The Citoskop is a stereo plate camera with a reflex waist-level viewfinder (a stereo TLR), made by Contessa-Nettel from about 1924, and continued in production after the merger that created Zeiss Ikon. Immediately after the merger, the camera was Zeiss Ikon's model 315, and was still marked on the front for Contessa-Nettel; later (after about 1928), cameras marked for Zeiss Ikon were model 671/1. The Citoskop resembles Voigtländer's earlier Stereflektoskop (from 1914 onwards). It makes 4×4 cm stereo pairs of images on 45×107 mm plates, in a rapid-changing magazine back.
The camera has two 6.5 cm f/4.5 Tessar taking lenses, in a dial-set Stereo-Compur shutter, with speeds 1 - 1/250 second, plus 'B' and 'T'. The viewing lens is a 6.5 cm f/4.5 Sucher-Triplet, also by Carl Zeiss. It is positioned centrally between the two taking lenses (and in line with them).
The aperture and shutter speed controls are both dials on the front of the shutter unit. The shutter release is on the right-hand end of the top of the shutter unit, and is threaded to take a cable release. The camera is focused with the knob on the left of the shutter unit. The focus scale is on the top; it focuses down to one metre. The camera allows front rise and fall. Whereas on the similar Voigtländer Stereflektoscop and Franke & Heidecke Rolleidoscop the lens panel simply slides under finger pressure, the front rise on the Citoskop is geared, via the knob on the right of the shutter unit.
The viewfinder is a ground-glass screen in the top of the camera body, with a condenser. There is a folding hood, which incorporates a Newton-type viewfinder. There is a loupe in the hood, and a spirit level next to it.
- McKeown, James M. and Joan C. McKeown's Price Guide to Antique and Classic Cameras, 12th Edition, 2005-2006. USA, Centennial Photo Service, 2004. ISBN 0-931838-40-1 (hardcover). ISBN 0-931838-41-X (softcover). p213 (as a Contessa-Nettel camera) and p1039 (as Zeiss Ikon).
- Contessa-Nettel Citoskop with Zeiss Ikon accessories (plate magazine back and rear ground-glass focusing screen) sold in the fifteenth Westlicht auction, in May 2009. The plate magazine is interesting in itself: it has a control to select between normal plates and Autochrome; these, having the emulsion on the back, would have to be positioned further forward for correct focus.
- Citoskop at Early Photography.
- Citoskop (with a third-party back for 135 film) and original advertising information about the camera (in German), at Welt der Stereoskopie.
- Citoskop sold in October 2011 by Auction Team Breker in Cologne. This example is fitted with a single plate holder.