OpticalFlow wrote:
When you had it open, did you see a straightforward way to fine-tune the infinity stop ?
No, I have not found a straightforward way to fine-tune infinity, but there is a very easy way to mess up infinity altogether. If someone has tampered with the rubber ring as you pointed out, there's a good chance he has removed the front lens group (not that hard to do) for cleaning or whatever other reason, and since those threads have multiple starts (because the pitch has to be steep), you can put it back together in several ways - but only one of them is th right way, and if you haven't marked that one just before taking it apart, finding the right position is an exercise in patience. Luckily I had my first encounter with that kind of problem before taking this lens apart, so I kind of knew what I was getting into.
Apart from this, I haven't found a way to change the infinity setting, and I don't really see a viable way how from looking at how the lens works. During focusing, the rear lens groups are stationary, and only the front group moves. Changing the position of the rotary stop of the front group would change the relative position of the front group to the rest of the optical system. This can't possibly be a good thing with a properly adjusted lens.
Another thing that is worth noting is that with lens, you also get a problem if the adapter is too short. I've read someone claim here that the lens is not parfocal (same focus for all zoom setting), something I have not found to be the case with my Leitaxed-for-Nikon copy on a Nikon (Fuji) body. You could accurately focus at 70mm, then zoom out to 35mm, stop down and take the shot.
Now that I have moved to NEX, I know where that statement came from, because an adapter that is too short will throw off the focus at the short end of the zoom range, massively. Let's say you have to set the scale to something between 15m and infinity to actuallay focus to infinity at 70mm, and you may have to change the scale to 5m when fosussing to infinity at the 35mm setting. Very annoying to have to refocus after zooming, so the adapter has to be exactly right. Not that hard to do with today's manufacturing technology, but it seems that all this crying about not being able to reach infinity has led to the opposite extreme, manufacturers wanting to be "on the safe side" even with badly adjusted leses. Well, that's fine with lenses that move as a whole group for focusing (like your Planar), but it is a big problem for zooms.
I've sent back my last adapter because of this problem (it was 0.4mm too short, for F's sake, that's huge and cannot be excused with any modern-era manufacturing tolerances!) and the seller wouldn't even acknowlede that there was a problem.
If you do get close to infinity focus then the front lens group has been fitted correctly! Only if you focus way off infinity and get much higher magnification than 1:2.5 in macro mode do you need to do this disassembly.
I would try different adapters.
For what it's worth, it could be that your 50/1.7 just happens to have a very generous infinity margin, and that's why your adapter works with that lens, but not the 35-70.
dcjs wrote:
I've sent back my last adapter because of this problem (it was 0.4mm too short, for F's sake, that's huge and cannot be excused with any modern-era manufacturing tolerances!) and the seller wouldn't even acknowlede that there was a problem.
Interesting. I've bought a C/Y adapter from big_is some time ago and it's too thick: not getting infinity with my Planar 50/1.4. It's even difficult to mount (too much friction).
Thanks for your suggestions, dcjs, jotdeh and AhamB.
I can focus quite close to infinity, say maybe 30~40m (my guess without measuring, now its dark), and I definitely can't focus past infinity. I agree with jotdeh that it is unlikely that the front part isn't in the wrong thread - it would be off a lot more in that case.
So if it is the adapter, my current adapter is slightly too thick. However, If it is too thick I shouldn't be able to focus the Planar 50/1.7 to infinity unless the Planar's infinity stop is misaligned. The Planar looks like it has never been opened so it appears less likely that the infinity setting has been misaligned - in contrast to the 35-70 which shows clear signs of having been opened before. Jotdeh, I'm not quite sure what you mean with a "generous infinity margin" w.r.t. to the Planar 50/1.7.
I wanted to buy a Leitax mount for the 35-70 anyway as the adapter has a bit of rotational play which I find very annoying. So, maybe I'll just do that and hope it'll fix the issue. If not I might send it in to a professional repair place to have it infinity-adjusted. I'm tempted to try DIY as I have opened a lot of lenses and played around with them, but somehow I don't quite dare to open this one without a clear plan of how to approach the task.
OpticalFlow wrote:
Jotdeh, I'm not quite sure what you mean with a "generous infinity margin" w.r.t. to the Planar 50/1.7.
I meant that possibly the 1.7 happens to be at the tolerance limit allowed by Zeiss (or slipped QC) so that - on a nominal mount - it would focus past infinity. So if your adapter is too thick (which we don't know for sure until you easure it) then you might be lucky with just this lens.
If you really want to adjust the infinity stop of the lens (not recommended as explained by dcjs) then the only way I can think of is to remove the small plate that is held by two screws (see pic on previous page) and shortening it, then reassemble. I would personally not do this. Try your luck with at least one more adapter, maybe the Leitax!
