Strange A7 image anomaly with telephoto lenses

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WoodWorks
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Strange A7 image anomaly with telephoto lenses
10 months ago

I've recently acquired a couple of telephoto lenses, a Canon FD 100-300mm f/5.6L and a Nikon 180mm f/2.8 AIS ED to use with my A7, and both of them exhibit a strange pattern on their images, especially when stopped down. You can see it most clearly on this image of the clear sky shot with the Nikon @ f/13. I upped the contrast a little in Lightroom to enhance the effect.

Nikon 180mm f/2.8 AIS ED @ f/13

But it's also visible on this shot with the Canon lens, which I think was shot at f/11.

Canon FD 100-300mm f/5.6L @ f/11

Both lenses have the OEM hoods, so that's not the issue. Neither has a baffle in the back, so that's out as well. Neither had any filters mounted to them. Both obviously have different adapters. And I've now tried two different copies of the Nikon, and both exhibit the same problem. In fact, the Nikon starts to show the two, light, bracket-shaped areas at any aperture higher than wide open @ f/2.8.

None of my other, shorter lenses show this flaw, including my Canon FD 85mm f/1.8. So it seems to happen only with longer focal lengths.

Has anyone else encountered this with their A7 or A7R, or care to speculate as to the cause?

David

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