Leitz 50mm f/4.5 Focotar LFE

[ulf]

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 LFE

 

Manufacturer:Schneider Kreuznach for Leitz Wetzlar, Germany

Manufacturer's lens designation: FOCOTAR 1:4.5/50 (DOOHF, 17581A)

Currently manufactured: No

Lens type: Enlarger lens for film up to TBD

Design: Five element Gauss design, with three elements before the diaphragm. It has larger diameter front and rear elements than the 16781R and 17582 designs.

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: 1970

S/N of test object: 11 897 509

Manufacturing year: 1970 and 1972

https://www.l-camera..._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 LFE lens transmits 1-75% in an increasing slope from 351nm to 400nm.
  
• T_VISmax (%) = 90%
  
• T_400nm (%) = 75%
  
• T_365nm (%) = 26%
  This low percentage is an indicator for long exposure time under typical UV-pass filtration peaking around 360 nm or when using 365 nm UV-LED illumination.
  
• λ_{UV HMvis}(nm) = 372nm
  
• λ_{UV HM400} (nm) = 369nm
  
• λ_{UV Zero} (nm) = 351nm
  
• These three values indicate that the lens is only working well for upper UV-A 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 LFE

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 LFE

 

UV-Log, Focotar 50mm f/4.5 LFE

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: