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Early lens cap for LTM Summicron 50


JWPATE

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Hi fellows, and this posting is being moved here, to a new thread so as to not go too far field in that of ironringer.

 

The subject here is simply to try and learn more about the early lens cap on the left, as used with the screw-on Summicron fifty lens, with mine being from a 1952 batch. As seen below the style is different from that used on the later lenses of this 43 mm size. Don't know when exactly the change took place, but the cap on the right side is from my M6 camera from about 1997.

 

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I have not yet figured how to get more images than one per post, so will have to do it this way for now.

 

Below is the same two caps seen from the back side, and it is here that I am hoping for information. That newer cap uses a felt-like material inside the rim section which is sort of dark wine color. and I understand is actually a velvet fabric . It is the original material, I believe, but I doubt it was used back in the 1950 era of that left cap.

 

The old cap needs restoration and that is the reason for looking into this somewhat obscure topic. But I, for one, have just not been able to determine what material should be used to restore the old cap. For one thing, it isn't wine colored. And for another it doesn't look much like felt or velvet.

 

To add to the confusion, I have only had the lens for 20 years or so. It would seem most likely that it has already had the lining material replaced before I came along.

 

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So here I begin to remove the old padding from the cap, and to my great surprise I find that it is made of split-hide leather, with the finish side innermost. Quite a thin leather it was, somewhat less than a mm in thickness.

 

Also, there is now no doubt that it is from a replacement job, for underneath I found fragments of the original (or at least older) padding - and it too was thin leather.

 

I believe the color was black, though after all these years it is certainly possible that all of the original is absent, and both the layers I found could be replacement material.

 

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The strips of leather had been glued in with a product very similar to 3M upholstery glue as used today. Here it is carefully removed with the aid of q-tips soaked in acetone.

 

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I cannot find confirmation that the original padding was in fact leather or something else. And before even starting on the project I had searched around for a suitable fabric material. Convinced that it was never just felt glued in, the search for a quality velvet for the job led me to fellow member Jon Goodman in Texas. He was kind enough to supply me with an excellent self-adhesive velvet in a couple of thicknesses, both being less than 1 mm.

 

Inside the cap, I start with a paper template and discover that 5.5 mm wide and 135 mm long is what we need. Only the thickness needed is in question, so I started with the thicker of the two samples.

 

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So with the thicker of the two velvet strips in place the cap was too loose a fit. Therefore, I added also a 5.5 mm strip of the thinner material, right over the first strip, and the result is just right. It totals still something under a mm in thickness, as did the leather, and the fit-up to the lens is sweet. Not too much a push needed, and not a chance of falling off.

 

At this point I am more than satisfied with the cap and its fit, but of course I do wonder how long it will last - that is, with the second strip self-adhering only to the velvet surface of the first.

 

I hope someone my age but with better memory happens along, and is able to set me straight. I still wonder whether leather might have been the original material of choice.

 

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To my knowledge the only material Leica has ever used to keep the lens caps snug on the lens has been a velour-like material which was glued on to the inner diameter of the cap. I have never seen the leather material you are describing. This must have been added later as a "repair" by someone. Some of the later silver chrome caps supplied by Leica (late 90's) used a ribbed, soft plastic material which did not work as well as the velour material used earlier.

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Yes, me too think that the classic material has been only the well known velvet/felt, and, for what I have seen, always of the same pink/magenta color... I have not that old Summicron cap, but have caps that are much older (prewar caps for lenses like the Hektor 7,3 or the Elmar 10,5) and they all have the perennial velvet/felt... which, btw, is used also on several hoods (the two above prewar lenses, for instance.. and the Thambar 90 too).

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