Apologies for being so late to proceedings! I have been looking in on this thread throughout the day, but have only just managed to have a crack at the image (I'll be quicker responding on weekdays)...
It's interesting - when I downloaded the image I initially thought that the colour looked pretty good, and that it would just need a contrast and saturation boost, but taking a closer look I realised that there was more to do :)
Before opening it in CurveMeister I looked over it using the Photoshop Info palette, with the sample readouts set to Lab. I noticed:
- The sky was a little greener than I generally prefer, so I noted that I'd need to push that slightly towards Magenta.
- The grass was too red. It was positive in the A channel, rather than negative, and therefore needed to be pushed away from Magenta - towards Green.
- The water was too green in some places. In the lower left of the image (for example) the A channel was either equal to, or higher than the B channel, so I knew that I would want to address that as well.
Having checked for colour casts I checked whether there was enough separation in the L channel between the grass and the other features I needed to fix. The L value in the grass was between 20-30, and overlapped some areas of water that I wanted to alter. Because I wanted the grass to be greener, but the water to be less green, I felt that RGB and CMYK would both be bad choices for correcting the casts initially - so I chose to begin in Lab.
My intial Lab curves (attached) improved everthing except the grass, which still seemed too red. So I applied the Lab curves, and followed them up with CMYK (attached) to improve the grass. In CMYK I also curved the Black channel to improve the contrast more (I only set a highlight point in the first Lab curves, as nothing else seemed on the cards).
Having applied the CMYK curves, I returned one last time to CurveMeister to boost saturation in Lab. I steepened both the A and B channels - initially using the saturation slider, but having done this I decided to steepen the A channel further to boost the colour in the grass (this also helped the sky).
Returning to Photoshop, I applied Shadow/Highlights and sharpening (both conventional and Hiraloam).
I'm pleased with the improvements I've been able to make, but I'm sure that if I was more proficient it wouldn't have taken three separate applications of CurveMeister to get there. The aspect of curving that I have most trouble with - and am most hoping to improve - is the correction of colour casts, so I really enjoyed working on this image. I'm really excited about this course :)