MFT Users: Do you miss the shallower depth-of-field of bigger sensor cameras?

Started 8 months ago | Discussions thread
Great Bustard
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Diffraction.
In reply to Dave Lively, 8 months ago

Dave Lively wrote:

nrwhitman wrote:

Fiisn't part of the gain with MFT the 2x multiplier so for a given FOV you use a lens of half the focal length and have the advantage of the better DOF? So in this sense sensor size would bring an advantage, or at least allow DOF without having to close lens down and risk diffraction?

Cameras with high pixel density sensors are more sensitive to diffraction. If a 16 MP FF camera starts to lose too much resolution due to diffraction at f16 a 16 MP m43 camera will start to lose too much resolution at f8. A 25mm lens at f8 will have the same DOF as a 50mm lens at f16.

If you look at the formulas or calculators for diffraction you will see that the amount of blur caused by diffraction depends only on the f stop, not the focal length. At f16 a pinpoint of light will be an Airy disk 21.3 um across regardless of the focal length. The size of this disk is proportional to the fstop so it will only be 10.7 um at f8. Since m43 has to pack the same amount of pixels into 1/4 the area they are going to be smaller. A 21.3 um circle that covers 1 FF pixel will cover 2 pixels of a m43 sensor with the same number of MP.

The fact of the matter is, however, that all else equal, more pixels resolve more detail, but that detail advantage will asymptotically vanish as the DOF deepens due to diffraction.

For example, the 75 / 1.8 on a 16 MP sensor will have up to 15% greater resolution than on a 12 MP sensor at its sharpest aperture. However, by f/22, it will resolve all but the same.

So when you say "Cameras with high pixel density sensors are more sensitive to diffraction", it makes it sound as though more pixels are a bad thing, in terms of resolution, when, in fact, it is the exact opposite, regardless of the aperture.

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