Leaf shutter not uniform?

Started Dec 7, 2012 | Discussions thread
OpticsEngineer Veteran Member • Posts: 5,958
Re: Leaf shutter not uniform?

As part of my job designing optical systems, quite a few times I have evaluated optics for decentered apertures.  (both on real systems and in raytracing software.)  In general, optical systems are not overly sensitive to apertures being decentered.  If a lens is good at f/4 centered, it stands to reason it would be good at f/5.6 slighty decentered.    The light is still going through some good glass.  I am sure the lens designers considered aperture decentration as part of the optical design tolerancing and they came up with some allowed values.  (it is pretty easy to do using raytracing software.)

Also be aware that you are looking at the aperture leaves through some lenses that probably create some magnification.  So the actual decentration is probably less than it looks.

The other thing to consider is that you are judging the centering relative to a mechanical housing.   The optical axis of the lenses may not actually be centered in that housing depending on what adjustments are made during the manufacture of the lens.

I would go ahead and do some testing to check the camera/lens out.  It certainly doesn't hurt.  I would include some shots of the clear blue sky at various aperture settings and inspect for non-uniform vignetting left/right/up/down.

But when I get lenses that look like that, I mentally file it into into the category of  "oh that looks interesting" and not the category of  "oh my gosh something is wrong."  Seeing pictures like that would not dissuade me from buying one of these by the way.

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