On the dynamic range of RAW...

Started Nov 30, 2004 | Discussions thread
OP Brian G. Veteran Member • Posts: 6,531
Well, not exactly...

Hi Anders,

echelon2004 wrote:

Please note that all the pics we see are 8bit jpeg's.
It is possible to get the same result's by spot meter the brightest
and darkest points and then calculate the exposure from both these
points.

Well, you won't get exactly the same results doing that. I am a huge fan of spotmetering, but when you meter your lightest and darkest points and get an exposure based on those, you are getting an average exposure. If you are shooting in jpg, you will still lose the darkest blacks and lightest whites as your images is converted to jpg in-camera. Even Olympus' multi-spot metering is just a weighted average calculation based on the areas you've metered for it. You will still have more dynamic range shooting the scene in RAW. In the example I posted above, that image was processed within a range of 8EV. No jpg will give you that- the info just isn't there in an 8-bit file. Remember- a 12-bit RAW files contains 4,096 discrete tonal levels. An 8-bit jpg contains 256. Tonalities are always lost during the conversion to jpg. If your exposure was good to begin with, and within the limts of the camera's sensor, then it doesn't matter too much- 8-bit will be fine. But if you need to really start adjusting, jpgs simply cannot compete.

I found a good article for anyone who would like more info:
http://www.normankoren.com/digital_tonality.html

This is a great site, incidentally, and there is much useful info there.

If reducing the contrast in cam the result should be about the
same, naturally without the controll and predictability=)

If shooting in jpg, I would defintely reduce contrast to capture as much detail as you can without blowing highlights. In fact, when I shoot jpgs, I always have contrast turned down as far as it will go (-5 on my 8080). But even here, you'd be better off shooting in RAW instead as far as dynamic range goes.

I allways shoot raw though so don't really know why I'm making this
post

Nice pics!

Well thank you.

Kind Regards,
Brian

Anders

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