A Recent Trip

[Dave Humphries]

Chris,

PITA = Pain In The

The last bit I'm sure you can guess
I obviously can't say or I'll rightly be sacked from here

Cheers,

[crisscross]

Perhaps PITB? (butt)

[Colin Southern]

I am getting really curious now. The cloud contrast is certainly increased/improved as is the rock colour in the lower shaded portion. But this is at the expense of loss of saturation everywhere else.

Hi Chris,

It can be a bit misleading. The original image may have looked like it had more saturation, but it was a bit of an illusion probably due to a colourcast. The basic technique in LAB colour to bring out subtle colour variations is to apply a curves layer and then steepen the "curves" on the A and B channels (not necessarily the same for each channel).

In this case I was able to get quite agressive with the A (Magenta/Green) channel, but far less so with the B channel -- so the sky was largely left unaffected. Steepening either channel will increase the saturation for those colour opponents across the entire image (assuming no masking), but a potential pitfall is that it will also greatly increase any colour cast that the image has. Although LAB is fantastic at removing colour casts by asymetric manipulation of the AB channels, it's easier to simply remove it in the RAW converter before one gets to that point, which is what I did (as it had quite a noticeable cast).

So steepening the A curve pretty much took care of accentuating the colour variation in the rock, but also had the side effect of making small areas of green vegetation over-saturated; fortunately there was very little of this (just a couple of plants) so a couple of clicks with the sponge tool set to desaturate fixed that. It would have been easy enough to ingrease the saturation of the "terrafirma" with a simple selection, but I think it would have turned the image into something it wasn't (getting in to personal interpretation territory).

Both the clouds and the foreground badly needed local contrast enhancement - I just used the burn tool (shadows and midtones) on the foreground, but the fastest way to do the clouds was simply a quick select on the whole sky and then a levels layer (bringing up the black clipping point) -- this of course also darkened the sky (a bit too much for that time of day), so a minor tweak of brightness on a HSB layer fixed that.

Sharpening was on L channel only - a bit tricky as there was a lot of high frequency component (made worse by the harsh lighting), so I has to use lower amounts on higher radiuses (this is the main reason I needed the original -- the posted shot was too low res) (also the reason I posted quite a high res shot back here -- if you want to see the full res version which is much better again, ask Jim to send you the sendthisfile link and you'll be able to download it for yourself (about 80MB off memory).

If your interested in LAB then the only book anyone will ever need is "The Canyon Conundrum" by Dan Margulis.

[joec]

Yes, Colin, nice description. Clears that up.

Joe