On the dynamic range of RAW...

Started Nov 30, 2004 | Discussions thread
Guy Parsons
Guy Parsons Forum Pro • Posts: 30,326
RAW noise

ecm wrote:

A specific question for Guy:
I tried to use RAW on my C-5060 to do some portraits, and I had a
lot of trouble with graininess, ie. very high noise levels. It was
like I was shooting at ISO 400 (or worse), but I'd set the ISO at
80 manually. Is this normal for RAW?

I haven't seen noise increase in RAW but then I've never tried slow shutter speeds with artificial light. I'll do some testing later to see if I have problems. The noise from the CCD is there in the RAW files, maybe it's the RAW conversion not working properly or not applying enough noise reduction in the edit program.

I kind of wonder whether the in-camera processing to produce the
SHQ JPEG's has a noise reduction filter - I did a bunch of SHQ test
shots while getting the exposure right, and they looked a lot
better, noise-wise.

All cameras seem to have noise reduction built in, but Olympus err on the under reduction side so end up with more noise but less of the awful plastic look of many of the others.

The light was not ideal, I was using a 300W Halogen lamp through a
white sheet (as a homemade soft-box) and a couple of 50W halogen
lamps for lighting the background; I also used an external non-TTL
flash bounced off of the white ceiling. My exposure time turned out
to be about 1/15s with f2.8, and 1/4-1/10s with f5.6. Do you think
that the long exposure time was the issue? I could relatively
cheaply add a couple more Halogen lights - it'd bring up the light
levels considerably.

Longer exposures do allow for more random electron noise to happen, but edit program noise reduction should be able to handle it.

Another issue was trouble with trying to set the white balance -
even when the flash was turned off, it would fire when I tried to
use a white card to set it manually; so every picture had a red hue
(to make up for the blue that the flash light produces, I assume).
Do you know whether there's a way to turn this off? I ended up
covering the flash with my fingers! Very inelegant.....

I thought RAW didn't have white balance, that's done later at RAW conversion time. Or are we talking about the JPEG here? I need to read the book but there has to be a way to manually set a likely white balance based on type of lighting. Anyway, small white balance errors can easily be sorted out in the edit program. I use Auto WB all the time and have very few problems. Your mixed lighting may cause problems, you need to have a filter over the flash to make it the same colour temperature as the halogen lights, or you really should try halogen lamps only.

Hope something there may help....

Regards........... Guy (gotta log off now) Parsons

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