kermaier
Well-known
I have a Summicron 50mm Rigid, dual scale, on which the front element assembly/barrel can be unscrewed and removed. Is this part interchangeable with all Rigid lenses (dual-scaled or single), or are there variations on the Rigid that would make this assumption wrong?
::Ari
::Ari
Tom A
RFF Sponsor
Theoretically you can use the front from one and the back from another lens. However, Leica would "batch" lenses within the variations of focal length. All DR that I have owned and seen have been 51.9mm focal length.
In assembly they picked barrels and optical assemblies and matched them. Also inside the back helicoil barrel - the number of the lens is engraved or scratched in. This number should be the same for the focussing barrel as for the "lenshead". If they are mismatched - you most likely will end up with a sub-standard lens. Even a minute 0.1 mm will make a difference. If, for some reason you need to change the barrel - the lens head can be re-collimated and shimmed for the new barrel. This require some rather sophisticated equipment - or a lot of patience and test films!
The process was labor intensive with the original production and is partly responsible for Leica reputation when it comes to lenses. They checked and double checked each lens before it was shipped - and also checked and corrected things like lens element centering - a very costly procedure (can account for 40% of the cost of a lens!).
No wonder some of the old lenses still works so well and still bring good money, even after 50 years!
In assembly they picked barrels and optical assemblies and matched them. Also inside the back helicoil barrel - the number of the lens is engraved or scratched in. This number should be the same for the focussing barrel as for the "lenshead". If they are mismatched - you most likely will end up with a sub-standard lens. Even a minute 0.1 mm will make a difference. If, for some reason you need to change the barrel - the lens head can be re-collimated and shimmed for the new barrel. This require some rather sophisticated equipment - or a lot of patience and test films!
The process was labor intensive with the original production and is partly responsible for Leica reputation when it comes to lenses. They checked and double checked each lens before it was shipped - and also checked and corrected things like lens element centering - a very costly procedure (can account for 40% of the cost of a lens!).
No wonder some of the old lenses still works so well and still bring good money, even after 50 years!
kermaier
Well-known
So it sounds like a risky proposition to take a lens with a nice focusing mount and scratched up front element, and swap lens heads with a lens having a nice front element and a beat-up focusing mount, to make one really nice lens and one totally thrashed lens. 
Oh well.
Oh well.
Erik L
Well-known
So it sounds like a risky proposition to take a lens with a nice focusing mount and scratched up front element, and swap lens heads with a lens having a nice front element and a beat-up focusing mount, to make one really nice lens and one totally thrashed lens.
you could always take some careful measurements first.
kermaier
Well-known
Thanks for the vote of confidence, Erik, but I have neither the instruments nor the know-how to measure a lens' focal length to tolerances of 0.1mm.
Livesteamer
Well-known
I have two Summicrons, one being a DR. The non DR, #2433517 has two little numbers engraved on the lens barrel underneath the word feet. They 19, which I was told was added to the listed focal length (50mm) to give the actual focal length of that lens, 51.9mm. I can't find such numbers on my DR. It is #2356513 so I'm not sure what length it is. Joe
kermaier
Well-known
I have the same 19 engraved under the end of the distance scale (mine is dual scale).
But after unscrewing the lens head, I can't find any sort of serial number inside the focusing mount. Anyone know where to look?
But after unscrewing the lens head, I can't find any sort of serial number inside the focusing mount. Anyone know where to look?
Livesteamer
Well-known
I believe many of Leicas lenses have these little numbers to note their actual focal length. Joe
kermaier
Well-known
Two questions:
1. If two rigid 'crons have the same focal length adjustment (e.g., "19") engraved on the mount, does that mean their heads can be exchanged?
2. Does anyone know where inside the focus mount the serial number is engraved to match to the head?
1. If two rigid 'crons have the same focal length adjustment (e.g., "19") engraved on the mount, does that mean their heads can be exchanged?
2. Does anyone know where inside the focus mount the serial number is engraved to match to the head?
Tom A
RFF Sponsor
In theory two lenses with the same #19 engraved should match - but the only way to find out is to shoot with them - or have them checked on a collimeter. To my knowledge - all DR Summicron's are 51.9 mm focal length.
The number is sometimes engraved and even white filled on the inside flange of the mount. Later Leica just went to writing it with a pencil, rather dimly on the flange. They also used to give the full number, later they only gave the three or four last digits.
The number is sometimes engraved and even white filled on the inside flange of the mount. Later Leica just went to writing it with a pencil, rather dimly on the flange. They also used to give the full number, later they only gave the three or four last digits.