I didn't know what the 'Auto Lighting Optimizer' did so I tested it.

In the first found of tests I didn’t see that much difference with the fan. However on the ‘Strong’ setting I could see the text in the middle of the fan a little bit better. In the second round the strong setting again provided a noticeable difference in my face in contrast to my black jacket.

I didn’t see any noise issues at this lighting level, I mostly saw a difference in brightness. I will have to try testing this at night sometime.

I think I will leave it on ‘Standard’ for my photography and ‘disabled’ for my videos on the T2i.


  • Frankly I don’t see much of a difference so for that reason my own choice would be to either turn it off or put it in the low setting. It just makes sense to me not to have the camera’s CPU doing any unnecessary work.


  • Thanks for the info. I had this disabled on my camera since that is what I normally do if I’m not familiar with what a feature does. The printing on the fan is much more legible with the higher setting. Whether I’ll enable the optimizer will depend on conditions since the background does lose contrast.

  • It looks like a change in contrast (or a curve function) reading elswhere, the noise comes from the fact that (with ALO on) the camera actually underexposes then pushes up the gain (dynamically)in the image. This preserves whites or peak information and pulls up blacks or toe information, but by increasing gain all you do is reduce signal to noise. ie. pump noise in dark areas.

    Thats OK outside where there is lots of light and the camera is working in low noise mode, but not so great indoors where the camera must pull up gain anyway.

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