Thursday, August 11, 2011

RAW Therapee As a JPG Editor Part1

It was the Raw in RAW Therapee that attracted me at first. Then, as I said in the last post, I wrote a tutorial for a flickr contact who underexposed her vacation photos. That sent  me deep into the archives to my P&S days when I could only shoot jpgs. Which brings me to this post, a look into the unique RAW Therapee features that other jpg editors, free or pricey, lack.


I shot this in 2007 at a summer tradition--the Madison Symphony pop concerts on the Capital Square. My son who had moved into an apartment off the square invited me to join him and some friends for a picnic and music.  Both the food and the company were excellent, but they had laid out their blankets away from the crowd.  So I couldn't see the orchestra which limited my photo opportunities.

But that changed. During the intermission as the sun was setting and the light had become golden this girl began to crawl on the railing in front of us. During my fresh look at the photos--after four years I forgotten I'd taken them--it was the staircase in the background that first caught my attention.  If I could brighten the girl slightly, or conversely darken her into a silhouette, plus make the staircase more golden I might have an image worth posting.

As expected the first slider on the exposure tab, exposure compensations, brightened the girl but killed the staircase. It moves the white point of a RAW file, the value RT set to 255, 255, 255 when it create a new jpg. With just a jpg saved in the archives that data disappeared 4 years ago the instant I press the shutter for the next photo. Not useful for this task.

For a darker silhouette version the black slider was more useful


By moving it up from 0 to 9600 I closed a gap in the histogram to darken the girl. Moving the Brightness slider up to 20 lightened the staircase but at the cost of the golden color I was looking for. Ok but not what I was after

To get the image I wanted I turned to the RT tone curves.



The first tone curve on the tab works with the RGB data. It lightened the girl nicely but eliminated the golden light on the staircase.  By pulling the curve up I changing how bright the Red, Green and Blue dots that make up the  girl pixels would be on yours and my monitor.

RGB tone curves introduce color shifts. Depending on what you are after this might or might not be a problem. For instance, if I had wanted to restore the original white color of the staircase, the color shift would have been an improvement.

RT's second tone curve at the bottom of the tab works with LAB data. It's a tone curve I've not seen in any other RAW convertor or jpg editor.

LAB stands for Luminosity, A and B channels where the L channel has all the brightness data, the A channel has all the red and green data and B the blue and yellow data.

Or if you aren't interested in the LAB color theory stuff--I have a thick book just on how and when to use the LAB mode-- the one thing to remember is that RT's second tone curve works only on the Luminosity channel. It doesn't touch the color information. So no color shifts ever.


With this conversion, besides brightening the girl with the tone curve and the brightness slider I added a bit more saturation to make the staircase stand out more against the different granite in the capitol walls.


The flickr posted version after I used RT's straightening tool to hide my habit of never getting the horizons, real or virtual, level.

As for the other tabs, Highlight Reconstruction is greyed out since it works only on RAW data during the demosicing operation. It does a great job too but it doesn't fit into this post.

Shadows and Highlights does work. If you want to use it conservatively as high end image editors such as Photoshop forces you to do, I'll refer you to Paul's excellent and readable manual. It now ships with your RT downloads and is also available in the documentation section on the RT website.

But if you are in a 'fun&crazy' mood try this.


Our girl once she found a spot to sit.


And after I ran the exposure comp up around 6 to drive almost everything into saturation and then played with the Shadow/Highlights tab to see what would happen. Try it on your own images. It's fun.

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