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06-05-2010, 11:28 PM   #1
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Manual focus lenses on K7

How well have older, manual focus lenses worked on the K7, especially the 300mm f/2.8?

06-06-2010, 12:35 PM   #2
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That's a pretty broad question. Can you be more specific about what you are wondering? Something abut the K-7 in particualr you are thinking might differ from other DSLR's in some respect? There are tons of threads on old lenses in general (although relatively little on any 300/2.8's!). The K-7 is reported to meter somewhat better than the K10D and K20D which had some issues due to their focus screens. Aside from that, manual lenses work with the K-7 just as they do with all other Pentax DSLR's - which is to say, as well as the lens itself is capable of.
06-07-2010, 10:55 PM   #3
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I have the 300mm f2.8 lens from sigma. It is af lens. But several times i have tried to manual focus thru trees and such. I cannot ger a sharp pic with the k-7. I cannot get a proper adj on the eyepiece. Now the k-20 is different. It is easy for me to use because it lets me adj. the viewfinder sharper.
I hope that helps
Personally I think the af is very valuable and try to use it at all times. But i know there are times when you can't.
06-08-2010, 04:52 AM   #4
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Is the question how easy is it to achieve focus, or more in general how do the lenses perform with respect to resolution image quality etc.

I use a lot of MF lenses and I have found that the only sure way to achieve focus is to have a split image finder.

When my K10D failed I got a K7, but also got the K10D repaired and installed a split image finder, the K7 is my AF body the K10 is my MF body,

while I have taken great shots using MF lenses with both cameras, the split imagefinder, combined with generally fast manual focus primes is a joy to use.

When using stock viewfinders the DOF of the viewfinder exceeds the lens, especially fast lenses, so what looks in focus is not always perfect. Also Very fast lenses can be a little soft wide open and as a result the image may ot be as sharp as you think it should be. Add on to that, you need to have the eyepeice diopter set perfectly, MF can be a challenge, hence the split image finder. I think if you do a survey of forum members, most who do a lot of MF work use a split image.

One additional point, with respect to manually focusing AF lenses. This may not be the case every time, but I have found that the manual focus throw on many of my AF lenses is very short. My sigma 70-200F2.8 has 90 degrees focus throw to go from infinity to 6 feet. By comparison my Vovotar series 1 70-210 F3.5 is 180 degrees and my SMC Pentax 300F4 is over 300 degrees. Manual focus, specifically precise focus requires a gradual focus not a fast focus. 180 degrees of my vivitar is a good compromise for a one touch zoom, but I like a more gradual throw especially on long lenses.

there is another part of the question I missed until I re-read marc's response, and that is metering. for KA lenses metering is pretty good but for K mount lenses (with no A setting) metering on the Later bodies K10D, K20D, and K7 to a lesser extent is a little "interesting" to say the least.

06-08-2010, 09:37 AM   #5
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QuoteOriginally posted by garyk Quote
I have the 300mm f2.8 lens from sigma. It is af lens. But several times i have tried to manual focus thru trees and such. I cannot ger a sharp pic with the k-7. I cannot get a proper adj on the eyepiece. Now the k-20 is different. It is easy for me to use because it lets me adj. the viewfinder sharper.
Is the diopter control on your K-7 defective, perhaps? It should be possible to adjust it just as the K20D. Manual focus on the K-7 shouldn't be any more difficult than the K20D. The viewfinder is only the tiniest bit smaller (but gives 100% coverage, which is a nice plus).
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