Topic: stiff focussing...

[Chalky]

hi all,
Apologies for what is no doubt an amatuer question.

Today I received my new 50mm lens for my practika BC1. The lens seems fine, very clean and aperature ring moves smoothly. However, when focussing, it is extremely stiff. It's smooth and doesn't feel like there is anything catching, it is just really tight, which makes focussing slower than I'd like.

Is this a common lens problem? and is there anything I can do to loosen it up without causing any damage?

thank you all,
Matt

 

[Francois]

The grease on the helix is probably dried up.

I've never really worked on a lens without wrecking the thing...

Depending on the way it's made, sometimes they have a single screw on the focus ring which engages with a slot inside. Once you remove this one, you have access to the helix for re-greasing. Molybdenum grease is used there.

As usual, try to remove the fewest parts. And if it won't budge it usually means you're doing it wrong.

[Pete_R]

Francois is right about the thick grease. But, unless you're prepared to lose the lens, it isn't something I'd recommend you try doing yourself. Splitting helicals has lots of potential pitfalls. The lens probably isn't worth paying someone else to do it so it may be a case of living with it or finding another.

[Chalky]

Thanks both. Yeah I don't trust myself to work on it without ruining it! I'll put a roll through it and see how I get on. Cheers.

[Alan]

yea i worked on an old Canon FD lens with the same problem, took it apart
"serviced" it and put it back together but i couldnt focus to infinity.

its still sitting in the drawer 

it all seemed so simple at the time, but yea those helicals are tricky.

if they can be picked up cheap, get another and experiment with the
stiff one !

[LChanyungco]

im not sure if the helical is exposed on this lens but if it is you could work a small dab of super thin oil like rem oil, militec, or sewing machine oil into the threads. add a toothpick tip sized amount and turn the focus ring from closest focus to infinity over and over until the oil penetrates the old lube. i did this with an old leitz lens and it worked nicely

[Terry]

Can you post a photo or two?

[LChanyungco]

me or chalky ?

Can you post a photo or two?

[Nigel]

I've got the similar issue with a 35mm Zuiko lens, I did think about trying the dab of oil but I'm concerned it'll work it's way on to one of the elements. 

[LChanyungco]

too much oil and it'll seep around for sure. but if you use a toothpick to wipe a tiny bit on the helical you'll be ok. at your own risk of course

[Terry]

Re the photo--I was asking Chalky.  Maybe we could get an idea what sort of mechanism the lens uses.  I've disassembled and CLA'd a few and found that some are really quite simple if you're careful and you document things (like making realignment marks on the helicals!)

[DS]

making realignment marks on the helicals!

This is key- but otherwise I agree that it's all fairly straightfoward if you take your time.

[Pete_R]

A while back I documented the dismantling of a Zeiss 50mm f/1.7. It won't be the same but it might give an idea as to what's involved in doing a job like this. You can find it at http://www.monopix.co.uk/zeiss50mm.shtml

[Chalky]

Hi all,
Thanks for all the comments.

I'll post some pics if I can (don't have a digi cam other than my phone so not so easy!).

Have to admit I'm not too confident to dismantle and rebuild based on previous experience! But I will have a look at the link Peter posted below.

It has actually loosened up a little, I've just been twisting the focus from infinity to close and back again, so it may have just been stiff from lack of use.

Cheers all 

Matt

[sethasaurus]

A lens isn't so daunting if you're methodical and take your time.

A couple of index marks (with a permanent marker or a scriber) will help you line things up again.

Basically, if it has a double helix, you can only be half a turn wrong. If it's a triple, then you might find you're a third of a turn one way or the other. You'll only have to wind it out, realign and wind it back in.
Count the number of turns as you undo anything important like a lens element from a thread. If you wind it back in the same number of turns, you can't really go wrong.

The most common problem people have is forgetting (where, what? which screw goes where?) so.. don't forget!
If you have a camera on your cellphone that can do fairly good close-ups, you can take out a screw and lay it on the table next to where it came from and snap a pic.

What else..? Try and use the right tool for the job (e.g.Don't use a screwdriver as a lever).

Also - patience, and don't force anything! If a screw doesn't want to budge and it isn't making sense, don't forget that some manufacturers will sneak the odd lefty in there (see if you can turn it clockwise to undo it).
Not sure if you'll find any in your lens, but it's a trick to look out for.

That's my 2c 

[Nigel]

These are all great tips thank you guys. I'm still not sure I'm ready to give it a go. I might see if I can pick up some old lens at a boot sale, or something, to practice on.