ISO 100, OMD-EM1II and firmware 3.0?

Started 2 months ago | Questions thread
bobn2 Forum Pro • Posts: 61,766
Re: ISO 100 Compared to Overexposure

Architeuthis wrote:

Cafe Racer wrote:


Thanks for that. Perhaps I should also open a new thread as what I'm trying to ascertain is not S/N ratio as base 200.

Hi Cafe Racer,

I am not sure whether I understand your question. But as I wrote above, no additional btightness is added to the histograms of the raw files - they look more or less as would be expected (-1eV (ISO100) and -1.6eV (ISO64)).

You're looking at the wrong quantity, both of you. What the histogram is measuring is exposure, though in camera and setting dependent units. The exposure will be the same, since the exposure settings (aperture, shutter) are the same and, presumably, the third exposure parameter, scene luminance (the light coming from the scene) is also the same. Therefore there is no way that it can be different. The setting-dependent units get scaled down by a factor of two each stop lower ISO that is set.

Here are screenshots of the histograms of the unprocessed exposures

'Unprocessed exposure' doesn't mean anything. 'Exposure' is sufficient, and is what is being shown. Processing a exposure delivers a lightness, not a different exposure.

that are shown above:


I'm not trying to be critical or pedantic here. Using the correct terms makes it much easier to conceptualise all this. Especially, confusing what 'exposure' is makes it really, really hard to work out what's going on.

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263, look deader.

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