K20D: Getting 300 mm f2.8 to work on it

funinoz · 08-30-2008, 02:16 AM

I'm thinking of buying a K20D with the intention of using my m/f Pentax 300 mm f2.8 and 500 mm f4.5 lenses. Went to local camera shop to demo it and there appears to be no communication between camera and lens. Shows "F' in top display, won't shoot. Three staff members couldn't work it out, but I think they weren't Pentax experts.

Any suggestions? Am I missing something here?

Taff · 08-30-2008, 02:30 AM

are these manual lenses?

**wlank** · 08-30-2008, 02:34 AM

Originally Posted by funinoz

Any suggestions? Am I missing something here?

Read the manual. Pentax Imaging - Manuals & Literature

ftpaddict · 08-30-2008, 03:12 AM

If they're K or M-series (no "A" position on the aperture ring) K-mount lenses, they feature no electronic contacts on the lens mount, and therefore cannot communicate aperture information to the body.

Your K20D is not set up to allow use of aperture ring with older lenses. You can change that in your camera's custom menu.

Once you enable the appropriate setting, the camera will work properly.

Still, you'll have to twist the aperture ring manually, then press the green button (I think? I 've never owned a K20D), then fire away.

timk · 08-30-2008, 03:35 AM

dont forget to select manual focus with the lever

Taff · 08-30-2008, 03:36 AM

you got it FTP

marlon · 08-30-2008, 03:43 AM

that is correct. Enable the aperture option in the custom menu to not be "Prohibited" or whatever, and set it to manual focus and try again. Im using some embaressingly old lenses on mine.

*Syb* · 08-30-2008, 04:21 PM

The 300/2.8 (if we're talking just Pentax here) does not exist in K- or M-edition right? It is only in A-mode.

The thing may be that you did not switch the lens to A-mode. This, combined with the customer menu option to forbid use of aperture ring, may have caused your problem.

Don't know about the 500/4.5

Good luck!

ennacac · 08-30-2008, 07:42 PM

There is not A 500mm 4.5 Pentax lens only the manual version that doesn't stop down automatically since the rear of the lens comes off to allow the use of 49mm filters.

Tom

nixcamic · 08-31-2008, 03:11 PM

Originally Posted by timk

dont forget to select manual focus with the lever

I prefer AF-C for focus confirmation, not sure how the k20d works though.

*Canada_Rockies* · 08-31-2008, 09:35 PM

Originally Posted by nixcamic

I prefer AF-C for focus confirmation, not sure how the k20d works though.

You get focus confirmation in MF mode as well. All three of my Pentax bodies give me confirmation. I tend to use snap-in-focus with my M series lenses at times. Catch the subject as it goes through the focus point automatically if you set the camera to MF.S and hold down the shutter button while keeping the centre focus point on the subject.