Exposure basics, lesson two point one (& ISO)

Started Mar 19, 2013 | Discussions thread
Martin.au Forum Pro • Posts: 13,246
Re: Exposure basics, lesson two point one (& ISO)

Jack Hogan wrote:

Mjankor wrote: Hey Jack, is the SOS measurement from the ISO standard an arbitrary value?

Yes, but don't take my word for it, check it out yourself. Meter off of a gray card in a few different modes, and see if middle gray comes out to 118 in sRGB. Does it ever?

Can you please explain how they can be arbitrary, with respect to the ISO standard?

Can you also please tell us what DPR are doing, when they do their ISO tests to the 12232 standard?

"If you want to compare ISOs between cameras from our reviews, look at the ISO test section (on the Noise and Noise Reduction page). This is where controlled test results are reported, essentially using the SOS method of ISO 12232:2006. The rest of the testing is based on knowing this SOS ISO calibration, as all test scenes have specific grey patches that are white-balanced and exposed as closely to L=50 as possible (i.e. within 1/6 stop)." - Andy Westlake

And, finally, can you please tell us how every camera I've looked at is consistent in this test? Why do all the cameras agree, if it's an arbitrary standard (oxymoron, I know)?

I assume this is an experiment you've done. Please tell us your results and methodology.

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