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08-02-2008, 04:47 PM   #1
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Location: Northumberland, England (Gt Britain)
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Using manual KA lenses with a K20D

Mods, please move this if appropriate, I've read the Knowledgebase threads about using M42 M and K lenses (and the one about KA lenses on *ist), however, it states:-
Please remember that questions are not to be posted in the Knowledgebase. Please only post articles or useful resources pertinent to Pentax.
so I'm starting here.

I have a significant collection of Pentax manual focus KA (and K) fitting lenses (that I use with Super A 35mm cameras fitted with motor-drive As).
I'm predominantly interested in aerial displays at airshows, and I'm therefore used to following fast-moving objects (albeit at a distance), although I also 'shoot' birds. I use rifle-stocks with a monopod to support long-focus lenses. Otherwise (ie when not at airshows) my standard-fit lens is a Vivitar 28-200mm (useful for static shots in aircraft museums - although I had to resort to the 18-28mm to get the Airbus A380 into frame!)

I am considering buying a K10D or K20D body so that I can take digital images as I shoot 6 to 10 36-exposure rolls at each show (I don't believe that the K100D or K200D will allow rapid-enough repeat rates for action shots).

I realise that I will not get autofocus, but, if I set the lens to 'A' will the exposure be correctly computed?
Can you give me a summary of the facilities (and limitations) that I can expect?

I read (elsewhere on this forum) that the SAFOX VIII AF system may not be 'state of the art' and I wonder whether for my application that manual focussing might be preferable (even with dedicated autofocus lenses)?
As I already have a wide selection of both prime and zoom lenses (all manual focus of course) I'm even wondering whether to opt for 'body only' . . .
. . . apart, perhaps, from getting a Bigma 50-500mm . . .

Does the image-stabilisation work with all lenses?
What are the disadvantages associated with using the image-stabilisation mode?

Are there any physical limitations restricting fitting manual KA (and K) type lenses (I have lenses from 16mm to 1000mm)?

08-02-2008, 07:50 PM   #2
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Welcome to the forum!

With 'A' lenses, you will get center-weighted metering. with K lenses, you have to set it to manual and press the little green button (on the K10/20) to step the lens down and meter any time you want to take a reading (also center-weighted). It sounds like you're used to a center-weighted system, so that shouldn't be a problem.

While others here have more experience with the SAFOX system in fast-action photography, I will say that while it's no D3 or 1Ds Mk III, it still is a good system. Don't discount it yet

Image stabilization will work with any lens that mounts on the camera. However, on pre-F lenses (K, A) you have to manually input the focal length via menu. This can be a little problematic with zoom lenses.

The K100/200 aren't much slower than the K10/20 in burst mode- it's something like 2.8 fps vs 3 fps. The K10/20 will allow you longer bursts, though.

The only physical limitations I've run across with K-mount lenses is that some 3rd party lenses can get jammed on the AF drive screw. I've heard the Ricoh k-mount lenses have this problem, and I had to take a hacksaw to get an Albinar 70-200 f/3.9 zoom off my ZX-L. I've not heard of any other problems.

For a more in-depth discussion, see Bojidar Dimitrov's page on the K-mount. His site is full of great info.
08-02-2008, 11:50 PM   #3
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Join Date: Mar 2008
Location: England UK
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QuoteOriginally posted by clawhammer Quote
Image stabilization will work with any lens that mounts on the camera. However, on pre-F lenses (K, A) you have to manually input the focal length via menu. This can be a little problematic with zoom lenses.
In the time-and-effort sense, yes, but it's not difficult. The prompt to enter the focal length appears on startup (presume the K20D is the same as in this respect), so switching the camera off-and-on is my normal approach for my zoom lens.

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