ulf Posted February 13, 2021 Share Posted February 13, 2021 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, GermanyManufacturer's lens designation: FOCOTAR-2 1:4.5/50Currently manufactured: No Lens type: Enlarger lens for film up to TBDDesign: Six element Gauss design with three elements before and three elements after the diaphragmFocal length: 50mmAperture range: f/4.5 – f/16, Manual, 8 blades Format coverage: TBDRecommended magnification range*: TBDOptimal magnification*: TBD*Definitions reversed from normal enlarger definition, referring to the motif not the negative-plane Mount: M39 x 26tpi threadReverse mount: None.Helicoid: NoFlange focus distance: TBDFront filter: Only by special filter adapter. See below Introduction year: 1974S/N of test object: 2755005Manufacturing year: 1975https://www.l-camera...2_1:4.5_/_50_mm Lens review (VIS), on the web:Lens Manual on the web: Transmittance SummaryDefinitions of the parameters belowRange: 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) = 330nmλUV HM400 (nm) = 328nmλUV Zero (nm) = 306nmThese 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: Spectral Transmission GraphsUV-NIR, Focotar-2 50mm f/4.5The 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/4.5Numerical Spectra Data available: Yes General comments about the UV-reach:tbaFilters 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__1This 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 modifiedFilter-stack: S8612, 2mm + U-360, 2mmFocotar-2 8s f/11Lightsource: Sunshine 100% crop of image above. Link to comment
ulf Posted February 21, 2021 Author Share Posted February 21, 2021 Added some UV-image samples.This lens is sharp!Motif as usual a Tussilago Link to comment
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