Why 'more or less stopped using ISO'?

Started Feb 19, 2014 | Questions thread
bobn2 Forum Pro • Posts: 60,173
Re: Why 'more or less stopped using ISO'?

l_d_allan wrote:

In a recent thread where the OP was about base ISO
What determines a sensors Base ISO?

I was unclear about the following posts ...

bobn2 wrote:

Iliah Borg wrote:

Bob, even with film ISO rating is not very useful, it is just some approximate guideline. It is even less useful with digital. You know that...

I do know that, Iliah. Personally, I've more or less stopped using ISO.

I'm in the category of "not knowing that" ... about digital ISO being less than not very useful. Please clarify.

  • Is this specifically about "iso-less sensors" like many Sony and Nikon cameras?
  • So for such cameras ... just leave ISO at the camera's base ISO (typically 100)?
  • ...
  • Or does this also applies to Canon DSLR's (which I don't think can be described as iso-less)
  • Or because modern DSLR's have so little noise that use of Auto-ISO is appropriate?
  • So bobn2 and Iliah aren't concerned about what ISO is picked by Auto-ISO?

The whole concept of 'ISO' is based around a methodology which says 'choose a processing regime' and then 'choose an exposure to match'. The implication is that the purpose of controlling exposure is to control output image brightness. If you are one who controls the processing after capture, for instance by processing from raw, then you don't want to control exposure to conrol brightness, you need to control it in order to capture the maximum scene information, then you process to get the required brightness. Since ISO is all about mapping from exposure to output image brightness, it isn't much use when you want to maximise capture information - then you need to use other methodologies for exposure control, which have become loosely wrapped up as 'ETTR' or 'ISOless'.

In any case, what you're trying to do is use all of the sensor's capture range for whatever is the luminosity range of the subject.

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