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Post by genazzano on May 19, 2013 16:24:03 GMT -5
I actually found an Exakta mount lens that matches the Finetta lens. It's at www.liveauctioneers.com/item/1218326 and it is described as "J.L. France, 'Telec 4,5/90', Nr. 4207" with the period after the "L". Curiously the lens looks exactly like a black painted version of the 27mm Finetta lens except it's attached to an Exakta adapter. Personally, screwing the 90mm lens made for a Finetta into a simple Exakta adapter doesn't fully qualify as having produced an Exakta lens, just a painted Finetta lens and an adapter. Hmmm, the mystery deepens.
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Post by genazzano on May 19, 2013 15:53:46 GMT -5
There are many errors repeated again and again on the web regarding this lens. Captain Jack uses "J.L. Telec, France" whereas many others use "J.L. France" with the period after the "L". Both would appear to be wrong and Capt. Jack's would be a bit too creative but who knows?
The Lens is marked "J.L France F=90 1:4.5 TELEC N°3239". So given the conventions of labeling lenses, the most likely name would be TELEC... or not. I wish I could find a real lens with the Exakta mount to which Capt. Jack refers to see if that lens is actually labeled "J.L.Telec".
In any event, the company is clearly "lesser known".
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Post by genazzano on May 19, 2013 14:37:44 GMT -5
You're right, of course. I just considered the "C" as the first model with or without the switch. When I pulled the camera apart I noted that the front cast plate has the opening and mount boss for the switch though they are not used.
I gave up considering a switched type since prices are now stratospheric, anyway. Ciao! David
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Post by genazzano on May 19, 2013 3:30:24 GMT -5
I just finished cleaning up my Finetta Super which came with an immaculate 45mm f/2.8 Finetar and a 90mm f/4.5 Telec from J.L.France. Does anyone have any information on the Telec lens and background on J.L.France? I'm preparing a page on the Finetta and the J.L.France lens but there is little info available on the latter by running a simple Google search.
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Post by genazzano on May 19, 2013 2:49:14 GMT -5
Thanks, very much.
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Post by genazzano on May 18, 2013 13:46:14 GMT -5
I now understand what patients go through. Hope she did well. I started 9 months ago and it's been a looong 9 months but it has been worth everything. I'll probably be out of action for a week or so. I expect to be finished (poor choice of words, maybe) in a month or so. Thanks for the helpful kind wishes. Yes the Argus is a C with uncoupled RF. I have 2 now. This new one needed a lot of work including a new RF mirror, new viewfinder lenses and new leatherette from Cameraleaather. Here's one that I did a couple years ago (#7397).
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Post by genazzano on May 18, 2013 2:06:02 GMT -5
It's a beautiful morning and there is a break in the incessant chemo for a while and I look forward to reading new and old posts here as well as to getting back to my Argus C restoration and my new Finetta IV. I'd like to dig up new info on the J.L. France lens and shoot a roll in my Heligon Karat 36. Life is good. Ciao! David
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Post by genazzano on May 13, 2013 2:06:45 GMT -5
Can't think of a better place to discuss mold than over a pint or two.
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Post by genazzano on May 12, 2013 13:49:15 GMT -5
Complimenti!
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Post by genazzano on May 12, 2013 13:42:30 GMT -5
That's encouraging. I'm a mammalian cell biologist and don't know jack about mold except that it's a pain. We used fungizone, i.e. Amphotericin-B, to keep common mold from growing out in cell culture medium before the advent of effective clean hoods. We all have read endless opinions on fungal growth on lenses but not much regarding what kind of mold is responsible. To etch glass it would have to produce some impressive stuff, presumably strong acids. You're right about the source which is probably common airborne spores and sterilization of lenses would be an exercise in futility. Thanks for the telling about your experiences after the lenses have been cleaned.
David
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Post by genazzano on May 12, 2013 3:06:18 GMT -5
I guess I've been lucky not having run into serious mold problems until now. Just got a Perfex 33 and the lens is moldy.... really moldy. I will be discarding it and search for a cleaner one.
My question is does anyone have experience in having the mold return after a cleaning? Unless extraordinaryly thorough sterilization is done, and it rarely is, the mold spores remain in the lens housing and mounts. So, I would expect that the mold would return at some time.
David
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Post by genazzano on Apr 17, 2013 9:27:48 GMT -5
I always like to see how close I can come before Stephen arrives with the right answers. My compliments on all the help you give.
Ciao! David
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Post by genazzano on Apr 17, 2013 5:02:38 GMT -5
What I did was down and dirty... just to get a good image from a lens that was not standard for a body. In my case, it was a 1938 B&L 75mm telephoto lens for the Argus C2-C3.
If you are inclined then shimming the focusing unit and collimation should be done. Or give it to a repair person who will then likely use a jig that replicates the necessary parameters for the lens and normally end up with the lens that works on any body. Of course you can discard all of this and mount the lens on an SLR and actually see the focused image but it is likely that the lens will not properly focus at infinity with the lens wide open.
Mathematically, you have three parameters, lens position at close distance, at infinity, and the function defined by the helicals which determine the rate of change internally among lens groups with regard to rotation of the helicals. Obviously, the function defined by the gears in the helicals is fixed and cannot be adjusted. Also, the situation is simple if only two lens groups move as you rotate the focusing ring, and unbearably complicated when multiple groups move at different rates such as in zoom lenses that require maintenance of focus throughout the focusing range for all magnifications. I'm too old to do that anymore. I must also warn you that although I designed optical systems, my students were the ones that could actually make them work.
Check the focus of the lens on an SLR throughout the distance range. If the lens remains sharp, then you're fortunate since collimation can be done with shims.
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Post by genazzano on Apr 17, 2013 3:37:10 GMT -5
My 2 cents: Discard both old and new lens liquid cleaners and use freshly prepared solutions using dilute mild detergents that do not contain ammonia or alkaline pH's and a bit of ethanol. As mentioned above, the old cleaners can chemically change with time. I normally limit cleaning to use of soft absolutely clean brushes (the cosmetic counter at the store is a great source of very soft and effective lens brushes). You can check the pH of a cleaning solution using pH paper strips normally sold for swimming pools. The pH range best for lenses is about neutral, i.e. 6.8 - 7.1. I think excellent lens cleaning solutions are sold by Hoya and often at optometrist stores.
Also, remember that purified water and alcohols will evaporate but cleaners leave residue. So never use cleaners in a way that will permit the solution to be drawn into the lens retainers by capillary action and on into the interior of your lens.... OK, I'll shut up now. Ciao! David
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Post by genazzano on Apr 17, 2013 3:20:27 GMT -5
I had a problem with similar camera: The focus was accurate at the closest distance but that fell off as the target moved further out from the camera to infinity. The focus of rangefinders is not optical as it is in SLR's, but rather dependent on the accurate machining of the helicals and a careful calibration of lens elements. In some, often the Russian long lenses, the rate that the helicals move the lens elements from close focus to infinity does not match the change in the real focus of the lens.
I set up my camera on a tripod and added a reliable rangefinder attachment to give accurate distances. I then opened the diaphragm to maximum to minimize the dof at all distances and taped a simple ground glass to the film plane (I actually use a fiber optic faceplate mounted against the film plane which is more accurate than a ground glass plate if such accuracy is needed). I then focused the closest image possible with the lens, in your case 2.5m, marked the real distance given by the accessory RF, and recorded the distance reading that appeared on the lens. I then repeated this using targets at 5 or so different distances from the film plane. This gave me a "real" vs "lens indicated distance". The two numbers ideally should always be the same, but they are often different such as in your case with the Jupiter. You can actually plot the real distance on a X axis, versus the "apparent distance" on the Y axis as indicated on the lens. You can then see graphically how the real vs indicated distances fall off as you approach infinity.
It appears that the Jupiter 11 was set up calibrating the closest distance but the rate of lens movement through out to infinity was not calibrated. On some lenses you can recalibrate the lens so that the closest point can be maintained and the indicated infinity point brought back into agreement with the real distance. However, this is not practical in the Jupiter 11 without dismantling the lens and shimming the right lens group. What I did was more basic and just as accurate in the final analysis: Using a piece of silver mylar tape (used for automobile trimming), I re-labeled the distance scale on the lens so that it agreed with the real distance as measured by the accessory rf.
It really isn't important whether the distance scale on the Russian lens be accurate. It is only important that you know where the real focus is located at 5 or 6 points between close (2.5m) and infinity. In my case, the lens did not focus accurately at infinity but was fairly accurate at all other distances. This is usually not a problem since you need only stop down at long distances to create a dof that brings distant targets sufficiently into focus. It's better to do this than at close distances where the dof is comparatively smaller.
At least 2 of my Russian lenses ended up in the bin due to the poor images as well as inaccurate distance calibration. Also, once you have re-calibrated the lens, the coupled internal rangefinder is no longer useful and an accessory rf is used.
Of course, you can always shoot stopped down to give yourself a good dof and the images may be fine (e.g. f/8- f/11 perhaps).
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