Detailed Instrument Description
The sophisticated design of the 23APO delivers a number of optical, mechanical and application innovations targeted at expert users:
- 120 lp/mm resolution with at least 50% Modulation Transfer Function (MTF50)
- 70,0 mm image circle to cover film/sensor formats including Micro 4/3, APS-C, Full Frame 24x36mm and medium format 33x44mm.
- 74,9 mm rear focal distance to ensure easy adaptation to nearly all film or digital camera mounts in production in 2019. The 23APO requires the use of an appropriate Hasselblad V-mount lens adapter for use with the target camera. The 23APO is not designed to be used on Hasselblad cameras due to mechanical incompatibilities.
- An optional, fully mechanical Shift Adapter provides the correct adaptation of the 23APO to cameras with Canon EF- and Nikon F-mounts. The adapter shifts laterally ±12mm and rotates 360° continuously around the optical axis with spring-loaded detents every 45° starting at Top Dead Center.
- Aperture control is fully manual with no dependencies on electronics, ensuring its compatibility with all camera systems. All f/ stops are adjusted steplessly with no detents using a German-made, 15-blade iris unit. Each f/ stop and in-between stops are marked on the aperture control ring. Point Spread Function (PSF) diameters in microns (µm) indicate corresponding lens performance at each lens opening.
- Focusing control is fully manual with no dependencies on electronics, ensuring its compatibility with all camera systems. A 90° rotation of the focus control ring brings the focused distance from infinity to the minimum focusing distance (from the front element) of 25cm or 10”. Distances are marked in meters and feet.
- An NWS Instruments invention: the built-in leveling feature
- The top of the leveling knob on the lens barrel is perfectly level with the top of the NWS Instruments Akrobat™ Modular Instrument Positioning System front frame, and a suitable carpenter’s level can be used to enable leveling.
- When the leveling knob on the lens barrel is removed, an optional, 16mm circular Wyler AG spirit level, Art Nr. 173-16-120, can be placed directly on the lens barrel to enable lens leveling with 20-30 arcmin sensitivity.
- An NWS Instruments invention: the 2mm-thick reversible, retractable lens hood
- The lens hood can be used in 2 positions: extended or retracted. In its extended position, it offers maximum protection from stray light intrusion without obscuring any part of the object image. In its retracted position, it enables the widest possible coverage angle especially relevant when the lens is tilted, shifted, swung or used with rise/fall.
- The lens hood is held in place in either extended or retracted position using Nylon-tipped spring-plungers on the lens barrel. When a position change is required, the lens hood is simply released from its current position by overcoming the light pressure exerted by the spring plungers.
- In the extended position, the lens hood is fitted on the lens barrel and securely positioned through four 1mm lands radially positioned on the lens barrel diameter. These lands work in combination with the spring-plungers to position the lens hood correctly, as well as providing load-bearing surfaces for resting the front of the lens hood on a horizontal surface.
- In the retracted position, the lens hood is fitted on the lens barrel and its 4 protrusions dovetails into the lens barrel. The spring-plungers on the lens barrel hold the lens hood in its position. The glass of the front element is fully exposed to enable maximum displacement potential.
- At the base of the lens barrel is a 360° scale around the circumference of the lens barrel. It is reserved for future feature implementations.