Help a novice: sharp or unsharp images? Should I return my X-T30?

Started 3 months ago | Discussions thread
photonut2008
photonut2008 Veteran Member • Posts: 6,088
Re: Lens testing

jrtrent wrote:

From the calculator at Cambridge in Colour I see that diffraction limits change with increasing resolution. My 6 mp DSLR is not diffraction limited at f/11, but the OP's 26 mp Fuji is already diffraction limited at f/8.

Diffraction limited is really a misused term; I would instead say diffraction impaired. To say a sensor is diffraction limited at f/8 it would have to have 240 lp/mm, which works out to 88 MP on a DX sensor.

If my D500 was diffraction limited at f/13 then the most I could resolve with it using a 35mm lens at that f/stop would be about the same as I can resolve using a 90mm at f/32 (because the aperture diameters of those two lenses at those two f/stops are about the same size):

What I got was color moiré from the 35mm lens at f/13, and that means I am not diffraction limited at f/13 with that lens, I'm resolution limited.

How does this translate to comparative results? For example, I just don't get the depth of field I want most of the time at f/5.6, so I'm going to stop down to f/8 and even f/11 on occasion. Does the fact that I'm not diffraction limited at those apertures with my old camera mean its output is going to look better than if I used those same apertures with the OP's kit, or will the newer camera still produce better output at those apertures despite being diffraction limited?

Here is a comparison I did years ago between my D70 and my D300:

Again, resolution is the limitation, diffraction is an impairment. You can deal with the impairment by increasing local contrast and other sharpening techniques, and how much of that you apply will depend on your intended output (same as calculating DOF depends on viewing distance).

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 photonut2008's gear list:photonut2008's gear list
Nikon D800 Nikon D500 Nikon AF-S Nikkor 70-200mm f/2.8G ED VR Nikon AF-S DX Nikkor 16-85mm f/3.5-5.6G ED VR Nikon AF-S DX Nikkor 35mm F1.8G +14 more
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