Why 'more or less stopped using ISO'?

Started Feb 19, 2014 | Questions thread
Luke Kaven Veteran Member • Posts: 5,705
Re: Why 'more or less stopped using ISO'?

l_d_allan wrote:

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 Sony Exmor family of sensors (used in, for example, the D3x/D800/D7000, Sony cams, Pentax K-5), by doing all processing on the sensor, much of it right around the photosite, reduces read noise such that read noise is near-optimal at base ISO.  Near optimal.

Among these, in the D800, there is apparently a slight measured noise advantage to using analog gain up to about ISO 1200.  But it is not a big advantage, and you could shoot at ISO 100 all day and all night if you choose.  Everywhere from ISO 1600 and up is done strictly using digital multiplication and no analog gain, and potential highlight bits are thrown away needlessly.  If you stay at ISO 1600, you can always defer on the decision to use gain for ... years if you wish.

The Canon cameras (at least the ones I know) are similar to the D3/D700, D3s.  These sensors route low-level sensor signals to outboard chips for amplification and A-to-D.  They are noise limited at low ISO settings.  I would use full-stop ISO settings in-camera for everything up to ISO 1600.  But everywhere from ISO 1600 and up, these cameras are basically linear, and you can top out your auto-ISO settings at ISO 1600 with some confidence.

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