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Testing C-Mount lenses on NEX

Started Aug 23, 2011 | Discussions thread
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Testing C-Mount lenses on NEX
Aug 23, 2011

Hi, I have a NEX-5 since Dec' 10 and enjoyed using it with the kit lenses until now and have just started using manual lenses (or am about to start as the adapters just arrived this morning).

I also happen to work in Machine Vision for a large industrial camera manufacturer. As these cameras mostly uses a C-Mount I have tens of C-mount lenses lying around in the office that I plan on testing with the NEX. I expect most of them to be crap (and not covering the full sensor) but I may have a few gems in the lot like some 25mm f1.4 made for 2/3" 5Mp sensor (3.45 x 3.45µm pixels) which should be plenty sharp on the NEX or an old Fujinon TV zoom 12.5-75mm with a constant aperture of f1.2.

I just received the C-Mount adapter this morning (the cheapest one on eBay) and I have a few question before starting to test some of the lenses.

  • What's the position of the NEX shutter relative to the e-mount? Some C-Mount lenses have a protruding rear element that extend beyond the C-Mount and I'd like to avoid the shutter getting damaged by hitting the rear of lens. The C-Mount registering distance is already shorter than the e-mount and I'm affraid that with some lenses the rear element may be sitting too close to the shutter.

  • Any kind of recommendation for testing the relative quality of the lenses? What should I look for when testing the lenses? I'll check the size of the image circle of course and how it covers the APS-C sensor and if there is any vignetting/light fall-off. I have a few test charts and pattern boxes in the office that I can shoot to test the sharpness. Any other things I should look for?


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