Leitz 50mm f/4.5 Focotar from 1952

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Finalized: Work in progress.

Last Update:

Note: Additional information or links about this lens are welcomed and will be incorporated into the first post as time permits.

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Leitz 50mm f/4.5 Focotar from 1952

 

Manufacturer: Ernst Leitz Wetzlar, Germany

Manufacturer's lens designation: Ernst Leitz Wetzlar Germany, Focotar f=5cm 1:4.5, DOOCQ,

Currently manufactured: No

Lens type: Enlarger lens for film up to TBD

Design: Five element triplet optical design

Focal length: 50mm

Aperture range: f/4.5 – f/16, Manual, 8 blades

Format coverage: TBD

Recommended magnification range*: TBD

Optimal magnification*: TBD

^{*Definitions reversed from normal enlarger definition, referring to the motif not the negative-plane}

Mount: M39 x 26tpi thread

Reverse mount: None.

Helicoid: No

Flange focus distance: TBD

Front filter: Only by special filter adapter. See below

Introduction year: 1952

S/N of test object: 997834

Manufacturing year: 1952

https://www.l-camera...1_1:4.5_/_50_mm

 

Lens review (VIS), on the web:

Lens Manual on the web:

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Transmittance Summary

Definitions of the parameters below

• Range: The Focotar 50mm f/4.5 lens from 1952 transmits 1-76% in an increasing slope from 316nm to 400nm.
  
• T_VISmax (%) = 83%
  
• T_400nm (%) = 76%
  
• T_365nm (%) = 63%
  This high percentage is an indicator for relatively short exposure time under typical UV-pass filtration peaking around 360 nm or when using 365 nm UV-LED illumination.
  
• λ_{UV HMvis}(nm) = 350nm
  
• λ_{UV HM400} (nm) = 348nm
  
• λ_{UV Zero} (nm) = 316nm
  
• These three values indicate that the lens is working for some upper UV-B photography with suitable filters and a few for this, suitable cameras.
  

Image of test object:

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Spectral Transmission Graphs

UV-NIR, Focotar 50mm f/4.5 from 1952

The transmission measurement accuracy into the end of NIR range is less good due to limitations in the light source.

 

UV, Focotar 50mm f/4.5 from 1952

 

UV-Log, Focotar 50mm f/4.5 from 1952

Numerical Spectra Data available: Yes

 

General comments about the UV-reach:

tba

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Filters and how to use them on this lens:

Here is an excellent description by Steve, about how make a filter mount adapter for this lens:

https://www.ultravio...__fromsearch__1

This method works for all versions of Focotar 50mm

 

It is also possible to use rear mounted filters, either in lens mount adapters for mirrorless cameras like Sony A-series etc, or placed directly in the camera.

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Handling and focussing:

This Focotar 50mm f/4.5 must be used with a helicoid or macro bellows to set desired magnification.

On mirrorless cameras the lens's FFD permits focus to infinity with careful sizing of the helicoid or bellows.

However these lenses are designed and optimised for short focus distances. At infinity the result will not be optimal.

 

 

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Image samples: