Jena Tessar 5cm 3.5 Exakta Help

[stonedes]

Hello,

Does anyone know of info on cleaning/disassembling this old lens? Serial # 3065310 dates from the late 40s I would guess. Does have the red T and is the metered non-export version.

I've never cleaned a lens and want to learn. This seems like a good one to practice on because its quite tiny and hopefully relatively simple to take apart.

Any help appreciated. Thanks!

[Attila]

Buy a common lens and learn on that , not start to learn on a rarity...
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[stonedes]

Thanks for the advice Atilla. However I was thinking since I only paid $20 and I believe this only has 4 elements it makes sense. I know its old, but really wouldn't this lens be easy to disassemble?

[Attila]

[inombrable]

Attila is right, my first two lenses (attempts really) were 2 tessars, they ended up in the bin. After that i have fixed several of those but yes is better to practice on something more "common". once i bougth a job lot of lenses for 4.5 dollars so you might want to look for something like that and practice a lot.

[Jesito]

I would suggest to get a Domiplan on Exakta mount to try first.
Even if it ends in the bin, it won't be too much loss

An old Tessar is a respectable lens, better try to keep it for a later try.

Regards.
Jes.
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[stonedes]

Thanks everyone, I'll see if I can find a piece of junk to work on. Since I'm in California, It'll probably be something Japanese or Korean. Are there any good references online for cleaning lenses?

[SXR_Mark]

To do the job properly, you will need to invest far more than the cost of this lens in some decent tools.

A top quality set of precision screwdrivers is essential. Get ones with good handles that you can grip securely. The ones with thin metal handles are too hard to hold firmly and you are much more likely to damage a screw head if you can't apply enough pressure. You will need flat and cross type screwdrivers. Most lenses have tiny grub screws that require a flat tip of 0.7 mm or so width. Sizes ranging up to say 3mm will also be needed. For cross head screws I use PH00 and PH0, but you need to be careful as Japanese lenses actually use JIS screws that are unique to the Japanese industry. It is easy to "cam out" when trying to undo a stubborn screw and damage the head. Use drops of iso-propyl alcohol (IPA, propan-2-ol) to lubricate and loosen stubborn screws.

You MUST also buy a good lens wrench (aka lens spanner) to undo the rings that hold the glass elements in place. There are two basic types, flat bladed and point-tipped. Eventually you will need both. These are often available on ebay.

To clean the glass, wear surgical type gloves and use good micro-fibre clothes designed for cleaning lenses. (Disposable lens tissues are better but ultimately rather expensive). Always handle the cloth with gloves or you will cover it in grease from your hands that will then leave smears on the glass. Never use common paper tissues as they scratch the coatings. Keep one cloth for a first cleaning and another or the final clean. Transfer of grease from cloth to lens is a big problem.

I use a range of cleaning agents. At the moment, my preferred all-round cleaner is Sticklers fibre optic and splice cleaner. This dries quickly and dissipates static quite well.

http://www.sticklerscleaners.com/products/cleaning-fluids.aspx

I also use pure methanol and ROR (Residual Oil Remover). Some solvents work better on some coatings than others. I like the Sticklers as it doesn't dissolve the black paint that is applied to the edge of some lenses.

After solvent cleaning, there will always be a bit of dust that gets picked by static attraction. Use a good air blower (eg Giottos Rocket Blower) to shift this if possible. Inevitably, you will find a little very fine dust which cannot be removed as it is too well stuck by static. Unless you have a proper clean room, you will have to live with this.

I have yet to find the "perfect" technique for cleaning lens elements. What works well for some doesn't work on others. Sometimes I put the fluid on the cloth, and sometimes on the glass. In general, you want to wipe the glass with a single stroke that removes all the grime and leaves behind just a thin film of solvent that evaporates instantly without leaving any residue. Too much fluid will leave a spot on the lens as it dries. It is all too easy to leave grease smears on the lens as well. Don't apply too much pressure or you will scratch the coatings. Too much cleaning will make the glass cold (loss of latent heat required for the solvents to evaporate) and this can result in moisture condensing on the glass making it impossible to wipe without smearing. This is a particular problem if you use methanol as it is never perfectly dry and you can get droplets condensing out of the solvent onto the glass. Excessive rubbing can also build up the static charge that makes dust impossible to remove - I work over an anti-static mat used for electronics assembly.

Inspect the glass carefully with an LED touch shining both onto and through the glass. LED torches are very god at showing up blemishes in lenses. Angle the glass and light source to ensure any smears show up well. Often, smears can only be seen clearly when the lens is reassembled. Old coatings have often deteriorated naturally and will scatter the torch light showing up a myriad of tiny points of light. There is nothing you can do about this. You need to recognise when the coating is damaged and that its not dust that is causing the scatter.

Inevitably, you will need to learn through experience. As others have said, buy a cheap lens to practice on - but don't get a zoom as the are mechanically very complicated.
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[stonedes]

Spectacular reply SRX! Just what I wanted and also further emphasizes that's there's more to cleaning a lens that you would first imagine. I'm really looking forward to digging in as I also have an SMC Tak 50 that is showing signs of fungus.

Thanks again to everyone!

[JohnBar]

I would advocate the use of chamois leather for lens cleaning, also if you need a clean room try this:

In the bathroom take a hot shower for ten minutes, then open windows to regain normal humidity. This has the effect of making airborne dust sink to the floor, long enough to perform lens cleaning.
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