Nikon D850 - Ten Technical Questions

Started Oct 19, 2017 | Discussions thread
ChiArch New Member • Posts: 16
Re: Nikon D850 - Ten Technical Questions

Tony Beach wrote:

ChiArch wrote:

Tony Beach wrote:

praxxim wrote:

8. What is the diffraction limited aperture?

There is no such thing as "diffraction limited." I use the term diffraction impacted because that more accurately describes what happens as diffraction increasingly impacts acuity. It's not as if there is a brick wall limit to how much resolution you have or not as you stop down the lens.

There is a physical limit.

Really? Show it. Here's what I've seen:

Look at here

That's why it is called diffraction-limited.

Then if we add twice as many pixels per area then you would not see any more resolution because it has been limited by diffraction, but I'm not seeing that. Instead what happens is that as diffraction increases resolution drops off for a given lens and sensor, if the sensor and/or lens resolves more then using a reasonable aperture (most 135 format lenses only go to f/22) you will see more detail in spite of it being impacted by diffraction.

You need to compare the same sensor below and above diffraction-limit aperture (DLA) to see the resolution difference, not two different sensors at two different apertures.

Suppose there is a lens with ideal optical performance and a 1000px X 1000px sensor. When the F-number is smaller than DLA, the angular resolution recorded in the final image is limited by the pixel resolution of the sensor. That is the image on the focal plane is sharper than what the sensor can record.

When the F-number is larger than DLA, the angular resolution recorded in the final image is limited by diffraction. That is the image on the focal plane is soft (has a blurry edge), so the higher pixel resolution is unexploited. You still get a 1000x1000 file, but the image is soft.

Try a pinhole lens, then you will see.

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