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Base ISO for Sony A7
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Author:  Jens Peermann [ Sun Sep 28, 2014 8:50 am ]
Post subject:  Base ISO for Sony A7

Desperate to know the base ISO for the A7, I so far found everything between 50 and 200 at various forums and blogs. A DXO DR chart I saw peaks somewhere between the 50 and 100 marks (meaning it's 64 or 80), but that chart refers to measured ISO which may not be the same as the ISO selected on camera.

I hope someone can de-puzzle me. Thanks

Author:  Mike in O [ Sun Sep 28, 2014 9:00 am ]
Post subject: 

100 iso

Author:  Royce Howland [ Sun Sep 28, 2014 9:09 am ]
Post subject: 

If you're after the "base ISO" from a pragmatic standpoint, i.e. the ISO at which signal-to-noise ratio, dynamic range, etc. are maximized -- then the DXO data gives the answer. It's ISO 50, which is the camera setting that's measured somewhere around 80 in the DXO charts. You can see camera ISO vs. measured ISO on the first chart, "ISO Sensitivity".

Actual base ISO may be something different, I suppose.

Author:  signgrap [ Sun Sep 28, 2014 9:47 am ]
Post subject:  Re: Base ISO for Sony A7

OK I have the same question for the Sony a7R:
What is the base ISO with base meaning the best signal-to-noise ratio, dynamic range etc.?

Author:  Jens Peermann [ Sun Sep 28, 2014 4:22 pm ]
Post subject:  Re:

Royce Howland wrote:
If you're after the "base ISO" from a pragmatic standpoint, i.e. the ISO at which signal-to-noise ratio, dynamic range, etc. are maximized -- then the DXO data gives the answer. It's ISO 50, which is the camera setting that's measured somewhere around 80 in the DXO charts. You can see camera ISO vs. measured ISO on the first chart, "ISO Sensitivity".

Actual base ISO may be something different, I suppose.

Thanks Royce. Looks like ISO 50 is the same as 100, only that it gets overexposed by one stop and that's where the extra range comes from.
Image


Dick, It's pretty much identical for all three of the A7 family:

Image



Correction: I planted the wrong chart. Here is the Dynamic Range comparison:

Image

Author:  signgrap [ Sun Sep 28, 2014 7:04 pm ]
Post subject: 

If I read the above chart correctly it looks like ISO 80 may have the most DR.
Is that an accurate interpretation for the a7R?

Author:  Jens Peermann [ Sun Sep 28, 2014 7:22 pm ]
Post subject:  Re:

signgrap wrote:
If I read the above chart correctly it looks like ISO 80 may have the most DR.
Is that an accurate interpretation for the a7R?

If I read Royce's answer correctly, DXO measured 80 when it was set to 50. So for maximum dynamic range and best signal/noise the camera should be set to 50.
That's at least what I am going to do from here on, until I find another setting to be better.

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