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11-13-2013, 04:35 AM   #1
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Aetna Rokunar 70-210mm f/4 lens, c/y mount

G'day, mates. Would anybody know anything about this lens? It belonged to my late brother, and if I am not mistaken, he had this lens with him when he visited us in 1973. I am curious how good it is, considering that it has constant aperture. The lens is clean and looks almost new. I think it is all metal and glass as it is very heavy. Also, I would like to know the most cost-effective way to use this on my Pentax DSLR. I found a couple of adapters on e b a y but I cannot find any comments on them. Any information and advice will be greatly appreciated. Thank you and regards.

11-13-2013, 04:57 AM   #2
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There is a modification that involves shaving down the bayonet lugs to make it fit, but it shouldn't be used on long and heavy lenses like yours.

Without some form of mount modification you are not going to have infinity focus unless you get an adapter that has glass in it. This glass they use in the adapter works as a short teleconverter and will cost you some light and image quality, so it is not preferred. You can remove this glass and it will become a short extension tube, this will cost you infinity focus, but also allow you to focus closer. I haven't seen an adapter that comes without glass.
11-13-2013, 05:07 AM   #3
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QuoteOriginally posted by elliott Quote
There is a modification that involves shaving down the bayonet lugs to make it fit, but it shouldn't be used on long and heavy lenses like yours.

Without some form of mount modification you are not going to have infinity focus unless you get an adapter that has glass in it. This glass they use in the adapter works as a short teleconverter and will cost you some light and image quality, so it is not preferred. You can remove this glass and it will become a short extension tube, this will cost you infinity focus, but also allow you to focus closer. I haven't seen an adapter that comes without glass.
Hi Elliott. It doesn't look promising, does it? The lens really looks nice and it's a shame that it's not that user-friendly in my case. Thanks and best regards.
11-13-2013, 10:20 AM   #4
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Buy a Used Sony Nex and a adapter and go to town

11-14-2013, 01:18 AM   #5
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QuoteOriginally posted by Corto-PA Quote
Buy a Used Sony Nex and a adapter and go to town
Hi Corto-PA. I'm sorry but I can't understand your advice re going to town. English is not my first language. Thanks.
11-14-2013, 04:52 AM   #6
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Aetna Rokunar (Sun Optics) 70-210/4 Auto Zoom

it may come with YS interchangeable mount, in your case may be it is a YS-C/Y mount.
Try to find a YS-K mount (or YS-M42 mount) to use with pentax bodies
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