RX10 Strange Low Iso Behavior

Started Feb 11, 2014 | Discussions thread
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breivogel Senior Member • Posts: 2,184
RX10 Strange Low Iso Behavior

I have been looking at RX10 raw files using RawDigger and a gray scale target. It is interesting to note, that (given a constant exposure value)  ISO 80 and 125 generate the same raw levels (aka "counts") and 100 and 160 give the same (higher) raw levels. This is somewhat consistent with what I have heard that the "Native" ISO of that sensor is 125.

Here is the data for the green channel on a middle gray sample.

F2.8 @ 1/3sec  all iso's

ISO =      80    100    125     160    200

Count = 4935  6033  4972  6028  7400

This means that there is less highlight headroom at ISO 80 and 100.

Though this makes sense in general, what is very odd is that ISO 100 produces higher levels than 125. It almost looks like a design flaw.

From an operational standpoint, there  seems no good reason to ever use ISO 100.  If you choose Iso 80 and expose as per  camera metering, you essentially get a +2/3 ev extra exposure (vs at 125)  which can be OK and would give lower noise level, as long as there are no highlight clipping issues. It would seem to me that you would get exactly the same result shooting at ISO 125 and adding +2/3 ev on the compensation dial.

 breivogel's gear list:breivogel's gear list
Panasonic Lumix DMC-LX7 Sony Cyber-shot DSC-RX10 Sony RX100 III Olympus TG-5 Nikon D300 +17 more
Sony Cyber-shot DSC-RX10
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