DLA is Nonsense! It should be deleted from the reviews.

[Daniel Browning]

Daniel better chime in here before this thread gets out of hand...or perhaps it is already too late.

After your excellent post, I don't think there's anything I could possibly add to the discussion. Of course, that's never stopped me before. []

DLA is Nonsense! It should be deleted from the reviews.

I respectfully disagree. It is not nonsense, and I like having it on the reviews. It tells me what f-numbers are capable of the highest sharpness (depending on the lens, of course) as well as the point of diminishing returns (in the context of a multi-camera comparison).

there is no limit from the pixel size and density.

Yes, there is. Every time I try to set my 24mm L II to f/32, a deep voice booms "thou shalt not stop down!" and a horde of crows materialize out of nowhere, pecking at me until I set it back to f/1.4. [] While there's nothing to physically restrain the photographer from using any particular f-number that they are capable of (and I don't mean to imply that you said there was), the sharpness of the resulting photo does have a limit, as well as a range of f-numbers over which the sharpness will be limited.

This theory assumes the image is a perfect dot and nothing else, and compares its airy disk with pixel size. If the airy disk is larger then pixel size, then the diffraction is visible.

As wickerprints said, it also applies to continuous surfaces.

There’s no such thing called perfectly pixel sharp images.

I think there is. The most extreme definition of "perfectly pixel sharp" that I can think of would be 95% MTF at Nyquist with no sharpening, and that can be achieved with sensors that are designed improperly (without OLPF) at low spatial frequencies. But I'm sure Bryan had in mind a more typical (and reasonable) definition (e.g. no drop in contrast at Nyquist due to diffraction that is visibly noticeable after a small amount of sharpening) -- which is what others said in the thread.

The size of pixel doesn’t limit anything. Digital sensor and film have no difference here.

Say someone is shooting f/64 macro photos on their 6 MP rebel and upgrades to a 7D in order to take advantage of the smaller pixel size. They will be in for a shock when they see that the modern 18 MP images are no more detailed than their ancient camera.





Contrast that with the example of a photographer who shoots portraits at f/5.6. When he upgrades from the 6 MP Rebel to the 7D, the linear resolution can be almost doubled.





Between the two examples is someone who shoots at f/22. There will be an increase in resolution, but since f/22 is narrower than the DLA of the 7D, returns will be diminished.
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