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Will
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 01, 2005 - 02:07 pm: | 
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Hi all,
How does one set the focus on a Leica iiia? I usually use the frosted tape trick - but since there is no open back.. How's it done?
Also what would be the best glue to reset the vulcanite back down? It's come loose on both sides of the lens mount - nothing serious, but I want to deal with it before it gets broken off.
Thanks,
Will |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, August 01, 2005 - 04:41 pm: |
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You check the flange to film distance with a precision depth gauge, it should measure 28.80mm.If you do not get this measurement then you have to shim the mount flange until the register is 28.80mm.
The lenses are set up on an optical bench, usually in the form of a specialised jig.
However you can easily duplicate my test jig for screw mount lenses. Get an old Zorki or FED body with a removable back.Bin the back and strip out the shutter and remove the top plate and finder etc. Epoxy a piece of ground glass to the film rails. Shim the register to exactly 28.80mm.
Now you can check the focus of any screw lens in the normal way.If required you can reset the focus scale or alter any internal shims,that a lens may have. In this way you can get the focus of the lens spot on.
I find that the best adhesive for vulcanite that is just loose is Penetrating Cyanoacrylate.This is sold by all good aeromodel shops and is used to tack the balsa framework of flying models together.The adhesive has a very low viscosity and penetrates very small gaps,I use Acetone (CAREFULLY) to remove any excess that finds its way to the exterior.The make I use is called ZAP/CA and is made by Pacer Technology. The bottle comes with a very fine applicator nozzle, but I attach hypodermic needles to the bottle. This allows me to place the adhesive exactly in the right spot.
For pieces of vulcanite that are detached, I use a gap filling cyanoacrylate called ZAP-A-GAP CA+.
There is a product called Prism 4210, this is a Black cyanoacrylate available from Micro tools.It is expensive but does remove the need to paint out the break lines, if the 'white' cyano is visible.
You can use a 1 hour epoxy and mix in a small quantity of matt or semi-matt model enamel to re-attach and fill small gaps.you sculpt the surface of the adhesive in the gap with a cocktail stick as it starts to go off. |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 02, 2005 - 12:34 am: |
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When measuring the flange-to-film distance, keep in mind that the pressure plate rests on the outer film rails. To check the proper distance you have to insert a film and measure from the surface of the film to the lens mount flange. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 02, 2005 - 12:41 pm: |
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Does the 111a have separate film rail and pressure plate rail dimensions? I have just measured mine and get 28.80mm with or without film.In all my reference literature the Leica screw M39x26tpi has a register of 28.80mm,there is no reference to a pressure plate rail dimension.
You can get in quite a mess when setting up the Leica M series if you do not use the correct measurement reference point.In the M series the film and pressure plate rails do have different dimensions.
Whilst on the subject of LTM registers I wonder if anybody can answer this query.
I have made a number of adapters to mount M42 lenses on various M39 Leica and Zorki/FED specials.All my adapters have a stand off of 16.66mm-M42 register is 45.46mm,M39 register is 28.80mm; therefore 45.46-28.80=16.66mm.The adapter has to increase the register of the camera by 16.66mm to allow the M42 lens to focus to infinity.I mount 24mm and shorter wide-angles on the adapters and the focus is spot on for all the lenses thus so-far mounted, wide angle lenses are more dependant on correct dimensions than longer lenses.
All the Leica screw to M42 adapters coming out of China and the Far East have a 'Stand off' measurement of 16.00mm.Anybody know why? One advert states that the adapter allows the mounting of M42 lenses on the M series, via the Leica screw to bayonet adapter.Not having a Leica screw to bayonet adapter I cannot check if this combination of adapters gives the correct M42 register. |
Will
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 02, 2005 - 07:45 pm: |
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Thanks Glenn, Winfried. Any more clarity on the rail dimensions? My camera seems to confirm what Winfried writes. I come up with the 28.8mm with a piece of film laid on top of the pressure plate. Without it the measurement is greater. Could there be different rails with respect to build date? I guess I could take the camera apart to check, but I just put it back together! Again thanks for all the help thus far.
Will |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 03, 2005 - 08:11 am: |
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Will,
Just taken mine apart,it seems that it has been played about with-signs of very funny machining/stoning marks on rails.It is the only screw Leica I have,it was purchased as being built up from parts and as it always works,I did not give it much thought.
Winfried is correct in his statement,it should have got the warning bells ringing sooner.I always set my Zorki/FED specials up from a piece of inserted film.Do not know why I thought my 111a should be different or more importantly why the rails have been got at! |
Will
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 03, 2005 - 06:23 pm: |
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Glenn, Thanks - I didn't mean to put you through that! But it is greatly appreciated. Again thanks for all the help.
Will |
