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04-13-2010, 10:02 AM   #1
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645 lenses on k-mount experience

Can anyone share their experience using 645 lenses on k-mount. Someone is selling me Mamiya 80mm/2.8 for just $50 and was wondering if it is worth it. As I read in other forum, 645 lenses are not as sharp as 35mm but I have no clue or experience and hence I am seeking advice here.

Also, how the focal length & aperture of 645 lenses maps to APS-C DSLR. In other words, what is the equivalent lens in APS-C, would 645 80mm lens act as 80*2.6*1.5 = 312mm on APS-C DSLR?

Thanks.
Yusuf


Last edited by yusuf; 04-13-2010 at 10:29 AM.
04-13-2010, 10:15 AM   #2
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QuoteOriginally posted by yusuf Quote
Also, how the focal length & aperture of 645 lenses maps to APS-C DSLR.
Focal length and aperture is independent of the film/sensor format.
04-13-2010, 10:34 AM   #3
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its a 120mm f2.8 lens on aps-c
04-13-2010, 10:37 AM   #4
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QuoteOriginally posted by eigelb Quote
its a 120mm f2.8 lens on aps-c
hmm, may be I am missing something but how can it be 120mm?

04-13-2010, 10:47 AM   #5
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yusuf, 80mm lens is always 80mm lens no matter what is the sensor size. On 645 it will have angle of view close to 50mm on 36x24 frame and on aps-c the angle will be about 120mm lens on 24x36 film frame.
04-13-2010, 11:11 AM   #6
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A review of the 80mm 2.8 at a Canon 5D:
Mamiya 645 80mm f/2.8 Lens Review
04-13-2010, 12:31 PM   #7
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M645 lens

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/96854-diy-mami...s-adapter.html

Link includes a comparison pix of Mamiya 55mm and 80mm with Tamron 28-75.

Be prepared to acquire or build a lens adapter and note that the lens will operate as a Pentax M-class lens with the exposure issues common to that type lens. You'll need ~ 17.8mm of extension between the camera mount and lens base to focus to infinity.

H2


http://www.pbase.com/image/123455997.jpg

Last edited by pacerr; 04-13-2010 at 12:36 PM.
04-13-2010, 10:24 PM   #8
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QuoteQuote:
yusuf: As I read in other forum, 645 lenses are not as sharp as 35mm but I have no clue or experience and hence I am seeking advice here.
Don't speak until you have tried them. People told me this about using 6 x 7 MF on K-mount too. But I tried it and got some nice results. Sharpness is on a par with my 35mm lenses, other things are better---some shots in here:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/96253-new-pent...m-f-5-6-a.html

Sorry, but I needed to remove most of the pics from here:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/96253-new-pent...m-f-5-6-a.html

04-14-2010, 02:47 AM   #9
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You should also try to take into consideration the price of an adaptor from the 645 lens mount to K-mount...

Last time i looked that cost around $100... maybe more, maybe less...

Which to me is a bit insane :P
04-14-2010, 03:14 AM - 1 Like   #10
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not recommended. why? because you won't be able to take full advantage of an Medium format lens' real capability and potential. plus you would need to find some adaptors that would enable the lens to fit, work and focus at infinity, plus it would be quite of a hassle or require a bit of work dealing with such converted lens. full-format m42 and K-mount lenses are an exception since they work fine on a K-mount cameras.

if you really want to use an MF lens, you have to buy an MF body.

as far as sensor cropping is concerned, sensor crop doesn't mean it would magnify or increase the focal range of a lens. it would merely cut out some portions of the FOV that have an appearance or equivalent value of a particular sensor size. in short, sensor cropping is based on FOV measurement, not focal range measurement.

that's why when you put a 50mm FF lens on an APS-C dlsr, it would say 75mm equivalent on a 35mm format.

*note: DA lenses are cropped the same way as FF lenses on an APS-C sensor. so don't think that a DA14 would still be 14mm. it would still be cropped. I just hate it when they always make a 35mm equivalent conversion and cause a lot of confusion. instead of putting DA14, they could just simply written or disclosed it as a 21mm since it works that way and doesnt work on a FF slr due to vignetting and lens design, and spare us from any misconceptions everytime.
04-14-2010, 07:24 AM   #11
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QuoteQuote:
Vylen: You should also try to take into consideration the price of an adaptor from the 645 lens mount to K-mount...

Last time i looked that cost around $100... maybe more, maybe less..
Yes, the price seems too silly, but the adapter for 67 medium format to K-mount can be bought for almost half--not sure why this is.

QuoteQuote:
Pentaxor not recommended. why? because you won't be able to take full advantage of an Medium format lens' real capability and potential. plus you would need to find some adaptors that would enable the lens to fit, work and focus at infinity, plus it would be quite of a hassle or require a bit of work dealing with such converted lens. full-format m42 and K-mount lenses are an exception since they work fine on a K-mount cameras.
I find I get exceptional use out of at least a couple of MF lenses on my crop sensor. In particular, my 6 x 7 165mm 2.8 makes a very nice 330mm 5.6 with my SP F MC7 Tamron adapter. It is lighter than my SMC 300 f 4, close focuses much better than the SMC 300 f4, is sharper than the SMC 300 f4, it is shorter than my SMC 300 f4, it has a tripod mount which my SMC 300 f4 does not have. It even has a little more reach than my SMC 300 f4--and the SMC f4 was alreadt one of the best bargain 300mms out there.

And, it cost me a lot less than did the SMC 300 f4. Take a look in here, for example:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/96253-new-pent...m-f-5-6-a.html
04-14-2010, 08:43 AM   #12
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QuoteOriginally posted by Jewelltrail Quote
Yes, the price seems too silly, but the adapter for 67 medium format to K-mount can be bought for almost half--not sure why this is.



I find I get exceptional use out of at least a couple of MF lenses on my crop sensor. In particular, my 6 x 7 165mm 2.8 makes a very nice 330mm 5.6 with my SP F MC7 Tamron adapter. It is lighter than my SMC 300 f 4, close focuses much better than the SMC 300 f4, is sharper than the SMC 300 f4, it is shorter than my SMC 300 f4, it has a tripod mount which my SMC 300 f4 does not have. It even has a little more reach than my SMC 300 f4--and the SMC f4 was alreadt one of the best bargain 300mms out there.

And, it cost me a lot less than did the SMC 300 f4. Take a look in here, for example:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/96253-new-pent...m-f-5-6-a.html
although some MF lenses produce some very good results, I believe that he'd be better off with a 135mm FF lens and surely he could find a lot of excellent ones at a bargain as well.
04-14-2010, 09:37 AM   #13
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I use medium format lenses and think it is great fun. Are they practical? No, but who cares. I have often considered hunting down that fast mamiya 80mm f/1.9 lens to use on my k20D.
04-14-2010, 12:39 PM   #14
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QuoteQuote:
Stephen Merola: I use medium format lenses and think it is great fun. Are they practical? No, but who cares. I have often considered hunting down that fast mamiya 80mm f/1.9 lens to use on my k20D.
They can be practical as well as great fun. Seriously.

QuoteQuote:
Pentaxor: although some MF lenses produce some very good results, I believe that he'd be better off with a 135mm FF lens and surely he could find a lot of excellent ones at a bargain as well.
My 330mm f 5.6 cost me $88, shipped to my door. MF lenses have gotten very inexpensive. But, for most applications, I agree that FF, da, di lenses are the most logical way to go on crop-sensor. There are always exceptions of course.
04-14-2010, 01:27 PM - 1 Like   #15
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I use the P67 400/4EDIF, P645 300/4EDIF and P645 120/4Macro with Pentax adapter on my K mount Dslr. Those three lenses which I have are that good optically.
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