Infinity focusing

I think that's the right terminology.I was speaking to one of the guys in Ffordes photography the other day whilst i was purchasing a new tripod (grabbed a rather good deal as well i may add) .I have two manual focusing lenses at present ,my problem is,getting them to focus to any great distance ,great close up ,but anything distant they wont,the chap at |Ffordes said the cameras custom settings may be needing tweaked .Has anyone come across this problem .Said camera is the Pentax K100D sr .Any input would be greatly appreciated ;


regards Sean

Two questions:

1) Are your manual lenses screw-mount? If yes, then
2) Is the screw-to-K bayonet adaptor flush with the lens flange?

If the adaptor is protruding ever so slightly it will most likely prevent focusing to infinity.

Just my 2p worth...

Th pentax 50mm prime f2 is k mount, the cosina is 200mm prime m42 screw mount,both have the same prob

Do you have any other lenses that don't suffer from this? If so, I would say it's a problem with the lenses, rather then the camera.

I'm wondering if you got these lenses secondhand, from the same person, who may have taken them apart and reassembled them incorrectly...

Dan

When I fixed my SMC-FA 80-320 (which is autofocus BTW) I had to calibrate it to achieve infinity focus.
Most lenses have an adjustment somewhere that provides for infinity focus.

However, that said, some lenses were not designed for infinity. The SMC-FA 85/1.4 is, I believe, one such lens - designed specifically for portraiture it doesn't stand up too well for infinity.

The other question is - do you have any Pentax autofocus lenses (like the kit lens)? Can you check the infinity focus with them?

There's nothing you can adjust yourself on the camera that will fix this. It's most likely a lens problem. However, there's a very slim chance that the CCD on the camera has been adjusted incorrectly, making the camera slightly myopic. A visit to a Pentax service centre could sort that out...
(But check the kit lens first )

Matt

The first thing to check is the dioptre adjustment on the viewfinder. Point the camera at a blank area (wall or sky) and adjust until the etched guide lines are sharpest. You don't need to focus the lens to do this and it's probably better defocused. This ensures you are seeing the image sharply on the ground glass.

There is so much DOF at long distances that a 50mm lens that won't focus on infinity is very unusual Also that another lens won't either really points away from the lenses being a problem. Try the above first and see what happens.