f-number equivalent between m43 and FF

Started Mar 25, 2014 | Discussions thread
dwalby Veteran Member • Posts: 5,556
Re: f-number equivalent between m43 and FF

bobn2 wrote:

dwalby wrote:

bobn2 wrote:

dwalby wrote:

Allan Olesen wrote:

D Cox wrote:

The total area of the sensor is irrelevant. If you put the same lens on various sizes of sensor, the noise level in the part of the image that they all record will be identical. (Assuming they are the same generation of technology.)

Let us compare the Nikon D800 (FF, 36MP) and the Nikon D7000 (APS-C, 16MP).

Same pixel size. Same Sony sensor technology. Same noise per pixel if you expose equally (same f-stop, shutter speed and scene light).

But not same magnification of the final output.

If you take the same photo with these two cameras and enlarge to the same output size, each pixel from the D7000 will be magnified 1.5x more in each direction. Consequently, the final output will appear more noisy.

And you can't really say I am wrong about that because I am actually just repeating your own claims from another post in this thread: The same pixel will look more noisy the more you magnify it.

So yes, it is all about sensor area.

I agree its all about sensor area, but I'm not sure I agree with your example.

In the case of two sensors of different size, but with the same size pixel, you have the same SNR for each pixel, we all agree on that.

Where I don't necessarily agree with you is that the simple act of printing the pixel larger or smaller will have any effect on its SNR.

A pixel has no SNR (in the context of a single photo)

a pixel has a signal level, as measured by the A/D converter, and an uncertainty due to noise.

Wrong. A pixel has a signal level as measured by the A/D converter. That is all, it gives a single value.

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OK, let me reword my statement a bit.  A pixel contains an analog signal value prior to A/D conversion.  Every analog signal has some sort of noise associated with it, and the A/D conversion itself introduces read noise.   So each pixel, when sampled, has a signal level, and some uncertainty due to the noise.

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