Jump to content
UltravioletPhotography

Leitz 50mm f/4.5 Focotar-2


ulf

Recommended Posts

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.

 


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:


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.
  • TVISmax (%) = 84%
  • T400nm (%) = 76%
  • T365nm (%) = 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.
  • λUV HMvis(nm) = 330nm
  • λUV HM400 (nm) = 328nm
  • λUV 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:

post-150-0-92869100-1613494938.jpg post-150-0-22393100-1613494931.jpg post-150-0-78296900-1613495145.jpg


Spectral Transmission Graphs

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

post-150-0-44839100-1617694664.png

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

post-150-0-63756200-1617694672.png

 

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

post-150-0-61839900-1617694678.png

Numerical Spectra Data available: Yes

 

General comments about the UV-reach:

tba


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.


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.

 

 


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

post-150-0-23197700-1613920217.png

 

100% crop of image above.

post-150-0-31130800-1613920229.png

Link to comment
  • 2 weeks later...

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
×
×
  • Create New...