I missed my 35-70 quite a bit so I got an almost new one... which I dropped within a matter of days.
It's hard to believe, but it looks like I was lucky enough and overall the IQ has not suffered. However, focussing is very stiff now - the focus barrel rubs against the zoom barrel at the dent.
So my plan is to remove the focus barrel, file away some of the material and reassemble.
Exactly how do I take the lens apart, as little as required? I don't want to end up with an impossible puzzle of parts...
Ooooh, bummer. Sorry about that. Seems like Jae (Flypenfly) has a CY35-70 that he needs to assemble. Maybe you guys can work together - and post some pics for those of us who might need them in the future.
Yes, I'm really annoyed with this... I should never buy "new" lenses anyway, as it keeps me from using them. But the dent is like the first stain of tomato sauce on a new shirt. After it's happened I can enjoy the rest of the meal much better
A few months ago, I took photos and wrote up a description to sell my CZ 35-70/3.4 it on the auction site. It has a jaggedy mark on its front element coating. Not a scratch, a mark. Then I recanted. It still takes great photos, yet its resale value is compromised.
Have you considered sliding a small, flat-bladed screwdriver in, and carefully wiggling, torquing, and/or prying it - just a bit? You could even put a layer of some thin yet resilient polymer sheet under the driver bit, to protect the lens barrel beneath.
OTOH, taking it apart could be a most-excellent adventure. Please, keep us posted.
Jim, yes, that's my experience too - if an item is not mint looking enough to fetch the price the IQ would warrant, it's best kept as a 'user'.
I had tried to use a screwdrive before, but didn't feel comfortable with it. Now I used some 240 grit sandpaper, slid in inbetween the gap and rotated the focus barrel. It's still stiffer than I'd like, but definitely usable!
I think sandpaper isn't a great idea because you'll probably get grains from the sandpaper and/or metal particles from the zoom/focus ring in the focusing helicoid or other parts of the mechanism (or between the optics).
Yes I was afraid of that as well, it creates very fine dust. I tried my best working very slowly, holding the lens with the opening to the bottom to let the dust fall out.
Maybe wetting the sandpaper a bit is a good idea to bind the dust?
it LOOKS like you do NOT need to disassemble it. And fileing on that surface would be a huge mistake.
Instead try to reform the circularity by putting it in a rubber jawed vice and squeezing it on it's (now) long diameter. Monitor the gaps on the sides so you don't squeeze the inner barrel, and squeeze it one neat the section with the ding, and you should be OK.
I dunno... that sounds so much better than using a file (or sandpaper!!) on it.
I think the problem is that such small deformation (fraction of a mm compared to 60 mm barrel) it will just spring back. Still worth a try, thanks Bif!
Well, you're looking at it so you know best. If it's a dimple, dent, or small depression then my idea will only help a little bit (enough? you can probably guess yourself by looking at it). If the deformation is more of a gentle slope it should work the treat tho. In the image it looks like a gentle enough slope that it should work. While in the vice under some pressure and if that alone doesn't do the trick then I would tap on it at the same time with a rubber mallet - gently but enough.
If neither way worked then disassemble it and use some soft wood and a hammer/mallet to pound out the dent. That would actually be the most professional way to go about it - but also the most work too. :-/
Well you are right, the oval shape is very slight, and as long as I focus holding the lens in two points then the focus is pretty smooth! I need to get myself access to a vice and see what I can do with that - sounds a bit scary though
Just a quick update - I've finally dared to take the lens apart (three components - front assembly, focussing cylinder and rear assembly). First thing I tried again was to sand away the bump on the inside caused by the dent. It didn't solve the focussing issue (still way too stiff, depending where I pinch the lens with two fingers).
So then I went Bif's way, though sans vice. I gently "massaged" the cylinder into shape a couple of times, and now...
well it's not a "brand-new" feeling, but definitely very useable!
I'm happy! I'll post a pic or two later for those interested.
Thanks If there's dust in your lens I'd give this a try without hesitation now. You might be lucky and it's on the surfaces exposed by this disassembly (not unlikely, since the zoom and focussing action is happening here). Only getting to the aperture would be a bit more adventurous.
No offense but it doesn't look sharp to me? It looks ever so slightly off, not that crisp punch of sharpness that a Zeiss lens provides.
I'd also try shooting the side of a semi truck trailer that has graphics on it to test it for edge to edge alignment of focusing at the film plane. That dent looks like a bad place to hit a lens.
I'd actually say there is a good amount of pop, but let's not get into that here
However I really do think (want to believe? lol!) that the lens is fine.
In fact this may have been the best spot to hit the lens. No lens elements are directly attached to the one touch barrel (let's call it that), and it could be restored just by working this part.
I'll do a more controlled "wall test" in the next few days, just to make sure. It's quite possible that the plane of focus is in ever so slightly in front (i.e. on top) of the rock at the bottom.
Hope it winds up being stellar, and thanks for the info on no elements behind the impact area...that is a good thing you're right. I was thinking any impact in the barrel would blunt trauma it's way to wiggling an element, but I think these lenses are tougher than I think since they're held in place by the force of curved metal as well...the science is interesting, and typical me...not something I'm as educated on as I'd like.
I've had a C/Y 35-70 for about a year now. It never quite focused to infinity on my 5D which I blamed on the cheapo adapter and my plan was to fix that by using a Leitax. Now I've also picked up a Planar 50/1.7 and well - it turns out that the cheapo adapter gives perfect infinity with the Planar. My C/Y 35-70 has some signs of previous work (rubber grip taken off and glued back on) so that I now suspect that it was not adjusted properly in the first place (too late to complain to the ebay seller now).
When you had it open, did you see a straightforward way to fine-tune the infinity stop ?
