Exposure basics, lesson two

Started Mar 16, 2013 | Discussions thread
bobn2 Forum Pro • Posts: 61,125
Re: Connections

texinwien wrote:

bobn2 wrote:

texinwien wrote:

bobn2 wrote:

But under REI it is quite possible for different manufacturers cameras to select different exposures for the same scene and same ISO. Then the larger exposure will win. Unless of course your exposure is constrained by motion blur and DOF, in which case both cameras will have to set the same exposure (if the same format) and the one that wins might be very different.

Or unless, of course, the larger exposure leads to blown highlights.

Apart from panasonic, most manufacturers leave oodles of highlight headroom at their standard meter calibrations. That's why the DXOmark 'measured ISO' (which is actually sensor saturation point expressed as an ISI rating) is typically much lower than the nominal ISO.

I'm mostly familiar with the E-M5, which is certainly to be an outlier in regards to how much highlight headroom it offers.

Interesting. Some posters think that the discrepancy between the E-M5 Camera ISO Settings and the DxO "Measured ISO" or saturation-based sensitivity measures would somehow allow Olympus to make it appear as though the E-M5 has better noise performance at any given camera ISO Setting than it actually has at that setting.

I think that's bunk. But it's a bit of an aside, anyway.

I think it's bunk also, at least if you take just that factor. However, one wonders why olympus has left so much headroom, instead of putting in a lower ISO setting that many would have appreciated. As I suggested, one good stratagem to make low light performance of a camera appear better than it really is is to make the multi-pattern metering recognise low light situations and dial in more exposure. If one were doing that, it would pay to have a bit of extra headroom.

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