Stiff focusing on slr lenses

dpurdy · Feb 27, 2009

I recently beefed up my Pentax 67 lens collection so now I have 3 of the newer variety and 3 of the older all metal type. The newer ones (55,135,165) all focus very easily with little effort. Of the older ones (75,90,105) the 75 and 90 take more effort to focus than the 105 which is as easy as the newer ones. The 75 and 90 seem stiffer to turn but very smooth with no sense of grit or anything.

I am wondering why the 105 which is just as old as the other two is so much easier to focus. It is buttery smooth and very easy to turn. I am wondering if the other lenses actually need a CLA, or do I just need to sit in front of a movie on TV and work them till they get easier. Or if I just work them will they actually get stiffer rather than easier.

There isn't a Pentax repair person in the area I would trust to give me any answer except "you definitely need to bring it in for a CLA".

Thanks
Dennis

John Koehrer · Feb 27, 2009

Usually it's old lube. It's possible that the more freely focusing lenses were CLA'd at one time.

Nick Zentena · Feb 27, 2009

Or maybe just used more recently? I've bought older lenses that were stiff to begin with. After some use the lube got going and they were okay.

archphoto · Feb 27, 2009

The same here.
Q: how much did you use the 75 and 90 lately ?
Try to loosen them up and if they remain too stiff for you send them out for a CLA.
Basicly any good repairman can do this job, they are not that compicated to service.
(I have owned a Pentax 6x7)
Using them in this way will not harm the lens unless they are realy way too stiff.

Peter

dpurdy · Feb 27, 2009

archphoto said:
The same here.
Q: how much did you use the 75 and 90 lately ?
Try to loosen them up and if they remain too stiff for you send them out for a CLA.
Basicly any good repairman can do this job, they are not that compicated to service.
(I have owned a Pentax 6x7)
Using them in this way will not harm the lens unless they are realy way too stiff.

Peter

I just got the 75 off ebay in seemingly unused condition. The 90 I have had for several years and it has always been stiff, especially in cold weather. I can't really afford lens CLAs but if it gets worse maybe. If a repairman can get in and lube the lens, is it possible for a layman?
Dennis

David A. Goldfarb · Feb 27, 2009

Does Pentax offer a quick focus lever? I find it indispensable on my Bronica S2a, and I know Hasselblad also makes one.

archphoto · Feb 27, 2009

I don't have the Pentax 6x7 and lenses anymore..... otherwise I could give you instructions about it.
You will need: the propper size Philips screwdrivers (small) and the propper grease and patience.

For grease I use a lythium based grease such as Mobil Grease 28 or Mobilith SHC 460.
Both are known in aircraft maintenance and have ultra low gassing and high melting points.
Maybe you could use Yamaha lithium chain grease used for motorbikes, but I have never tested it.

The 75 should be rather easy to do, the 90 is the shutter-lens, isn't ?!
The thing is: you will have to take the lens apart, photographing each step of the way and than re-assemble after
washing out and re-greasing. this re-greasing should be done with not too much grease, just cover it, it need
not to "swimm" in the grease.

If you have an old lens (35mm lens or so) try it on that one first so you get the feel for it.

Give me a PM if you want to do it, so we can exchange email adresses and I can guid you through it.

Peter

archphoto · Feb 27, 2009

Yes David it does, still got one in Holland I believe.....

Mmmmmm. nice for my new RB gear if it fits....

John Koehrer · Feb 28, 2009

Dennis, It's not a difficult process but Reassembly can be challenging if you take the helical apart. There are 6 or 8 threads in the helical which means you have more than one choice to make a mistake. And you will.
If you're not on the correct thread you won't be able to focus on infinity or line up the indexing blade or stop down linkages.
Save your money & fix one at a time.

dpurdy · Feb 28, 2009

Yes I think that is the advice I will follow after pondering the lenses for awhile with screw driver in hand I thought... nah.
David yes pentax does offer one of those quick focus things you put around the lens. I have never tried one. I will check ebay and see how valuable they are.

Thanks
Dennis

Oh also the 75 did seem to get easier after cranking it back and forth for several minutes.

Stiff focusing on slr lenses

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