Tilted copy of the 50/1.8 S

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JimKasson
JimKasson Forum Pro • Posts: 22,412
Tilted copy of the 50/1.8 S
8

I just picked up a 50 mm f/1.8 Nikkor S. The first thing I do with a new lens is put it through my lens screening test.

Here's a sample full frame image, lens wide open and target about 50 meters away:

It looks dark because I exposed the target. Here's a 200% enlargement of the star placed in the center, all four corners, and all four sides:

You can see there's quite a bit of light falloff off-axis. This is not unusual for fast lenses. The top row is much sharper than the bottom. The left bottom corner is especially affected. Is this general softness in that region, or is it field tilt? We can find out by focusing on that corner:

That's plenty sharp. So the lens is tilted. Since I don't intend to use this lens for flat-field work, this will not be a problem for me, and I'm keeping the lens. However, when I do my tests, I'll make sure to focus on the location in the image in which I'm interested.

Jim

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