Exposure basics, lesson two point one (& ISO)

Started Mar 19, 2013 | Discussions thread
bobn2
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Re: Exposure basics, lesson two point one (& ISO)
In reply to Anders W, Mar 20, 2013

How would it be (assuming that the sensor is linear, and that the entire Full Well Capacity is effectively utilized) that losing 0.2 stops of DR (by switching from ISO=200 to ISO=400) is better. What matters is the ratio of the Full Well Capacity divided by the Read Noise. Make sense ?

If exposure is kept constant and you are one EV short of the ETTR criterion at ISO 200, you don't lose 0.2 stops by going to ISO 400. Instead, you gain 0.8 stops. The full DR at ISO 200 is only realized if the sensor is saturated. Such is not the case in the scenario (originally outlined by Hogan) that I am talking about.

Just to add to this. The DR that is important in practice is the ratio of the read noise to the maximum signal that you use, not the maximum signal that you could have used, if you'd pushed exposure right up to the FWC.

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Bob

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