ISO, DR and DxO benchmarking explained

Started Sep 26, 2012 | Discussions thread
perhort Regular Member • Posts: 133
Re: ISO, DR and DxO benchmarking explained

gollywop wrote:

bobn2 wrote:

gollywop wrote:

christosthegreek wrote:

Like I said, do you all set your camera to base ISO and under expose your shots then fix them in PP? I guess you don't and I don't know anyone who does!

I meant in my post above, to comment on this statement.

Yes, I do shoot like this as a matter of course. I adopt the strategy of attaining the highest exposure possible (a generalized notion of ETTR), where exposure is in bobn2's sense: f and SS, using the smallest f and SS consistent with my shooting constraints. I typically shoot A mode and set f in line with my desired DOF. I then adjust EC to maximize exposure based on blinkies (using UniWB) and an acceptable degree of blown highlights -- usually none. If the resulting SS is too slow, I set an appropriate SS (I may have to go to M mode for this). This may result in a dark image, as in the example I posted above:

It seems to me that this scheme would be practicable only for shooters who do not take IQ (noise, DR et c) into consideration. Brightening here seems to be a free lunch. In your example you do not trade off depth of field with IQ. Exposure affects three qualities namely motion blur, DOF and IQ. Most shooters trade off all three of them and hence need a dedicated "IQ-scale" such as ISO. A metering mode that ensures that no highlights are blown would be a good thing, though.

Similar to what I do. I just wish camera manufacturers would introduce a UI that would make it a bit more simple. I speculated on this a bit back, and produced this mockup:

Essentially you use it in manual mode, the meter has two scales, each measuring in a unit which is essentially milli-lumen-seconds (as I remember) so is sensor size independent. It is a matrix meter, the top line meters highlights, the bottom average illumination. The carets are user settable to their own quality threshold. All you do is adjust f-number and shutter as you want, if either bar is the wrong side of your quality threshold, choose which compromise to make. One can imagine a set of auto modes that would do that for you, a bit more sensibly than the current ones - all based on the idea that you adjust exposure to adjust image brightness - do. Of course, with an EVF like the E-M5, the highlight bar could probably be better done with blinkies.

Again, a metering mode/scale that ensures non-blown highlights would be a good thing. I don't follow how the second scale works. How does your illumination scale differ from an ISO-scale? It appears to me that your illumination scale is equivalent to an ISO-scale but with numbers normalized to stops, or am I wrong?

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