Exposure basics, lesson two point one (& ISO)

Started Mar 19, 2013 | Discussions thread
Steen Bay
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Re: Correction: G3 vs EM5 - Estimates of Ratios of Light Exposure
In reply to Jack Hogan, Mar 21, 2013
I wonder what Anders thinks about that. Will be interesting to hear from him.

I am waiting with garlic breath

Also, I calculated the difference in QE at these ISOs to be less than 1/6 of a stop, which correlates relatively well with Sensorgen's which you used. On the other hand, I believe mine is more precise because I assume a blackbody radiator at 5000k as the light source, while Bob assumes a green laser

How did you calculate the QE then ? Seems like it would be a factor in the ADU/Photon gain ? The SNR varies by the square-root of QE multiplied together with the number of Photons. How would one be able to separate-out the QE from the number of Photons ? Your stated 11% (below) is quite a bit less than the 17.78% difference that Bob's Senorgen data indicates. How do you relate it to a black-body radiator (as opposed to a monochromatic Green wavelength) ?

Perhaps it would be worth a separate thread in the Open Forum. Here is a sneak preview with the D5200 as the subject

Jack

PS WTH is going on with the editor?

At high ISOs (like 2-3 stops above base ISO) the PRNU noise doesn't seem to affect the SNR near full saturation, and according to DxO's SNR 18% graphs the E-M5 has about 1 dB better SNR than the G3. Doesn't that indicate a a bigger difference in QE than 11%?

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