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dslater
09-20-2007, 11:29 PM
Bit depth has nothing to do with dynamic range. It only has to do with the number of intermediate tones between extremes.

If a sensor can record detail over a 1000:1 brightness range (approx 10 stops), then increasing from 24 to 32 to 48 to 96 bits is not going to change the upper and lower limits of that range -- it will only change the number of intermediates.

To get a higher dynamic range, you need a physical sensor that is responsive over a greater range of light. Once you've accomplished that, then you'll need higher bit depth to accomodate all the data -- but it's the sensor and not the bit encoding that makes this possible.

The 32-bit files in HDR are necessary because each individual pixel holds the R/G/B information from 5, 8, 10, etc individual captures. So you need extra bit depth just to hold all that data. But it's not the bit depth per se that creates the higher dynamic range -- it's the content of that pixel information that does.

I am well aware of this - However, I think it is pretty obvious that digital sensor manufacturers wouldn't create a 32-bit chip unless the sensors had the dynamic range to take advantage of it.

DrPablo
09-21-2007, 09:55 AM
True. Though I think the dynamic range of current digital cameras is pretty much fine. All they need to do is make the shadows far less noisy and make the highlights end much less abruptly. DSLRs already have a much greater latitude than slide film, and they're comparable to a negative with standard development.

dslater
09-21-2007, 05:35 PM
True. Though I think the dynamic range of current digital cameras is pretty much fine. All they need to do is make the shadows far less noisy and make the highlights end much less abruptly. DSLRs already have a much greater latitude than slide film, and they're comparable to a negative with standard development.

Hmm - that's not what I understood. everything I've read indicates digital sensors have about the same dynamic range as slide film. In any case B&W film processed properly has a much wider dynamic range than digital sensors or color film. I'd like to see a digital sensor with at least as much range as B&W and preferably more. There are always difficult lighting situations that need more range to capture.

DrPablo
09-22-2007, 12:46 AM
Some guy on FredMiranda did a huge study in which people put their cameras on manual, and shot a series of pictures of a wall, adjusting exposure by 1/3 of a stop, and the dynamic range was determined to be the number of stops between the lowest and highest exposure setting where there was recognizable detail.

The average was something like 7 2/3 stops, and some people (mainly with full frame cameras) reported over 9 stops. I'm sure some of this DR is not necessarily useful DR, like the bottom 1 stop and the top ~ 1/2 stop. But still, that's a pretty good DR. Part of the problem is that there is no shoulder, though, so highlights end up being all weighted equally until they cut out. So the DR is qualitatively different than on film.

I haven't studied this formally, but I'd give Velvia maybe 4 useful stops in my experience, and Astia maybe 6 or 7. I definitely have to be more careful these days shooting slide film than I ever did when I predominantly shot digital. Then again I could shoot 800 pictures to make sure I hit the exposure on one of them, and I'm not doing that with 8x10 slide film.

bjorke
09-22-2007, 08:27 PM
I think "Photo Techniques" did a similar study (was it "Digital Photo Pro"?) that showed varying dyanamic range between a # of cameras. The best cameras did very well. What was interesting to me was that the camers with the widest DR were not known as the best cameras -- because, apparently, they also had a lot of variance (noise) in the extremes of their ranges. Cameras with low variance AND wide DR were, as you might expect, top-dollar items.

(At this point the little clown on a tricycle comes through reminding us all that film frames do not display these artifacts, and behave with great consistency across all acceptable ranges -- that is, they are still a match for the best commercial/consumer digi sensors)