I was “playing” around, and decided to try the Auto Lighting Optimizer on my Canon 7D. Guess what? Nothing!
Was it a problem with the camera or a problem with the operator? It turned out that the problem was that I didn’t RTFM (Read The “Fucking” Manual or in a more polite way: Read The Fine Manual), meaning that the the problem was with the operator.
On page 75 of the manual, Canon mentions that the Auto Lighting Optimizer works only with JPEGs. The Auto Lighting Optimizer doesn’t do anything in RAW. In RAW, the Auto Lighting Optimizer only adds a flag that the processing software must interpret and process accordingly.
I use Lightroom, and Lightroom doesn’t do anything with the Auto Lighting Optimizer. At least I haven’t noticed any change. I have a friend that uses DPP, he can see a difference in the RAW processing.
What does The Auto Lighting Optimizer do for the JPEGs? It makes the photo slightly lighter by increasing:
- The brightness
- The contrast
- The noise in the shadows1
- If you have the Auto Lighting Optimizer enabled and try to under expose with the exposure compensation or with the flash exposure compensation, the under exposure will be ignored.
- Do not confuse the Auto Lighting Optimizer with the opposite, the Highlight Tone Priority, where the dynamic range is expanded (slightly) between the standard 18% grey and the highlights and the ISO range is reduced to 200 - 6400.
- You cannot have both the Highlight Tone Priority and the Auto Lighting Optimizer active. If the Highlight Tone Priority is selected, then Auto Lighting Optimizer is automatically disabled.
The increased noise is just a side effect of changing the curve control. I have tried it on a couple of JPEGs and it’s not as bad as it sounds. ↩