ISO 100, OMD-EM1II and firmware 3.0?

Started 2 months ago | Questions thread
Sergey_Green
Sergey_Green Forum Pro • Posts: 11,971
Re: ISO 100, OMD-EM1II and firmware 3.0?
1

bobn2 wrote:

Architeuthis wrote:

I have installed firmware 3.0 on my OMD-EM1II.

I wonder, whether the new ISO 100 brings better dynamic range, less noise and better colors compared to the base ISO 200, when used for raw files?

As John suggests in his reply, the advantage of a lower ISO is that you get (by definition) a larger exposure, which means a larger signal to noise ratio. That should give you a better actual dynamic range, simply because the largest 'signal' you're actually capturing is larger by a factor of two, This doesn't show up in 'dynamic range' charts, since they are based on the maximum signal you could capture, which you won't get if you expose according to the ISO setting, which is what most people do. Bill Claff's charts, to which John referred, have a peculiarity in that the ISO range is nominal ISO (i.e. the number your camera will tell you, rather than the ISO given by the exposure used) so don't really tell you much about what you'll get if you let exposure follow the meter.

I find it almost amusing seeing people posting link[s] to Bill's site while talking about something completely different than what this site shows.

As for raw files, raw files are no different from JPEGs, apart from there is likely more NR and other signal processing going in for raw files, except that for raw files, you have control over processing, so you don't need to follow the meter (for instance, you could 'expose to the right'). In that respect, the new ISO 100 has no advantage over the old 200.

Already in earlier firmware versions ISO 64 was available, but as far as I understand it, this does not improve DR, noise or color, but is useful only when too much light is present, to maintain wide aperture and increase exposure time...

I think your understanding a a bit awry. Nothing is different about the old ISO 64 except that the meter is calibrated for a larger exposure, and the in-camera processing is set up to render that larger exposure 'correctly'. This you get the advantage of larger exposure, as John suggested, which means less noise, more actual DR, if you expose according to the meter, and hence better colours. The risk is that you have less highlight headroom, and 64 encroaches into the JPEG standard headroom, so you can clip bright highlights. No problem if the scene is flat. Whether or not the 'better' you get is noticeable in general use is a completely different matter.

I think what he means is that native ISO is not the same as the extended ISO. In other words added through software update option will only allow for slower shutter speeds, but not necessarily better rendered images. If I read it correctly.

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- sergey

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