Relationship between Sensor Size and diffraction

Started Jul 22, 2013 | Discussions thread
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quadrox Senior Member • Posts: 1,132
Relationship between Sensor Size and diffraction

I have never quite understood how larger formats are supposed to allow for higher resolution, but I have now realized a good way to phrase my question so I might get good answers.

As far as I understand it, the following points are generally accepted to be true when comparing sensors with identical resolution:

  1. All else being equal, smaller sensors will suffer more from difraction when using a given f-stop due to smaller pixels.
  2. All else being equal, smaller sensors have more DOF at a given f-stop.

My main question is now, will the two effects above cancel out for equivalent photos? That is:

Will equivalent photos taken at the same resolution, with the same FOV and DOF have different amounts of diffraction?

My intuition says that they will have the same amount of diffraction. If that is correct, I see one alternative aspect where larger formats may yield higher resolution: Lens sharpness.

Once more, it is my understanding that:

  1. Lenses for smaller sensors are easier to make sharper than lenses for larger sensors...
  2. ... But because larger sensors (having same resolution) will have larger pixels, this effect is again reduced

So therefore my second question is:

Will Lenses for larger formats generally be sharper relative to sensors size than lenses for smaller sensors?

My intuition says no, there won't be much of a difference. And if my intuition is correct, then I am really wondering where the supposed superior resolution for larger formats is coming from. I appreciate any answers that make this clear to me!

 quadrox's gear list:quadrox's gear list
Canon EOS 5D Mark II Canon EOS 7D Canon EF 85mm f/1.8 USM Canon EF-S 17-55mm f/2.8 IS USM Canon EF 55-200mm f/4.5-5.6 II USM +2 more
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