ulf Posted February 21, 2021 Share Posted February 21, 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 100mm f/4.5 Focotar-II Manufacturer: Leitz Wetzlar, GermanyManufacturer's lens designation: FOCOTAR II 1:4.5 / 100 - LEITZ WETZLARCurrently manufactured: NoLens type: Enlarger lens for medium format filmDesign: TBDFocal length: 100mmAperture range: f/4.5 – f/22, Manual, 8 bladesFormat coverage: TBDRecommended magnification range*: TBDOptimal magnification*: TBD*Definitions reversed from normal enlarger definition, referring to the motif not the negative-planeMount: M39 x 26tpi threadReverse mount: None.Helicoid: NoFlange focus distance: TBDFront filter: 49mm filter threadIntroduction year: 1974S/N of test object: 2841030Manufacturing year: 1977https://www.l-camera...-_1:5.6_/100_mm For a short time, before I returned it, I had a lens that was slightly younger.It had the serial #3065653 indicating that it was produced 1981.That was the last year the Focotar-II 100mm was made.That lens showed a similar transmission as this lens tested here. Lens review (VIS), on the web:Lens Manual on the web: Transmittance SummaryDefinitions of the parameters belowRange: The Focotar-II 100mm f/5.6 lens transmits 1-74% in an increasing slope from 322nm to 400nm.TVISmax (%) = 89%T400nm (%) = 74%T365nm (%) = 32%This low percentage is an indicator for relatively long exposure time under typical UV-pass filtration and works best with filters that peaks close to 400nm like the SEU3 filter.λUV HMvis(nm) = 372nmλUV HM400 (nm) = 368nmλUV Zero (nm) = 322nmThese three values indicate that the lens is working only for UV-A photography with suitable filters.The unusually gradual slope in UV makes the performance even worse than the 1% cutoff indicates.Image of test object: Spectral Transmission GraphsUV-NIR, Focotar-II 100mm f/4.5The transmission measurement accuracy into the end of NIR range is less good due to limitations in the light source. UV, Focotar Focotar-II 100mm f/4.5 UV-Log, Focotar-II 100mm f/4.5Numerical Spectra Data available: Yes Filters and how to use them on this lens:Beside the front filter 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-II 100mm f/4.5 must be used with a helicoid or macro bellows to set desired magnification.On most cameras the lens's long 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. This lens is not very good for UV-photography but as a macro lens for the very top end of UV, closer to 400nm and VIS it is an excellent very sharp lens.Image samples: Link to comment
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