f-number equivalent between m43 and FF

Started Mar 25, 2014 | Discussions thread
bobn2
bobn2 Forum Pro • Posts: 53,155
Re: f-number equivalent between m43 and FF
1

D Cox wrote:

Great Bustard wrote:

How does a pixel know how big the sensor is ?

It doesn't. It's also not relevant, except inasmuch as the pixel count affects sensor efficiency. For example, if we had two sensors, one with 12 MP and the other with 24 MP with the same size and same QE, then if the read noise per pixel were the same for each sensor, the 24 MP sensor would be more noisy (although this would only be apparent in very low light).

Exactly. And it would be more noisy because the pixels are smaller.

Wrong. It would be more noisy because it had more pixels. So far as read noise is concerned, smaller pixels tend to be quieter, but not enough quieter in general to fully compensate for the increased number. So, for instance, compare the D800 and D610 which pixel for pixel perform almost identically, the D610 is marginally quieter in the shadows though in truth, the difference is small enough that it can be swamped by exposure management and processing differences. For instance, looking at DPR's new tool

The D800 looks the quietest in the shadows (and overall) - we know it ain't so, but there is enough tolerance in DPR's method to swamp the real differences over a 3:1 difference in pixel area.

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Bob

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