversions.

5. On all three images put a small text label in a corner to identify the gamut the image was clipped to. I use a single letter, P, A, and S. Now merge the text and image layers. This process makes it easier to identify which image is showing up on a layer stack.

6. Now copy the AdobeRGB image and the sRGB image to separate new layers on the ProPhoto image. Label each of the three layers for easy reference.

7. Close the Adobe and sRGB images. They are no longer needed.

Now, by clicking the visibility "eye" for each layer you can turn on and off the different, gamut clipped images.

This can be further extended to see what the impact on a print would be by first selecting the printer profile in soft proofing.

This is a good way to determine exactly what is lost or, more commonly, not lost by using gamuts other than ProPhoto. Keep in mind that people can't actually instantly swap actual prints so subtle changes that might jump on using this would be much harder to see in photos. Try showing the clipped images side by side. It's much harder to see the differences unless they are fairly big like a flower closeup or brigthly colored industrial product.

One way to bring out differences is to increase color saturation in your photos. If you do that for artisitic reasons you may well see bigger differences.

Try this and share your experiences.

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Vernon...

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