# Exposure basics, lesson two point one (& ISO)

Started Mar 19, 2013 | Discussions thread
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 Re: Correction: G3 vs EM5 - Estimates of Ratios of Light Exposure In reply to Martin.au, Mar 21, 2013
G3 at ISO=1600 and EM5 at ISO=3200

(For the G3 relative to the EM5), the ratio of the Average RAW channel levels divided by the ratio of the DxOMark "Saturation ISO" ratings is 1.494 EV, but when receiving -0.322 EV less light (due to it's higher Shutter Speed), and transducing -0.236 EV less electrons due to it's lower QE. So, the G3/EM5 ratio of the amount of light received in that case seems to be around:

(For the G3 relative to the EM5), the ratio of the Average RAW channel levels divided by the ratio of the DxOMark "Saturation ISO" ratings is 1.494 EV, but when receiving 0.322 EV more light (due to it's lower Shutter Speed), and transducing -0.236 EV less electrons due to it's lower QE. So, the G3/EM5 ratio of the amount of light received in that case seems to be around:

+ 1.49 - 0.322 - 0.236 = + 0.9358 EV (91.289% more light)

Silly question, but could we also determine the accuracy of Jack's claim by taking two photos with with a G3 and an OM-D using the same settings, except for ISO.

Since the above analysis was performed on two RAW images recorded by each camera of the same scene with the ISO settings stated, the (perhaps seemingly obvious ?) answer would be "yes".

Processing them using the same method as DPR, and, well, looking at them. 1 stop is pretty obvious.

DPR provided unprocessed RAWs. In-camera JPG processing would muddy the measurement waters.

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