Wednesday, August 3, 2011

RAW Therapee's Batch Processing to the Rescue

Autumn, a long time flickr contact, had a problem. During a vacation trip to Florida two years ago she went sailing and took a pile of photos with her Coolpic 550s P&S. Unfortunately her camera was accidentally setup with an EV of -1.7 and all her jpg pics came out ~4X underexposed.

Batch processing is not a new RT feature but until recently I hadn't realized how powerful and useful it could be.  I've taken my share of images with a setting wrong--white balance, exposure, etc--before I noticed and corrected it. So here is a mini tutorial using some of Autumn's photos on how I would use RT to hide these mistakes.

Start RT in its normal multi-tab mode and open the folder with the underexposed photos. Start by upping the exposure  +1.7 in one of the photo using the Exp Comp slider. Name and save your new profile.

Go into the file browser and control click on the other underexposed images.

Right click on the selected photos. This will bring up the new batch interface. Click on Profile Operations, Apply Profile, and in this case Autumn Underexposed, the name of profile I just saved.  Your copy of RT has a profile folder that holds all the default profiles that come with RT plus any you created and saved.

After a few seconds the thumbnails will brighten up. What have you done? Like Adobe Lightroom you haven't changed any of your photos. Instead you have created a pp3 file for the photos you selected which tells RT what changes you want to make.

What's next? If exposure correction was all you wanted to do, you could hit ctrl Q to put them into the Batch Queue. After selected what folder you want to save them to and the desired file format--jpg, 8 and 16 bit Tiff or PNG--you can hit start processing and let RT do its thing.

I preferred to fine tune the three photos I was working with.

The horizon was tilted, always happens with rocking boat photos, so I corrected that with the straighting tool  The overall photo was now exposed correctly but Autumn and her sister Jordan--wild hair--were still too dark. I used the LAB mode luminous channel on the Exposure tab to create a tone curve. I could have done this with the more common RGB mode but I think the LAB mode is cleaner since it doesn't introduce color shifts. Beside LAB mode editing on a RAW file is one of many features unique to RT. I also noticed that parts of the T-shirt were blown out so I use the Highlight Recovery slider to correct that problem.

After I finished editing the photos I put them into the batch queue.  There are two versions of the air plane image, each with different editing. Once I convert them I'll view them full size and decide which one I prefer. It's a great timesaving feature and a few days ago I converted the same photo 14 ways in one operation to check out the new profiles that showed up in the latest build of RT.

Although it wasn't necessary since I have 4GB of memory on this computer. I also closed everything but the batch queue and file browser.  If you look close, I forgot to circle it, you can see where the memory usage dropped in the Windows Task Master window.  RT can do many great things very well but that requires more RAM memory than the less useful free (and expensive commercial) editors. So if you have an older computer watch your memory usages.

How many great things can RT do very well? Here is the current list

If you click on Apply Profile (partial) you can pick what features you want to use from your saved profile. It is also a great overview of what RT can do

Finally I must thank Autumn for letting me use her photos in this tutorial.  You can find her flickr photostream at


  1. There are several ways of doing things in this particular case. One, maybe more direct solution, would be to select all identically underexposed image (you may use the filter tab of the directory browser for that), enter in the Exposure spin button (to avoid useless iteration since you know the value to use), and set it to 1.7. This will ADD 1.7 to all selected images, so if if one of them is already set to -1.0, your image will end up with a positive +0.7 exposure compensation. Weather this particular spin button value is added or replace the former one is set in the preference window.

  2. Hombre

    Thanks for the comment. Your method, detailed in the manual, works of course. But the one problem I saw when I tried it was that many
    unneeded operations in the file browser exposure tab were clicked by default.

    Because of that the thumbnail conversion times were several times longer than needed. With only a few images to convert the extra time didn't matter much, but if I were doing a big directory of image it would have been significant

  3. Can you do ~real~ batch processing in Linux (i.e. from the command line)? Whatever commands I enter just launch the GUI. What good is that?

  4. Since I don't use Linux I have no idea how the Linux builds work. Or don't work. You might want to ask in the RT forum.

  5. The answer as always is in the man page: man rawtherapee will show you the options with which you can run rawtherapee from command line.

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