Hasselblad (Ross) SKa 5

The SKa 5 is the least documented of the four Ross cameras and the largest thing Victor Hasselblad ever built. Evald Karlsten’s biography, quoted by Chernoff on Hasselblad Historical, records that the Royal Swedish Air Force ordered a surveying camera of considerably larger format than the earlier models — 18×24cm, seven by nine inches — and that Ross designed and built it; Chernoff dates production to 1943 and gives 24 cameras. Camera-wiki spells out the prefix, spaningskamera, reconnaissance camera. Beyond that, Chernoff writes, little is known outside several factory photographs, a short description in Afalter’s book, and photographs, a summary and a poor copy of a one-page factory data sheet in Nordin’s Compendium. His own specification page has more entries marked “information requested” than filled.

What is established is the layout, which scales the 1942 SKa 4 up rather than rethinking it. A cast-aluminium body carries an electric motor drive fed from the aircraft’s DC circuit or a battery, interchangeable backs holding 200 exposures of 190mm double-perforated film, a Ross behind-the-lens leaf shutter at 1/75, 1/150 and 1/300, a frame finder, and no flash. The one feature found on no other Ross camera is the film flattener: a vacuum pump built into each back, the standard method in aerial survey cameras for holding a large sheet of film truly flat, which the SKa 4’s presumed cam-lifted pressure plate could not do at this size. Weights are the firmest figures Chernoff has — 24.6kg with a back and the 25cm lens, 29.6kg with the 50cm, plus an 8.1kg mounting bracket and a 3.5kg carrying box. Dimensions he can only estimate from photographs, at roughly 26 × 34 × 36cm, and he rejects Afalter’s 11.2 × 15.0 × 17.5cm because a body that size could not hold an 18×24cm frame. Nordin’s 1998 Compendium calls the SKa 5 another hand-held camera; Chernoff disagrees, on the grounds that it has no handles, no provision for any, and is too big and heavy to hold.

The lenses were all Zeiss, all fixed at infinity, and all — like every lens on a Ross camera — uncoated. Chernoff’s specification lists an Orthometer 25cm f/4.5, a Tele-Tessar 25cm f/4.5 and a Tele-Tessar 50cm f/5.6; his summary table on the introductory page makes the second lens a Tessar 25cm f/4.5 instead, and neither page notes the difference. Afalter’s 150mm f/4.5 he dismisses outright. The Orthometer is the interesting choice. Willy Merté’s 1926 design was Zeiss’s unsymmetrical aerial wide-angle before the 70-degree Topogon replaced it in 1932, and Chernoff, following Kingslake, reads its presence on a 1943 camera as a sign that the older lens was simply what could be had from Germany. None of the SKa 5’s lenses is otherwise recorded in a Hasselblad context, and their aperture scales are unknown.

Whether the SKa 5 was a mapping camera in any strict sense is a question Chernoff raises and declines to answer. A photogrammetric camera must hold its frame and focal length stable against temperature and have its lens centred and set exactly perpendicular to the film, which requires laboratory testing of a kind the Ross shop may or may not have done; with only 24 built, he allows that some may have reached that standard, but says that even with one in his hands he could not tell without instruments. He then follows the ambition forward to the Reseau-plate MK 70 and NASA’s electric data cameras, whose Zeiss lenses were individually fitted and engraved with their body serials — the practice the Ross cameras began.

Almost everything else is open. Serials may run 1–24 or, like the MK 80’s, from 101; no individual number is recorded anywhere. The exposure release, the accessories issued, the aircraft the camera flew in and the end of production are all “information requested” on Hasselblad Historical, and the site has asked since 2008 for anyone who encounters one to record lenses, dimensions and weight and to look for an instruction manual. The Flygvapenmuseum holds a “Flygkamera SKA 5” in its transport box and a lens catalogued as SKa 5 accessory, which are the only located survivors; their records have not been examined for this entry. The SKa 5’s lenses are not given pages of their own here because no source states more than their names.