Nikon Z 35/1.8 S - hard to find a well centered copy?

Started 4 months ago | Discussions thread
1llusive
1llusive Veteran Member • Posts: 3,397
Re: Nikon Z 35/1.8 S - hard to find a well centered copy?

kenw wrote:

1llusive wrote:

kenw wrote:

Probably different standards and different ways of using the lens would be my best guess!

I think a good example of that would be something like the Samyang/Rokinon 135/2 which is a hit both with the portrait photography crowd and the astro crowd. The astro crowd finds a lot more "bad" copies because every photo they take of the sky near wide open is essentially a very sensitive test for "decentering". Meanwhile the portrait crowd is going to say all their lenses are just fine because of course the corners and edges of all their photos are out of focus anyway.

As you mention in your other post, beyond any reasonable distance you start to get blurring from the air. So while a shot of a star field seems to be an ideal test, I think shutter speeds need to be very short and I think several images need to be taken and analyzed to be sure you aren't knocking a lens corner when it's just the atmosphere.

Pointing up into the sky and pointing along the surface of the earth have dramatically different seeing profiles (along the surface of the earth is far, far, far worse). So while 100mm is often problematic pointing at a distant terrestrial target it is not often an issue pointing up at the zenith. But still, seeing varies *a lot* from night to night and the location you shoot an astro photo also impacts your local seeing a lot as well.

On a Z7 with a 100mm lens a pixel has about a 9 arcsecond angle of view (unless I screwed up the math). Seeing limits of 9 arcseconds at zenith are incredibly bad and are actually beyond the lowest seeing rating of typical scales used to grade astronomical seeing. So it sure seems like down around 135mm a star field near zenith is a perfectly reasonable test target? Or did I make a mistake somewhere?

What about wider focal lengths?

 1llusive's gear list:1llusive's gear list
Nikon Z6 II Sigma 100-400mm F5-6.3 Nikon Z 24-70mm F4 Nikon Z 85mm F1.8 +1 more
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