StanMac Loc: Tennessee

I need an ultra wide angle (UWA) lens for my K5 for use on a project that I took on. The K5 being an APS-C camera, I have looked at the Pentax DA 12-24mm and the Sigma 10-20mm EX DC HSM zooms. The Pentax is way out of my affordability range. The Sigma is possibly within my reach, but it has its own focusing motor. I’m thinking that if I could find a lens without a focusing motor, the lens may be even more affordable. Is there another UWA in a Pentax mount that uses the in-body auto-focus motor of the K5? I haven’t been able to find anything on Google searches – I’m not very astute at constructing a google search query, I guess.

If there are no other Pentax mount AF lenses without in-lens focusing motors, I guess I’ll have to go with the Sigma 10-20mm with its HSM motor. Which raises another question. If I use the Sigma with its own HSM focusing motor, how will it interact with the K5’s auto-focusing function? Will the lens motor override the in-body motor or vice versa? The K5 in-body motor functions through a screw-drive connection in the mount. If the Sigma lens mount doesn’t have a matching connection socket, will the in-body focusing motor free wheel as the camera tries to focus? Or will the in-body motor be deactivated by the lens by way of information sent to the camera through some electrical contacts? Looking at the mount end of the Sigma I don't see a screw drive socket, but I do see two electrical contacts that appear as though they may mate with two contacts located in the lens throat of the K5. Are these the connection points for disabling the in-body focusing motor and controlling the lens focusing motor? My other Pentax lenses and Sigma 70-300mm DL Macro in Pentax mount don’t have those extra electrical contacts – only the ball contacts on the mount flange itself.

Thanks to you Pentaxians out there on UHH that can help me clarify this information. My apologies for being too wordy.

Stan

rehess Loc: South Bend, Indiana, USA

(1) Pentax bodies function perfectly fine using lenses which have in-lens motors. I have their 18-135 lens, and there is never a problem with my K-30 starting it's motor

(2) I have the f/4-5.6 version of the Sigma 10-20mm lens.
http://www.uglyhedgehog.com/t-446161-1.html
I believe it is out of production, but you may be able to find one somewhere. From my perspective, it is a fine lens, and you might be more comfortable with the fact that it uses the in-body AF motor.

lamiaceae Loc: San Luis Obispo County, CA

Is there some reason you must have an Autofocus lens? The "Ball Contacts" are the regular electrical contacts. They had those since the film A-series cameras and lenses of the mid-1980's. The newer Pentax DSLRs also have other contacts inside the mount for the silent motor system in the lenses that have them. But you don't need those.

Could this new manual 10mm f/2.8 $379 lens work for you? https://www.adorama.com/sy1028px.html Or look for a vintage used WA Pentax lens, say a Pentax A, F, FA, DFA lens.

GENorkus Loc: Washington Twp, Michigan

If you don't mind using a manual prime, look into the Rokinon lenses, (made by Samyang Optics).

For my three Pentax cameras, I recently picked up the 8mm F3.5 HD with removable hood for $270 from B&H and understand it's less now. So far I have only praise about the quality of it and the photos.

Rokinon have glass in a bunch of different ultra wide and wide angle lenses, and other sizes too. See any major camera shop to check them out.

http://rokinon.com/lenses/digital-photo-lenses/searchby/mount/pentax-k

Mundj Loc: Richmond TX

I have a Tamron 10-24 mm that has worked well for me on my K-7 and K-3. It utilizes the camera screw drive system. There are several reviews available on Google. Adorama is selling one for less than $400.

God luck and what ever your choice have fun and try to avoid including you feet in the Photo. 😜

StanMac Loc: Tennessee

Thanks for all your replies and suggestions. I'm thinking I'd really rather have the flexibility of a zoom. The photos you posted, Rehess, shows the Sigma provides the field of view I'm going to need so I'm starting my search for the Sigma 10-20mm f/4.0 with the online retailers and auction sites. Wish me luck!

Stan

rehess Loc: South Bend, Indiana, USA

Good luck!

{I purchased mine used from a Pentax Forum member via their Marketplace}