Camera versus binocular optics in Hitchcock’s “Rear Window”

The other interesting thing about Hitchcock’s “Rear Window” is the fact that the binocular shots, and the camera shots appear the same. Again we could mark this down to artistic license, but there are inherently some issues which persist from an optical point-of-view. Firstly, what kind of binoculars are they? Little is written in the literature about the brand, so that requires a little investigative work.

Jeff with his binoculars in Rear Window

The most telling feature of these binoculars is that these are porro prism binoculars. In Porro prism Binoculars the objective or front lens is offset from the eyepiece. This offset is often characterized by a cap, which terminates the transition from ocular to objective lens.

The cross-section of half of a binocular. showing the transition from ocular (left) to objective (right) lens.

With some manufacturers, the transition seems to be smooth, with streamlined curves. There are a couple of brands that stand out in this respect: Bausch and Lomb (USA), Bushnell (USA), Cadillac (USA, made in Japan). Brands like Zeiss on the other hand, had a capped, “hard” transition.

A pair of Zeiss binoculars, showing the hard black “caps” covering the lenses.

Beyond this, it is hard to tell what brand they were, because those markings would be on the front of the binoculars. More important are likely the power of magnification (how many times closer you are to the thing you are viewing), and the objective diameter of the lens. After doing some comparative measurements of the binoculars in the movie, with those in a early 1950s Bausch and Lomb catalog, I would guesstimate that these are the 7×50 binoculars, i.e. objective diameter was 50mm, and the power of magnification 7 times. A 400mm lens has a magnification factor of ×8, so binoculars with a power of ×7-8 would make sense (if we ignore the optical differences between binoculars and 35mm film lenses, e.g. cameras have a film plane, binoculars don’t).

A comparison of the binoculars in the movie, and the Bausch and Lomb 7×50 binoculars, circa early 1950s – notice the ergonomic flow of the lens parts.

The other factor which makes the B&L 7×50 the most likely candidate is that Bausch and Lomb supplied the US armed forces during WW2 (and Jeff was in the US Army Air Force), and this particular model was the Navy model, which had the “highest relative brightness of any binocular”, a so-called true “night glass”. So what are the issues between the 400mm camera lens and the binocular optics, assuming 7×50?

  • Field-of-View – The FoV of a 400mm lens is just over 5° (horizontal), which at 100′ distance (the width of the courtyard), translates to around 9 feet. The B&L 7×50 binoculars had a linear field of 381′ at 1000 yards, which would be about 12.7′ at 100′.
  • Full image circle – The camera would truncate the image circle of the lens to a rectangle, and therefore the maximum FoV is only possible along the diagonal of the frame. Binoculars allow you to see the full circle of the FoV and thus the maximum FoV in all directions. A 35mm camera with a 3:2 ratio only displays about 59% of an image circle with the same diameter as the diagonal of the rectangular image sensor.
  • Stereo Vision –  Binoculars allow both eyes to see slightly different angles of the same objects that allow use of depth perception. Other than specialized 3D cameras, most cameras are monocular.
Rear Window: The view through the binoculars.

So Hitchcock’s use of both binoculars and a 35mm camera with a 400mm lens does take a lot of artistic license, because they are not the same, but portray the same thing on screen.

Use of the camera in Hitchcock’s “Rear Window”

Last week I watched Rear Window, an Alfred Hitchcock directed thriller from 1954 starring James Stewart and Grace Kelly. The story follows photojournalist, L.B. “Jeff” Jefferies, who breaks his leg while shooting an action shot at a car race (supposedly working for LIFE Magazine). Confined to a wheelchair in his New York apartment, he spends time watching the occupants of neighbouring apartments through his apartments rear window, as they go about their daily lives.  He begins to suspect that a man across the courtyard may have murdered his wife. Jeff enlists the help of his high society fashion-consultant girlfriend Lisa Freemont and his visiting nurse Stella to investigate. It’s a great movie from a period when life was likely a little simpler than it is now.

For the early part of the movie, Jeff is just looking out the window, bored with being confined to his apartment while his cast covered leg recovers. When he deduces something is amiss across the courtyard, he pulls out his camera, with its telephoto lens to view the scene a little closer. The courtyard was supposedly 98′ wide and 185′ in length.

Part of the courtyard.

The 35mm film camera used by Jeff is an Exakta VX Ihagee Dresden, with the Exakta logo covered by a piece of black material in the movie. Why choose the Exakta? In the time the film was shot, there were really only three 35mm camera systems with global recognition: Leica, Contax, and Exakta. Hitchcock could have used a Leica with a reflex housing for the telephoto lens (e.g. Visoflex II), but a solution with a one-eyed reflex with a prism viewfinder was more elegant. Why was the brand covered with black tape? To cover up its East German / Communist origins? This may have played a role, but more likely just an avoidance of advertising in film.

The Exakta is an interesting choice of camera for the period, made by Ihagee Kamerawerk Steenbergen & Co, Dresden, in former East Germany and was produced between 1951-56. The Exakta is notable as being the first ever Single Lens Reflex (SLR) camera for both 127 roll film (1933), and 135 format 35mm film (1936). It’s not surprising that Jeff was using a Exakta, as before Japanese started to dominate the camera market the Exakta dominated the market, capturing perhaps 95% of SLR sales (they did kind of invent the SLR in 1936). The lens being used on the camera is a Kilfitt Fern-Kilar f/5.6 400mm telephoto lens.

The Exakta VX

There are a number of things that are of interest with the use of the camera. I know this is a movie, and the camera was used as a prop, but here goes. Firstly, as a press photographer, it is unlikely he would have used a 400mm lens. Jeff’s character was supposedly based on war photographer Robert Capa, used a Contax II with a 50mm lens. (Ironically Capa was killed covering the First Indochina War in 1954, which is where Jeff’s editor wanted to send him). A 400mm lens would be more useful for a sports photographer shooting field based sports like football (soccer) or a bird watcher. The lens Jefferies uses to take the photograph on the racetrack is clearly a wide-angle (and frankly taken from a very dangerous viewpoint).

Is Jeff pushing the shutter button?

Next there is the issue of the view through the lens itself, which it seems is solely for cinematic effect. I know from a cinematography point-of-view, Hitchcock was trying to imply that the view was through a camera, showing a circular view, but camera views are rectangular. Next there is the issue of the “focal length” of the lens, which seems to be quite flexible. There are two scenes (shown below) taken seconds apart in Thorwald’s apartment, and viewed through the Kilfitt Fern-Kilar 400mm lens. One shows a close-up of Lisa’s hand behind her back (showing where she has slipped on the victim’s wedding ring). This would mean that the 400mm lens had the ability to zoom, which was not possible (and likely act like a 800-1200mm lens). There is also the issue of light intensity, which doesn’t seem to change, even though it is nighttime. The wonders of artistic license.

Two shots, seconds apart, taken with the 400mm lens.

The field-of-view for the 400mm lens is about right for most shots, at 8-9 feet horizontally, and 5-6 feet vertically. At times it looks as though Jeff is taking photos, however the shutter release button is on the photographers left side of the camera, so from this we know he did not take any photographs. In addition, Jeff never actually cocks the shutter, which is a requirement for looking through the viewfinder – the mirror stays up after exposure, so viewfinder is dark, cocking the shutter returns the mirror to normal position (and transports the film to the next exposure).

Lars Thorwald, shown through the framed camera shot, and approximates the FOV of the lens quite well.

Which leads us to the issue of photographs. why would a photojournalist, who takes photographs for a living, not take any photographs of things happening across the courtyard? If he would have taken some photographs, then he would of at least had pictures of suspicious behaviour to show his friend Det. Lt. Doyle. But not once did we hear Jeffries depress the shutter button (and you would hear it because it is noisy). He may have taken photographs at other times, but not during the setting in the movie.

P.S. The lens was manufactured by Heinz Kilfitt Optische Fabrik (1946-64) from Munich (West Germany). Kilfitt was an innovative lens maker, producing the world’s first 35mm macro lens, the Kilfitt 4 cm f/3.5 Makro-Kilar in 1955.