Originally posted by desertscape Not true.
Again, not true.
I don't know. I was told by a vendor that there is an interaction between the lens and a body. In fact I did read in the manual that close focus issues are fixed by adjust 3 mirror screws in the body. My own tests indicate a lack of focus for objects 2m away, for example. Not a big deal. I don't need close focus, only infinity.
Bought the lens on Ebay and seems in near perfect shape. Flat frames look great, after some cleaning.
However if no sharp focus at infinity, it's useless to me. I can get a refund from Ebay, if I do it pretty soon. Of course, this is all academic without stars to test on. Clouds and more clouds.
---------- Post added 08-01-15 at 11:20 PM ----------
Originally posted by 672 Having shot this lens on a 645D and Z and Canon full frame, my experience is that it pretty much will not be very focused at f4. Maybe on film , but not on digital.
I'll be using a Nikon APC sensor. That may help. What f/stop did you find a sharp focus at? I'm reluctant to use the iris, but could cut a mask for it.
---------- Post added 08-01-15 at 11:23 PM ----------
Originally posted by pentaxus If your adapter provides the correct flange to sensor distance, and you turn the focusing ring so that the infinity mark is at the indicator (the focusing ring stops there) astro photos should be in focus on your Nikon. I'm not sure what you mean by "default focus". You should be able to check focus with your camera by focusing on things that are far away (a kilometer or more). Focus can be adjusted, but if the adapter is properly made you shouldn't need to do anything.
There is a difference between the focus of something "far away" and a point source hundreds of light years away. My capture software will measure FWHM in real time. It only takes a very tiny error to be obvious in an astro photo. Hence my concern.