Originally posted by Marc Sabatella I too remember nothing in any Pentax manual about entering the longest focal length. And I can absolutely verify from experience that inputting too long a focal length can produce images that are obviously much worse than not using SR at all. But not if you only overstate focal length by a little - you have to be off by a lot before it makes matters worse. Entering 200 when you are really shooting at 50 would probably count, but I've noticed it primarily when entering 200 if I am actually shooting at 28. Entering 200 if you are really at 150 would probably be fine - although not as good as actually entering 150.
Of course, as far as I know, there are no 50-200 manual lenses out there - the 50-200's from Pentax are all AF and communicate focal length automatically.
Also, the topic of using older lenses on a DSLR comes up maube 3-4 times a week. i recommend browsing the forums for other discussions of the topic, including references to how to make the aperture ring work with a DLSR, and the change in field of view you will see when using a lens on digital versus film (aka "crop factor").
Tokina made a 50-250 f 4-5.6 AT-X lens; there was also a Sigma 50-200, 55-200, and others (Sakar, Soligor). A good listing of manual focus PK lenses is here (Bigma is on the list too for some reason, but that would communicate data to the camera):
35 mm MF zoom lenses Originally posted by billtin59 After actually looking this up in the K20 manual, pg 67, (as opposed to using my memory), it says "When using a zoom lens, select the actual focal length at the zoom setting in the same manner." It also goes on to explain that shooting distance influences SR as well. I suppose you could take this to mean when the lens is zoomed all the way (my initial interpretation), or you could take it as meaning whatever focal length you happen to be shooting at the moment, which seems impractical at best, and defeats the purpose of a zoom somewhat, don't ya think??
I have an old 80 - 200 zoom, and I input "200" and haven't had any problems at any focal length. to me, using the longer end covers you no matter where you are in the zoom range.
I seem to remember that chipped lenses "read" the make-believe "conversion factor" focal length as opposed to actual. I don't have any of the new lenses, so I can't verify this, but you might be getting away with a "200" SR setting because the camera (if the lens were "chipped") would assume it's a 120-300 as opposed to an 80-200. Anyone care to verify with a DA zoom?
Originally posted by Marc Sabatella It's not that setting to 200 "covers" yu if shooting at 80 - it's that it actually causes the sensor to *overcompensate*. I'm not sure if it would do so enough to to make the image worse than turning off SR, but it would probably come very close; if nothing else, it probably cancels out most if not all the advantage SR would otherwise have given you at 80. Try some tests with and withlout SR while shooting at 80 versus at 200. If you have the SR focal length set to 200, my guess is that you'll see SR giving a lot of improvement when actually shooting at 200, but not when shooting at 80.
And yes, you're right, it makes shooting manual zooms with SR a pain, which is why I don't bother buying manual zooms. But for those who do, better results would probably be obtained setting SR somewhere in the middle of the range - so that it doesn't overcompensate *too* badly at 80, and some compensation at 200 is better than none. Either that or set SR to 200 on the assumption that you'll most be using it at that end, but if you find yourself shooting at 80, you might be better off simply turning SR off.
Shooting with manual zooms is a snap, just like it always has been. Simply turn SR to "off," mount your camera/lens to your tripod and shoot, thereby giving you better than shake "reduction" - you get shake "elimination."