A large format lens with a 45mm focal length and f/4.5 aperture, typically for view cameras.
The Schneider Apo-Sironar 45mm f/4.5 is listed as a large format lens in the Apo-Sironar line; however, the standard Apo-Sironar range begins at 90mm. A 45mm focal length in the Apo-Sironar designation is atypical — this may refer to the Schneider Apo-Digitar 45mm f/4.5 (designed for digital medium format scanning backs), or a different product with a transcription error in the canonical name.
45mm focal length, f/4.5 maximum aperture. If Apo-Digitar: digital medium format scanning back coverage, Copal shutter. If large format: unusual focal length for Apo-Sironar series — verify against product documentation.
The Schneider Apo-Digitar 45mm f/4.5 was produced for digital scanning backs on view cameras and medium format systems — designed for flat-field coverage of CCD scanning sensors rather than large format film. If this is the Apo-Digitar, it is optimised for digital sensor coverage at infinity focus with high resolution. The Apo-Sironar series does not include a 45mm focal length in standard production.
Verify the actual product against barrel markings — confirm whether this is an Apo-Sironar, Apo-Digitar, or another Schneider 45mm formula. Check Copal shutter operation. Inspect glass for haze. Note: the canonical name may contain a transcription error.