How to see diffraction in photos

Started 4 months ago | Discussions thread
finnan haddie
finnan haddie Regular Member • Posts: 457
Re: How to see diffraction in photos

cba_melbourne wrote:

finnan haddie wrote:

cba_melbourne wrote:

...

But the effects of diffraction only become apparent in our picture, when the size of the airy disc exceeds the pixel size of our sensor. And that happens the sooner, the smaller the pixel size is.

On a 20 MPix MFT sensor that would mean around f/2.8.

Interesting, is that with the Bayer mask, or without as in a black and white sensor?

For both types of sensors. A Bayer mask just adds funny false colors at the edges.

Another way to explain is this. As long as the airy disc is smaller than the sensor pixel, the lens outresolves the sensor. Only when the airy disc (due to diffraction) becomes larger than the pixel size, can we begin to notice a loss of sharpness.

Not true. In particular with non-circular apertures you'll notice the effects of diffraction way earlier, e.g. sunstars.

Most modern lenses do have near circular apertures. But yes, some older repro lenses had indeed square shaped apertures. Beneficial for sharper edges when reproducing texts, or to create half-tone films (before the invention of contact screens in printing).

For $50 you can buy a used Schneider Componar enlarger lens with square aperture. It produces not round, but square bokeh, and 4-ray sunstars:

Or what about the 1964 Ricoh Rikenon lens with triangular aperture? Enjoy the video:

Yup.

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