Third party manual focus lenses on the K7

[vandergus]

A question for all the Pentax gurus here. I've got a friend with a K7 just getting into photography. We were talking a bit about different types of lenses and he said he was interested in trying out some prime lenses but wasn't sure how he felt about giving up the ability to zoom. Knowing that Pentax has really good compatibility with just about any K mount lens, I suggested that he pick up an old manual focus lens to play with and see what he thought without investing a lot of money. I think initially I suggested the SMC-A 50mm f1.7 (for shear value) and the SMC-A 35mm f2 (for a more useful field of view). I recommended SMC-A lenses so he could maintain full metering capabilities instead of having to use stop-down metering with the SMC-M lenses.

Now I recently picked up a Kiron 28mm f2 for my Nikon D40 and it's quite a nice lens. I know they made it in the K mount so I think it would be a good option for my friend as it has a normal field of view, relatively fast aperture, and are pretty cheap if you can find one. What I'm not sure of is how it would function on the K7. Would it be able to use the normal metering modes like SMC-A lenses or would it use stop-down metering like SMC-M lenses?

Also, another related question. I know that with FA and DA lenses, the focus points in the viewfinder light up to indicate focus even when the lens is being focused manually. When using A and M lenses, is this functionality maintained or is focus judged soley by the sharpness of the subject in the viewfinder? I imagine it would be much easier to use the older lenses with that sort of focus confirmation.

Thanks.

[Mr Guy]

It depends on whether the third party lens has an "A" mode on the aperture ring. "M" series and earlier Pentax lenses don't, and thus are relegated to stop down metering. Manual focus lenses also require the use of the center focal point. I'm not entirely sure what the technical reason for that is, but focus and recompose is the normal technique (carried over from film). The focal point indicator for the center point will light with the stock focus screen, as will the green hexagon focus indicator. I mean the stock focus screen, because while the K-7 has a large bright focus screen, even with it, if you're going to do an excessive amount of wide aperture fine focusing with a manual lens, getting a third party screen with aids to manual focus is helpful (ie, split screens, microprisms).

Some helpful reading to pass on: http://www.robertsdonovan.com/?p=1181

[vandergus]

Thanks for the info Mr. Guy. Just what I was looking for. I'll be sure to pass that link along to my friend as I'm sure it'll come in handy when he's hunting for lenses.