I came across a method of processing recently as exercised and flaunted by Guy Gowan...I had heard of him before and got the usual "he changed the way I process images" comments. Now I can see why. I had seen excerpts of what he had done so I could work out his methodology.
Below are 2 images - your typical before and after. Nothing special just a club outing to Leenane, Co. Galway during 2010. It was taken handheld using the Panasonic Lumix LX3 in low light. The image was about 2 stops underexposed and had a green cast (as you can see).
Before:
After:
In Lightroom I raised the Exposure about 1+2/3rds of a stop. I didn't worry about the bright sections to the right side as the Histogram said nothing was blown - I could have balanced it but that wasn't the intention of this exercise.
So exporting to Photoshop I got to work on the colour cast. I saw by the Histogram (expanded version) that the greens were excessive so I added a photo filter magenta to bring the colour back...about 25% with Luminosity preserved. I tried to boost the blues a little but this served no real purpose so I left it as it was. A bit of noise reduction then with an interesting method of contrast boost.
The contrast boost utilises firstly a Levels layer where Auto is selected with "Enhance Monochromatic Contrast" checked in Options and 0% clipping. Then an alpha channel from the RGB Channel placed on a Curves adjustment as a mask for highlights was run. This was on a 50%/50% point and dragged down by 10%. Then I ran a levels adjustment on the Alpha Channel generated mask (Alt-L) and moved the sliders in to just past the edge of the histogram edges.This layer was duplicated, the mask was inverted and the Shadows were increased by 5% by using the same method but not placing a Levels adjustment on the mask as this had already been done on the prior layer. Then this was flattened and sharpened by using a LAB Mode Sharpening technique and only running a 25% opacity on this new layer.
I was quite happy with the technique, all of which is lossless and can be constantly re-adjusted once saved as a .psd file.