Spring Flowers using the Sigma 24-105mm F4 DG (OS) HSM and the the Sigma 70mm F2.8 EX DG Macro lens

Started Jun 8, 2014 | Discussions thread
xpatUSA Forum Pro • Posts: 11,785
Re: The limits to gamut

xpatUSA wrote:

Nancy and Pete Spader wrote:

<snip>Since we do not know exactly where they are it is still worth pushing the envelope as far as we can!

<snip> For this purpose, I find ColorThink invaluable but it does cost a buck or two. In their 3D view, it is easy to see over-saturated colors crammed up against a standard color space boundary and, by experimentation, back off the ProPhoto working space saturation, re-save as sRGB until the crammed color(s) in ColorThink spread out a bit. I find that as little as about -0.3 on the saturation slider does the job for many 'saved as sRGB' shots. The main point here is having the feedback from ColorThink rather than gazing at an image and wondering.

Today I found a sunflower X3F with highly saturated yellows. I opened it in ProPhoto working space and saved as four sRGB jpegs with saturations of 0, -0.3, -0.5 and -1.0. The jpeg output files looked like this:

View original size to see which is which . .

Then I opened them all simultaneously in ColorThink's 3D Lab view and also opened the sRGB color space for comparison:

See the plot colors for which is which, if it's not obvious

We see that, at 0 sat., the yellows are crammed hard to the right. At -0.3, a slight improvement especially lower down. At -0.5, all is well! At -1, the image is obviously de-saturated too much. Of the four images I would used the -0.5 sat. and upped the sat. a bit in post. Or, I would gone to SPP and tried -0.4 saturation.

Now lets look for any hue shifts by using the 2D view:

As the 0 sat. image yellows head up the yellow(ish) axis we see that they take a sharp left and head off to true yellow on the boundary line. That is to say, there is a significant color change which we may not like. The -0.3 sat shifts similarly at the boundary, albeit not so bad. Again, the -0.5 image would be my choice for final processing.

I can put the X3F up on my site if anyone wants to play - it's a LO res SD10 snapshot - not Merrill-huge 

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