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08-17-2011, 07:30 PM   #1
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Join Date: Jul 2009
Location: Clinton, CT
Posts: 10
Finally got a K20D body

I haven't posted in here in 2 years, so let me RE-introduce myself: My name is Bart Brown, I'm now retired, and I live on Connecticut's Fabulous Vacation Shoreline.

When I was last in here, i was wandering around with a Pentax PZ-1 film camera, with the following lenses:
SMC FA 28-80 Power Zoom
SMC FA 100-300 Zoom

This past week, I scored an excellent Pentax K-20D body that honestly looks like it was never used. Shutter activations in the 2000+ range.

Is there a general article or FAQ here that will tell me what to expect with these AF lenses mounted on the K-20D? I realize these lenses will be crippled in some respects, but I'm not quite sure to what extent. If all I lose is the AF, that's great, as I much prefer manual focus, and always used my PZ-1 in that mode.

Also, I see a lot of postings, on eBay and elsewhere, about a "prime" lens, and it usually seems to be something like the old, but absolutely like new SMC PENTAX-M 50MM F2.0 I have. By "prime lens," is it meant that this is the lens you'd normally have mounted on the body for everyday shooting situations?

Finally, I'd really appreciate some input on the focal length difference between a DSLR and a film SLR. I read something to the effect that the ratio was 1.5:1, so that a film 50mm lens would be equivalent, on a DSLR, to 33mm, and a film 28mm would be equivalent to a DSLR 18mm. Is this true across the board, and are there problems to watch out for like image distortion at a FL of 18mm?

If there's a general article covering these points on the site, could someone please point me to them? If not, I welcome any and all advice.


Bart Brown

08-17-2011, 08:13 PM   #2
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Join Date: Dec 2007
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Hi bartbrn, welcome home.

So jumping in... my understanding...

Crippled... Usually referring to the lens being without an aperture ring. However, your question was put about the AF lenses on the K20D being crippled. If you meant manual lenses on the K20D then the you figure M42 (w/ adapter), K and M family lenses are limited in a sense that the automation in the camera is not full and no indicator for selected aperture in viewfinder nor all modes available. It is still easy enough to use with the green button in manual. A, FA, FA-J, DA have the electrical connection you to take advantage of the aperture priority mode and selected aperture is viewable, but A family of course is not an auto-focus.

Prime lens... usually the interpretation from "fixed focal length" I forget the origins... so could leave it so saying it is opposite of zoom.

1.5, the crop factor... Full frame or 36mmx24mm was the 35mm film, but the APS-C is smaller or about 24mmx16mm. The narrower viewing area of the lens seem almost closer. So you would multiply the mm size of the lens by 1.5 to figure out the K20D point of view for magnification. Or you figure in the world of 35mm film, 50 is normal and above is telephoto and below is wide-angle. So in the K20D or APS-C sensors cell point of view, 33mm is normal... 28 would be more like 42mm.

Hope that gets you off to a start?

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