Diffraction Limit Discussion Continuation

Started Feb 21, 2014 | Discussions thread
Steen Bay Veteran Member • Posts: 6,978
Cambridge in Colour

Steen Bay wrote:

Anders W wrote:

Jonny Boyd wrote:

I said that at low resolutions it's more of a plateau that a peak, so you effectively get the same resolution at smaller apertures.

No you didn't say that. You said the peak would occur at different apertures depending on sensor resolution (just as Cambridge in Colour). Do you want me to look up the specific posts for you?

Don't think Cambridge in Colour says that. As I read it he's talking about the point at which diffraction will start to become clearly visible at 100% view (with a good lens).

"Most will find that the f-stop given in the "diffraction limits extinction resolution" field tends to correlate well with the f-stop values where one first starts to see fine detail being softened. All other pages of this website therefore use this as the criterion for determining the diffraction-limited aperture."


The calculator says f/7.3 for a 16mp mFT camera and f/4.9 for a 36mp mFT camera. Sounds guite reasonable to me, as a (rather gross) rule of thumb.

P.S. - Maybe I should also have quoted his conclusion :

"Thus far, you're probably thinking, "diffraction more easily limits resolution as the number of camera megapixels increases, so more megapixels must be bad, right?" No — at least not as far as diffraction is concerned. Having more megapixels just provides more flexibility. Whenever your subject matter doesn't require a high f-stop, you have the ability to make a larger print, or to crop the image more aggressively. Alternatively, a 20MP camera that requires an f-stop beyond its diffraction limit could always downsize its image to produce the equivalent from a 10MP camera that uses the same f-stop (but isn't yet diffraction limited).

Regardless, the onset of diffraction is gradual, and its limiting f-stop shouldn't be treated as unsurpassable. Diffraction is just something to be aware of when choosing your exposure settings, similar to how one would balance other trade-offs such as noise (ISO) vs shutter speed. While calculations can be a helpful at-home guide, the best way to identify the optimal trade-off is to experiment — using your particular lens and subject."

Again, sounds quite reasonable to me. Don't quite understand what all the fuss is about.

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