I finally 'get' equivalence

Started May 22, 2012 | Discussions thread
Mr Lumière
Junior MemberPosts: 47
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Re: I finally 'get' equivalence
In reply to Dorus, May 22, 2012

People have a really hard time understanding this concept and it seems you didn't graps it well either, please let me explain:

FF sensor capture more light in absolute terms, 4x more light.
FF sensors capture THE SAME AMOUNT OF LIGHT in rellative term.

In fact per pixel noise is directly rellated to pixel pitch not to sensor size, a 36mp FF sensor will have more noise per pixel than a 8mp m43 sensor of the same built for example.

The reason more light gets to the sensor is because the sensor is bigger, it doesn't get more light per pixel, at all.

You do not have more DR or less noise because of sensor size, you get that out of pixel pitch.

However if a FF sensor has 12mp and a m43 sensor has 12mp it is safe to assume that the FF sensor will have better dynamics, but only because the pixels will be bigger and let more light in.

In a more simple way, if you crop a FF picture by a factor of 4 do you get more noise? Less DR? No.

If a scene requires a FF sensor equiped camera to use an f2 aperture at ISO 400 it will also require a m43 sensor equipped camera to use an f2 aperture at ISO 400.

Noise and DR are the result of pixel pitch not sensor size, and to some extent processing, and that is as long as sensor built is identical.

Equivalence in term of distance from subject and DoF are affected by a 2x factor, a 25mm lens will require to be as far as a 50mm lens on a FF camera, an f2 aperture on m43 will give you the same DoF as an f4 aperture on FF.

This is all rather simple really.

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