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-   -   Mamiya Press Universal-Register/Lens distances (http://www.rangefinderforum.com/forums/showthread.php?t=128144)

europanorama 01-12-2013 21:25

Mamiya Press Universal-Register/Lens distances
 
Need to know which lens-50 or 75mm is nearest to the film-plane.
Must know:
1. mamiya register-mount to film-plane
2. distance rear-lens to film-plane or to mount. 50 and 75mm
Pls put the lens on flat surface and measure distance to the mount-position.

Must learn this to know if a lens can be mounted which must be positioned at 24mm(rear lens) from the film-plane to be sharp at infinity.
Thank you very much

charjohncarter 01-12-2013 21:36

I have the Super 23, and I tried to find the distance which is called 'mount registry.' Let me know if you find out anything.

europanorama 01-12-2013 21:53

Since mount registry must be precise it should be found but it is not listed in some lists.
the other distances: to the filmplane or the mount need not be precise.
Just want to know if its possible.
How big is the mount-diameter? If the lens is too thick then i must use a fotoman or gaorsi or dayi.

charjohncarter 01-13-2013 21:02

I'll measure my mount diameter tomorrow, but it will be rough. Is that OK?

hamradio 01-13-2013 21:14

I'm getting a mount diameter of 77.80mm on a 100/3.5 collapsible and a caliper that is +/- about .02mm.

I do not know the register distance, nor exactly how I'd go about measuring it on the breech-lock system on my super-23 and accounting for the film plane being recessed a few mm in the back.

sevo 01-13-2013 22:57

Quote:

Originally Posted by europanorama (Post 2051265)
Need to know which lens-50 or 75mm is nearest to the film-plane.

The nodal point of the 50 obviously is 25mm closer... ;)

If you want to know the rear element distance, the 50mm has the very short rear lens to film plane distance characteristic for Biogon type lenses - I'll measure that on occasion.

Never had a 75mm - but if the Internet is right, it is another Biogon type so that its distance will be a bit bigger (probably less than the 50:75 ratio - you'd have to get the image circles into the calculation as well). Besides, from pictures (where the outer surfaces look flat rather than strongly curved) I do suspect that the common belief that it is a Biogon clone might be way off the mark - it looks more like a generic (Super Angulon type) large format wide (Zeiss also made a few large format wides of similar type, which they marketed as Biogon, causing some confusion between Biogon brand and Biogon type), whose geometry would be very different.

As far as the mount distance is concerned: How do you propose to measure it, given that it has no proper flange? Breech lock mounts generally need some calibration block inserted in place of a lens to create a artificial reference point for measurements - and I am not aware of anybody (presumably apart from Mamiya service) owning such a thing.

europanorama 01-21-2013 04:56

backfocus and aerial lenses
 
I need only approx. distances, i will tell you why below.

1. register
pls measure distance between the plane where the lens is sitting and film-plane.

2. distance of rear-elements(50 and 75mm) to film-plane.
= register minus rear-lens to mount-plane.
pls measure distance of rear element to mount-plane by position the lens on table.

Reason for asking:
I want to mount aerial lenses which have 21mm and 24mm backfocus distances on eighter mamyia press or other cams like goarsi, fotoman of dayi.
I still dont really understand backfocus-distance. is it the distance of rear element to film to set sharp infinity?
because of these short backfocus-distances i must really forget mirrorcams like rz67 or hasselblad 2000, right?

europanorama 01-21-2013 05:36

back focus, usually defined as the distance from the lens' rear vertex to the film plane when the lens is focused at infinity.

europanorama 12-06-2019 05:09

Still no answer.
Maybe i have found on Super 23 61mm could this be true? using G-groundglas, distance to base where lens is laying.

I deleted report about Dora Goodman Zone Z1 since everything ok-almost. lens was not mounted properly..
Update in FB Medium and Largeformat. They are in Budapest. Multiple camsystems.
I could copy it here but which section?
NO RF anymore, Mamya Universal Press/Super 23-lenses, G-backs.
New options coming in january. LF-helicoids.
Where to post?


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