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p.1 #1 · p.1 #1 · Pentax 67 lenses on Sony A7r -- are you seeing shutter vibration? | |
I'm looking for insights from people who are using Pentax 67 lenses on Sony A7r cameras (not A7, A7 II or A7r II). I'm specifically interested in how the 55mm f/4 Pentax 67 lens is affected by the A7r shutter vibration problem -- but experiences with other Pentax 67 lens are welcome (e.g., 75mm and 90mm primes, 55-100 mm zoom).
I won't be moving to an A7R II for a while, if ever, so I need to get the most from my A7r. That means managing shutter vibration. I've been testing extensively during the past week and now have a good idea how my own equipment is affected. All of the following results are in portrait orientation (which I find myself using very often). Note that with the Canon FD lenses, the camera mounts to the tripod on its L bracket. With the Pentax-A lenses, I'm using dual Mirex adapters, and the first Mirex adapter is mounted to the tripod; the camera hangs off the second adapter. This is of course the ideal "worst case" scenario for A7r shutter vibration!
* Among my Canon FD lenses, the FD L 20-25 f/3.5 and the FD 17mm f/4 are not subject to the vibration problem on my setup at any shutter speed. However, the 50mm f/1.4 and the 100 mm f/2 are extremely sensitive from 1/125 second to 1/4 second. All my FD lenses are perfectly fine on my Sony A7.
* I have three Pentax-A 645 lenses that I use on my A7r with dual Mirex adapters. (Results are the same on my Fotodiox P645-NEX adapter, so it's not the Mirex adapters.) The Pentax-A 35mm is totally immune to vibration problems based on my tests. The Pentax-A 45-85mm is fine at 45mm, but shows blur increasingly strongly towards 85mm in the range of 1/125 to 1/4 seconds. The 150mm shows it very strongly too.
For the lenses that show vibration issues, I use Joseph Holmes' "deadweight" solution; a deadweight clamps to the L-bracket and absorbs the virbration. It's a bit kludgy, but it works.
I'm intrigued though that the 35mm Pentax-A lens is not affected at all, whereas my Canon FD 50mm is severely effected. Would big, heavy Pentax 67 lenses (in particular the 55mm f/4) behave like my 645 35mm lens, in other words, focal length short enough and lens heavy enough that it's not affected by vibration. I use the 55mm focal length a lot; it would be nice to have one more lens where I don't need the deadweight. If the 75mm and the 90mm are also unaffected, I could avoid the deadweight most of the time...
Rob
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