Leitz 50mm f/4.5 Focotar-2

[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-2

 

Manufacturer: Leitz Wetzlar, Germany

Manufacturer's lens designation: FOCOTAR-2 1:4.5/50

Currently manufactured: No

 

Lens type: Enlarger lens for film up to TBD

Design: Six element Gauss design with three elements before and three elements after the diaphragm

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: 1974

S/N of test object: 2755005

Manufacturing year: 1975

https://www.l-camera...2_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-2 50mm f/4.5 lens transmits 0-76% in an increasing slope from 306nm to 400nm.
  
• T_VISmax (%) = 84%
  
• T_400nm (%) = 76%
  
• T_365nm (%) = 69%
  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) = 330nm
  
• λ_{UV HM400} (nm) = 328nm
  
• λ_{UV Zero} (nm) = 306nm
  
• These three values indicate that the lens is working well 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-2 50mm f/4.5

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

 

UV, Focotar-2 50mm f/4.5

 

UV-Log, Focotar-2 50mm f/4.5

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-2 50mm f/4.5 must be used with a helicoid or macro bellows to set desired magnification. The lens's long FFD easily permits focus to infinity with careful sizing of the helicoid or bellows.

 

 

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Image samples:

 

UV captured 2018-04-09 (YYYY-MM-DD)

Camera: Canon Eos 60D full spectrum modified

Filter-stack: S8612, 2mm + U-360, 2mm

Focotar-2 8s f/11

Lightsource: Sunshine

 

100% crop of image above.

[ulf]

Added some UV-image samples.

This lens is sharp!

Motif as usual a Tussilago