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07-30-2010, 03:04 AM   #1
emr
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67 vs. 645 lenses on a 645D body?

If we ignore the AF related aspects and the fact that a 67-645-adapter may not be easy to find, are there disadvantages in using 67 lenses on a 645D camera body compared to manual focus 645 lenses?

07-30-2010, 03:08 AM   #2
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The lenses would have no auto metering, and would be heavy as hell. Apart from that, no

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07-30-2010, 03:25 AM   #3
emr
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QuoteOriginally posted by Adam Quote
The lenses would have no auto metering, and would be heavy as hell.
Thanks. But I have a vague recollection of the adapter (gotta check this) relying the aperture setting, so wouldn't one be able to shoot in Av mode then?

I may be completely misguided, though.

EDIT:

From B&H website

QuoteQuote:
Pentax 67 Lens to Pentax 645 Body Adapter - Allows Pentax 67-system lenses to be used on the Pentax 645 body. Aperture-Priority AE 2, metered manual and TTL auto flash modes can be used.
07-30-2010, 06:38 PM   #4
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The 645 lenses may have better resolution than the 6x7 lenses of the same focal length since the 6x7 lenses need to have a greater image circle. Some lenses are remarkably even across the IC while others are noticeably sharper in the centre (a sweet spot). If you use a lens with a sweet spot on a format smaller than intended then you may end up with the entire image in the sweet spot and it will look blazingly sharp. If, on the other hand, the lens has been designed to be consistently sharp from edge to edge then the centre may have less resolution than the design with the sweet spot. The smaller the area you have to cover the easier it is to make it sharp. Usually the gains from the larger image area outweigh the losses in resolution, but if you are using them on the same size sensor then the 645 lens is more likely to be sharper. Eventually, with a bit of luck, someone will test a few of the 6x7 lenses against the 645 equivalents and we will know for sure.

Of course, the 75 shift and the 120 soft don't have equivalents in the 645 range, so they may be the only game in town if you need those abilities.

07-30-2010, 07:20 PM   #5
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Yes there are disadvantages. You negate the whole point of having an automatic camera. But on a more serious note, I'd want lenses made for it.
07-30-2010, 08:38 PM   #6
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I use the 67 300mm ED and 500mm on a 645N anytime I need a telephoto (I have 645 lenses in the shorter focal lengths). The 67 lenses behave as any manual A 645 lens does, although no A mode. The aperture is set with the aperture ring and the camera can be used in Av or manual mode. No difference except for the larger size of the 67 lenses. I've tested several 67 645 and 35mm lenses on a DS or 20D body and can see very little difference in performance between them. I think the belief that MF lenses are always inferior to smaller format lenses is something of a myth. There is no advantage to using the 67 lenses, unless of course you also use a 67 camera too.
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