civilized ku # 1151 ~ autumn flowers
Tuesday, October 18, 2011 at 01:33PM 
Backyard Autumn flowers ~ Au Sable Forks, NY - in the Adirondack PARK • click to embiggen
LAB color space - b Channel curve • click to embiggenSven W asked, re: civilized ku # 1149:
... did the image for this post require much in the way of post-processing to get the colours right? I think you're mentioned before that you often need to tweak the greens in some way?"
The picture, yard and garage in the rain, Sven is referring to required just a bit more processing than is usually my norm. I attribute that to the fact that the scene had very saturated color due to the rain. This natural saturation + that of my camera sensor (E-P1/E-P2) created, to my eye and sensibilities, a overall yellow bias* to the picture (as viewed in my RAW conversion software on my calibrated screen).
VERY IMPORTANT CAVEAT: My camera was an Oly E-P2. My camera WB was set to "CLOUDY". My monitor is calibrated using a Gretagmacbeth Eye-One device. My RAW conversion software is RAW Delveloper**, and my primary processing software is Photoshop. Exactly where in all of these variables the yellow bias originates is an open question. Most likely it is inherent in the Oly sensor and color engine. In any event, the manner in which I process my files, respective to yellow, should be taken only as a general guide. Your mileage may vary. END OF CAVEAT
In any event, using RAW Developer in LAB color space (and after making a minor WB adjustment), I made a curve in the b Channel (blue/yellow content) like that seen in the above screen grab. That curve illustrates a curve typical of the one I regularly use for yellow correction and, on occasion, red correction (in the b Channel). That is, I (important! important! important!) anchor the curve at the mid point and then add a point approximately 1/5 of the way down the curve. I use that point to make my adjustment by dragging it up - in the case of the image in the curve illustration picture, I moved it up a very small amount. FYI, the image on the right is the before, on the left is the after.
In the case of the yard and garage in the rain picture, I moved it up a fair amount more, the amount determined by real-time viewing of the change in the picture as seen on my calibrated monitor. I just moved the point until the color looked right. It is worth noting that I also performed the same correction, using the same curve structure and procedure, for a red adjustment (albeit to a much more subtle degree) on the a Channel (green/magenta content) on the yard and garage in the rain picture.
All of that said, some might ask why I am making adjustments to yellow when Sven asked about adjustments to green. That's simply because yellow + blue = green. The resultant shade of green is dependent upon the mix of the two colors. My experience, taking into account all the previously mentioned variables, has demonstrated that there is too much yellow in my greens which creates a rather homogenized green, albeit "pleasantly" rich. Too rich for my blood.
NOTA BENE: making color adjustments in LAB color space is a very different and much more powerful manner of making adjustments as opposed to making them in RGB color space. I can't get all techincal on you why this is so - it would require about a zillion words, make your head spin, and give you a massive headache. Suffice it to state, what I have tried to do is give a down-and-dirty approach to making these type of adjustments in LAB. If you want to learn more about LAB color space, try here or use your google machine to find other sources.
*I do NOT view this yellow "bias" as a flaw in the Oly sensor / color engine - Oly is universally respected for their very pleasant color results (jpegs right out of the camera). Rather, it is just Oly's take on their idea of color flavor - all camera makers have one. Some might find Oly's take on color flavor right up their alley. I do not.
**RAW Delveloper is a MAC OS X optimized RAW conversion software. It creates, via its own custom demosaicing algorithms, wonderful film-like files. The software has all the tools one could ask for, including the capability of performing color adjustments (curves), contrast/tonal adjustments (curves), and hybrid sharpening in LAB color space. Another real plus for me is the fact that the program is not a memory hog - all it does is RAW conversion processing.
Reader Comments (5)
Very interesting post. You said "My camera WB was set to "CLOUDY"."... why is that relevant if you are working in RAW?
When I click on Autumn Flowers to see the larger version a different photo is displayed.
Anil - thanks for the heads up. It's fixed.
Thanks for the explanation.
RAW Developer sounds great -- too bad it's not available on Windows boxes. I've also noticed that your images have a look that is part way between digital and film and thought it might be the Olympus processing.
As for too much yellow in the greens, I can now see the same affliction in my images. I see can my images aren't quite right, but I can't always determine why ... your blog is very helpful in helping me see.
My simple way of dealing with this problem is to create a hue/saturation adjustment layer, drop the yellow saturation and mask in the greens. This looks better but don't ask me whether or not my greens are now the correct hue!
How do you handle the lack of lens distortion correction in Raw Developer? Many MFT lenses have significant barrel distortion and chromatic aberration that's expected by the manufacturer to be corrected in software. The Olympus raw software, Lightroom/ACR, and Aperture/iPhoto all "understand" how to correct distortion.