On the dynamic range of RAW...

Started Nov 30, 2004 | Discussions thread
OP Brian G. Veteran Member • Posts: 6,531
Re: thanks - question

Hello Unda,

Unda Covalava wrote:

Very informative, thanks for posting. I never realized RAW
contained so much info, especially in what appears to be blown out
areas.

Yes, it's surprising. With each extra bit you are doubling the amount of discrete recordable tonal levels. Consequently, you can think of a 12-bit RAW file as giving you 4 more EV worth of dynamic range over an 8-bit jpeg. (I'm not convinced that that analogy is 100% correct yet [I first heard it elsewhere]...but I suppose it is a useful way of thinking about the differences).

One thing though, I'm pretty sure RAW has undergone bayer
interpolation. Or at the very least, anything that you can view
that is RAW has had bayer interpolation done, otherwise you can't
view it. It just hasn't had any adjustments, and most cases no
sharpening either.

True about the viewing- if you can see it, it's been interpolated unless we are talking about viewing in-camera, where most likely you are looking at a jpeg thumbnail of a RAW image.

My understanding of the process is that it flows like this:

For JPEG-

Sensor Capture--> Readout Electronics, ISO Setting Applied, A/D Conversion--> Bayer Interpolation--> WB, Contrast, Saturation, Sharpness Settings Applied--> Jpeg Compression Applied--> Jpeg File Output

For RAW-

Sensor Capture--> Readout Elelctronics, ISO Setting Applied, A/D Conversion--> RAW File Output.

I could be wrong, but I'm pretty sure the above is correct. So my guess was that since the in-camera RAW files haven't undergone Bayer Interpolation they would be much smaller than high-bit level jpegs, even if those jpegs had some (not too much, we'd hope) lossy compression.

But again, I could be totally wrong. I just wanted to clarify my thinking.

Thank you for your post. This has been an informative thread.

Kind Regards,
--
Brian (el picador, Sir Brian)

Digital Image Gallery:
http://mywebpages.comcast.net/spiritmist/Brian_G_Digital_Image_Gallery/index.htm

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