Sunday, January 27, 2013

Tone Mapping JPGs---Or Why I'm Loving CIECAM02

At times we users fixate on the RAW part of RAWTherapee and fail to notice how great it is postprocessing JPGs. In fact I'd be willing to nominate RT, or should I say JT, as the best JPG editor on the Internet.

Example. I took this image last fall when Wife and I set out on a country ride to find a Halloween pumpkin for the front porch.  At a 'take your pick and please put the money in the cash box' roadside stand Wife walked about selecting the perfect pumpkin while I walked about snapping photos. Like this one of Indian corn.



The corn kernels are especially underexposed. I'd been shooting landscapes with the camera set to -0.33EV so not to blow out the skies and, as often happens, I forgot to change the setting . The camera also picked its exposure based on the bright husks. So how well will CIECAM02  tone mapping with JPGs?


Quite well as it turned out.

For the post proceed jpg I used pretty much the same workflow I described in my last post.
1-click the appropriate boxes to turn on the tools
2-click the highlight exposure warning icon. (white triangle on main tool bar)
3-use a single custom S curve to bring out the colors on the corn cob. When I went too far with the curve, the blown highlight on the individual corn kernels blackened. When I post processed a test jpg using that curve the rich colors washed out.
4-fine tune to taste using the Brighness, Colorfulnes and Contrast sliders

Are the results better or worse using the JPGs instead of NEFs?

 Wife walked in when I had a JPG version up on the screen next to a NEF version. She immediately picked the JPG version as the best. Since I'd used more Contrast on the JPG , I'd lean more towards a tie. With some images using a NEF would be better or even necessary. Recovering blown highlights, for instance, happens before the demosaicing step and won't work with a JPG. But with this image I could pixel peak with tight crops without seeing much difference.

So what are the advantages of using JPGs?

On the technical side speed and memory usage. Users with older 32 bits machines should find this quite useful.

And on the social side, there are mucho more JPGs out in the world than there are RAW files. Even on my machine. I have about five years of JPG only photography from before I owned a RAW enabled camera waiting to be sorted out and made more perfect for the digital version of the family album I've been promising to create.

No more excuses. Just don't tell Wife. Or even worse the Grandmas.

You can find this build of RT at-
http://www.visualbakery.com/RawTherapee/Downloads.aspx

Unfortunately as of January 27 there is no manual entry for CIECAM02. But it will appear shortly. The online manual is at-
https://docs.google.com/document/d/1DHLb_6xNQsEInxiuU8pz1-sWNinnj09bpBUA4_Vl8w8/edit

For Jacques's paper on CIECAM02-
http://jacques.desmis.perso.neuf.fr/RT/ciecamRT3.html


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