ISO 100, OMD-EM1II and firmware 3.0?

Started 2 months ago | Questions thread
Chris Noble
Chris Noble Veteran Member • Posts: 3,144
Basics of digital camera ISO

richarddd wrote:

katastrofa wrote:

bobn2 wrote:

Chris Noble wrote:

bobn2 wrote:

Chris Noble 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?

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...


Base is the lowest analog gain before A/D conversion. It's the lowest noise setting.

Extended (top and bottom of the range) is digital manipulation. No SNR improvement. And only useful for shooting JPEGs.

These definitions do not always work.

What kind of work are you referring to? They are definitions.

They don't work when it comes to sensibly delineating 'base' or 'extended

In any case, what you're calling 'base' is not the lowest noise setting. It's generally the highest noise setting so far as electronic noise goes.

Lowest gain = lowest noise introduced by the electronic processing.

Incorrect. It confirms my impression that you're working on the very common but completely nonsense accounts of what ISO is, what it works and what is the significance and effect of 'gain'.

So far as the shot noise goes, any increase in exposure will lower it, so the (so called 'extended') settings below will give less noise.

You are confusing noise due to the particle nature of light (shot noise), which the camera electronics can't do anything about, with the noise introduced by the camera electronics, which is what base ISO refers to.

I'm confusing nothing. I'm separating the two, which you failed to do, for the sake of clarity. With respect to the noise introduced by the camera electronics (or read noise) that reduces as ISO is increased, in general.

My photos look more noisy when I increase the ISO. Why?

Probably because you decrease exposure. That is, either you manually or the camera automatically increases shutter speed, increases f-number or both.

A lot of confusion in this conversation. Might be useful to start with the basics:

In a film camera, ISO refers to the sensitivity of the film. In a digital camera, the sensor sensitivity is fixed. The term ISO is used in a different way: the ISO setting controls an analog gain stage between the sensor output and the A/D converter. The higher the ISO setting, the higher the analog gain. The "base" setting is the lowest analog gain. The "native" settings are the various analog gain settings. The "extended" settings are extensions beyond the native settings that are obtained by digital scaling after the A/D converter. Because the extended-ISO scaling is digital, there is no benefit if you are shooting Raw as you can effect the same scaling in post-processing, with finer control.

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