5Dii - Auto Lighting Optimiser

R

reheat module

Messages
2,681
Name
Paul
Edit My Images
No
Please help
Ive confused myself reading and re-reading the simplest of paragraphs in the instruction manual regarding using Auto Lighting Optimiser on the 5Dii.
It seems for JPEG I do nothing, but can use any of the 4 settings for RAW - but then it states that the settings can be adjusted in DPP?
In that case, why use 0,1,2,3 as a C Fn if RAW allows control in your workflow?
Also, does it achieve anything that a check of the histogram and exp comp couldn't do?
When would you more experienced guys & gals use it?
Many thanks
Paul
 
ALO is like having the camera run "Auto Levels" for you. It may make things better. It may make things worse. If you use it when shooting in JPEG the camera's decisions will be baked into the file. It has been known to be the cause of noise in files, particularly when the photographer screws up the exposure (underexposes) and ALO tries to fix the mistake.

If you enable it when shooting raw the raw data will be unaffected. However, the file will contain a field that indicates the setiing chosen. DPP will read this setting and apply it when you open the image. Of course, being raw, you are free to change the value of that setiing as you like, either enabling or disabling it or adjusting the strength. Raw processors other than DPP will ignore the field and carry on business as usual. The value of the field won't matter a scrap to them.

Even if you do shoot raw the ALO setting will be applied to the embedded JPEG preview image, from which the histogram is generated. This is great if you want little clue to how well you are exposing. If you'd rather have a meaningful histogram I strongly recommend you disable it.
 
My experience of ALO is that is does very little, even on the strongest setting with a 5DII it's very subtle. Which is a shame really for JPEG shooters - it needs to do a lot more to make a meaningful difference, if you like that sort of thing of course. Makes b****r all difference to the histogram too.

The other Canon image trick, Highlight Tone Priority does work however, even if the effect of that is not very dramatic either. It does hold a bit more detail in the highlights, at least half a stop maybe 2/3rds, and that is shown in the histogram which gets pulled back from the right hand side.

The control that affects the histogram most is the contrast setting in picture styles. If you're shooting Raw and pushing to expose to the right of the histogram, setting just that one control to -4 will give you a better idea of how much headroom you've got. By the same token, switching the HTP on also gets you just that little bit closer to knowing how far you can push it.
 
Actually ALO does seem to have far less impact than I realised. Certainly I have read several reports on the internet of problems with noise and it appeared that ALO was at least partly to blame. Still, personally I have absolutely no use for it and just leave it turned off, together with all the other in camera processing such as NR, LPIC and definitely HTP.
 
tdodd said:
Actually ALO does seem to have far less impact than I realised. Certainly I have read several reports on the internet of problems with noise and it appeared that ALO was at least partly to blame. Still, personally I have absolutely no use for it and just leave it turned off, together with all the other in camera processing such as NR, LPIC and definitely HTP.
Click to expand...

I thought you might say that ;)
 
You must log in or register to reply here.
Back
Top