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12-12-2007, 09:43 PM   #1
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Pentax medium format lenses on a DSLR?

Has anybody tries these with an adapter? It sometimes seems that used Pentax medium format lenses could be had cheaper than 35mm stuff. Is there something to be aware of before getting these? Will a 300mm still be 300mm on a K100D for example?

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Boucicaut

12-12-2007, 09:59 PM   #2
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I don't think the focal lengths will be the same. Also be aware that it will be full manual everything. You should get extremely good IQ because you definately would be shooting in the 'sweet spot' of the lens (right in the center of the image circle). If you can, try it out. I'd love to hear how it works.
12-12-2007, 10:35 PM   #3
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Yeah, it would be cool beacuse I always see 645 lenses for auction at yahoo japan at decent prices.
12-12-2007, 11:14 PM   #4
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QuoteOriginally posted by clawhamemr Quote
I don't think the focal lengths will be the same. Also be aware that it will be full manual everything. You should get extremely good IQ because you definately would be shooting in the 'sweet spot' of the lens (right in the center of the image circle). If you can, try it out. I'd love to hear how it works.
The focal lenth will be the same, it's 300mm. The adapter puts the lens in the correct position to focus to infinity. A caveat would be that medium format lenses do not necessarily resolve the same degree as a smaller image circle lens. It's not needed when the negative is 6 x 7 cm, the magnification ratio is so much less. Also the lens design is somewhat different - the elements have to cover an image circle nearly 5 x the diameter. That is a super challenge for the lens designer.

12-12-2007, 11:30 PM   #5
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QuoteOriginally posted by clawhamemr Quote
I don't think the focal lengths will be the same. Also be aware that it will be full manual everything. You should get extremely good IQ because you definately would be shooting in the 'sweet spot' of the lens (right in the center of the image circle). If you can, try it out. I'd love to hear how it works.
Manual doesn't bother me that much. Manual focusing is fine by me and I use aperture priority a lot anyways, so all is good. What worries me though is will I get a similar angle of view as I would with a normal 35mm lens, i.e. will a 300mm 645/6X7 lens give me the same reach a 35mm format 300mm lens would? If this works, I may try to do it. Don't worry, I'll report back if I go through with it

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12-12-2007, 11:31 PM   #6
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QuoteOriginally posted by Boucicaut Quote
Manual doesn't bother me that much. Manual focusing is fine by me and I use aperture priority a lot anyways, so all is good. What worries me though is will I get a similar angle of view as I would with a normal 35mm lens, i.e. will a 300mm 645/6X7 lens give me the same reach a 35mm format 300mm lens would? If this works, I may try to do it. Don't worry, I'll report back if I go through with it

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Boucicaut
The 300mm focal length will give you the same angle of view as a 300mm made for the 35mm format. It just doesn't use the whole image circle. You can be 200% guaranteed not to have any vignetting!
12-12-2007, 11:32 PM   #7
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QuoteOriginally posted by Canada_Rockies Quote
The focal lenth will be the same, it's 300mm. The adapter puts the lens in the correct position to focus to infinity. A caveat would be that medium format lenses do not necessarily resolve the same degree as a smaller image circle lens. It's not needed when the negative is 6 x 7 cm, the magnification ratio is so much less. Also the lens design is somewhat different - the elements have to cover an image circle nearly 5 x the diameter. That is a super challenge for the lens designer.
Thanks. This is something to consider, especially regarding the upcoming K10D replacement with it's 14mp sensor. I would imagine that the resolving power would be enough for a K100D Super though.

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Boucicaut
12-12-2007, 11:33 PM   #8
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QuoteOriginally posted by figmental1978 Quote
Yeah, it would be cool beacuse I always see 645 lenses for auction at yahoo japan at decent prices.
Do you have experience of buying from there?

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Boucicaut

12-17-2007, 03:23 AM   #9
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Medium format lens plans on hold for now...

...because I ordered a vintage/retro 400mm f6.3 Komura (m42) so I won't need another long tele for a while (unless the Komura turns out to be a complete bust, of course).

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Boucicaut
12-18-2007, 06:30 PM   #10
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Yeah, I've bought some stuff through Yahoo Auctions Japan and Rakuten. But I don't think they send internationally, domestic orders only.
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