DxOMark's measured ISOs vs. manufacturer ISOs

Started Mar 13, 2013 | Discussions thread
Jack Hogan Veteran Member • Posts: 6,982
Re: DxOMark's measured ISOs vs. manufacturer ISOs

Mjankor wrote:

Jack Hogan wrote:

Mjankor wrote:

For approximately equal output image brightness the numbers would be

Buzzzz! Reread previous posts. Exposure is only loosely tied to brightness.

Personally I'd have thought the best way to check IQ of a camera against other cameras if you were concerned about ISO would be to shoot the same scene with both cameras with the same shutter speed, ISO and aperture and have a look at the resulting photos. Maybe I'm a bit old school that way.

Nobody's stopping you from doing that, in fact you can check DPR's 'comparometer' as per my previous post. Too bad that if one manufacturer calls ISO 400 what another calls ISO 1600 you'd be unknowingly coming to the completely wrong conclusion... alas, for some ignorance is bliss


Well, I'm trying to get you to explain a way we can test this out, or something we should look for in testing between cameras, but you're not being very specific with testing ideas.

What do you mean?  When I suggested settings you said not to change anything

DXO's ISO doesn't relate to metering, or to the final image brightness, so what is the point.

It relates to Exposure.  That's a mother of a point for photographers.

Could you please explain the effects of this "Too bad that if one manufacturer calls ISO 400 what another calls ISO 1600" with regard to shutter speed, and ISO to achieve a final photo, and the noise level of that photo.

Exposure is only determined by shutter speed and f/number, all other things being equal.  It represents an actual number of photons hitting the sensor.  Double the Exposure, double the number of photons hitting it.  The number of photons hitting a sensor is a major determinant of IQ.  The larger the number the better the IQ.

ISO by itself has nothing to do with Exposure in a DSC.  If you double the ISO while keeping ss and f/n constant the number of photons hitting the sensor remains the same (remember what I said about IQ).  What changes are the output brightness values.  Now read this , something that Gordon alluded to earlier in this thread.

Happy to answer any further questions tomorrrow.



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