Anyone having Zoom infinity problems on istD with old lens?

[don_allison]

I have a great old SMC 70-210 Macro, A series Zoom that I like to use,

especially for macros(1:3 ratio). When I went to use it on the D, I

noticed that zooming at infinity was not focused. The zoom works great

at shorter levels. What gives? Any explanations, svp?

 

Also, I wonder if the lens is stopping down when I have it at A

setting, in AV mode, and have an f stop on the viewer greater than f4

[petre_petrov1]

Don, I don't think that the problem is with the camera. Many Pentax lenses are known to focus "past infinity" (if that makes any logical sense). This is not a "flaw." On the contraray: lenses were specifically designed like that in order to accomodate radical changes in temperature. Hard it is to imagine, your lens--like any other element in the universe--shirnks when the whether is cold, and expands when it's hot. Taking this into account, designers have made "infinity" not a single point on the focus scale, but rather a zone. It means that you will have to be careful when focusing to infinity (rather than just yanking the focus ring to the end), but it also means that you won't be screwed if you happen to shoot in Alaska or Sahara.

[don_allison]

Petr: I don't think I explained the issue well enough. My problem is that I can't get the lens to focus at infinity...it won't go that far. I sense that it might have something with being a full Macro Zoom lens. I may be wrong. The lens works fine otherwise.

[michellemandat]

Don,

I think that the lens had anything wrong in the internal mechanism. The same thing had occur with a mine Nikon lens. It was a screw which was unscrewed and limit the range of focus.

[stemked]

I suddenly had a 100mm f4 macro A do the same thing. It was an issue with the elements in the lens. Have you tried the lens recently on a film camera to see if the problem is only on the *istD?