ISO 100, OMD-EM1II and firmware 3.0?

Started 2 months ago | Questions thread
OP Architeuthis Regular Member • Posts: 159
Re: ISO 100 Compared to Overexposure

Cafe Racer wrote:

Richard Turton wrote:

Can the same results as ISO 100 be obtained by over exposing ISO 200 by one stop? The answer is no. The Signal/Noise Ratio of ISO 100 is almost a full stop better than ISO 200 overexposed by one stop. The available headroom is lower with ISO 100, but as long as clipping does not occur you will get less noise with ISO 100.

Have you tested the E-M1ii to see if an ISO 100 image has any additional brightness added?

I had some time at the weekend and made test shots. Noise filter off, noise reduction off, Auto WB, raw files.

First I exposed to the right (ETTR; center spot) at ISO200 and then made test shots at ISO100 and ISO64 at identical aperture/shutter settings. Clearly the raws were darker at lower ISO (according to DxO the rwas should all be all at the same ISO83) and the histograms at lower ISO show that there is plenty of room for brighter pixels left. Unfortunately, I do not have the means here to look at the histgram spacing as bobn2 suggests. I corrected exposure in LR (+1 eV for ISO100, +1.6eV for ISO64), exported JPEGs. They are now of very similar brightness and I cannot detect any differences in S/N ratio in the shadows. In case there are differences, they must be very subtile:


Extended ISO100

Extended ISO64

I conclude that (by a strange mechanism that I do not understand) the low extended ISO settings provide similar S/N ratio as base ISO200, but allow to collect more light (just as the differences in ISO values suggest). I will not hesitate in the future to use the low extensed ISOs, when light permits (unless someone convinces me about the opposite)...


P.S.: I also made a test series to find out where the "ISOless" range of the EM1II starts. I will, however, open a new thread, since this is a different aspect...

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