The cameras used in the Apollo program ...
All the photographs taken by NASA astronauts during the Space Race were obtained with special cameras specifically modified for use in orbit. These were designed and built by the prestigious Swedish company Hasselblad. The choice of the brand that would supply the imaging hardware to record America's adventure in space came about almost by chance. At first, in fact, NASA regarded photographic documentation of spaceflights as a formality of secondary importance. The true historical significance of this activity was, however, undoubtedly brought to light by astronaut Walter Schirra, who on the orbital mission Mercury 8 took with him, aboard the Sigma 7 spacecraft, his own personal Hasselblad 500C camera. This model, of course, had not been designed for spaceflight, but it undeniably gave excellent results in capturing the superb views of the Earth seen from orbit. When NASA realized how spectacular Schirra's images were, it became convinced that the Hasselblad brand had everything it took to lend prestige to the historic events that were about to unfold.
And so the American space agency commissioned the Swedish manufacturer to produce a camera model that could also be used in the hostile vacuum of space. The key requirements were the simplicity of use and extreme ease of handling of the camera when adjusting shutter speed, aperture and focus, even with hands made clumsy by the heavy gloves of a pressure suit. After a few months of ingenuity and redesign, the first models of a camera destined soon to become a true legendary hero of the space age were introduced: the modified Hasselblad 500C. These cameras made it possible to capture unforgettable views of the Earth during the last Mercury missions, the historic spacewalks and the rendezvous between spacecraft of the Gemini program, up to the first mission of an Apollo capsule in Earth orbit (Apollo 7). Then, starting with the Apollo 8 mission (the first to orbit the Moon with humans on board, at Christmas 1968), the Hasselblad 500EL with electric motor was introduced for the first time, allowing automatic film advance and precise shutter control. From then on, this model would faithfully accompany all the Apollo missions, soon reaching the lunar surface as well ...
The Hasselblad 500EL camera supplied to the Apollo missions came in two specific versions:
- a model designed for use inside the spacecraft (CSM and LM), called the 500EL (HEC);
- a model designed for use in the vacuum of space and on the lunar surface, called the 500EL Data Camera (HDC).
Both models could take three main types of lenses:
- a standard Zeiss Planar 80 mm f/2.8 lens;
- a Zeiss Biogon 60 mm f/5.6 wide-angle lens (the lens par excellence for moonwalks);
- a Zeiss Sonnar 250 mm f/5.6 telephoto lens.
Each lens could be fitted with a polarizing filter to reduce the strong glare found in space or on the lunar surface. The model built for extravehicular activity was made using light metal alloys that allowed it to work even in extreme environments. Besides giving considerable sturdiness to the camera, these materials had been specially painted silver, so as to effectively reflect outward most of the incident electromagnetic radiation (visible light, ultraviolet and infrared). The Hasselblad 500EL was an extraordinary camera, designed to withstand large temperature swings that could range between +120°C and -65°C, depending on whether it was lit by the Sun or exposed to the icy shadow of space. Its mechanism had also been optimized to prevent jamming of the film or of moving parts such as the shutter, and it could work without conventional terrestrial lubricating oils , which would have inexorably evaporated in a vacuum. Throughout the Apollo program, the Hasselblad 500ELs worked flawlessly. Only during the Apollo 16 mission did one of the two cameras used on the lunar surface show a series of anomalies. It was later established that these were due to the harmful effects of abrasive lunar dust, which had most likely got into the mechanism during a magazine change carried out with contaminated gloves. This Hasselblad showed occasional jamming problems, as well as obvious physical contamination and scratches on the frames, visible in many of the shots taken during the exploration phase of the mission (see the Apollo 16 photo gallery at the following link: https://apolloarchive.com/apollo_gallery.html). Unlike conventional models used on Earth, the lunar cameras used film rolls enclosed in special shielded magazines which, besides protecting the film from the rigors of the vacuum and from electromagnetic radiation, proved extremely easy to handle and practical to change. The format used was the classic 70 mm supplied by Kodak, which for the first time in history produced it specially for NASA on a much thinner polyester film base a full 12 meters long. This solution was optimized to allow 200 exposures for black-and-white magazines and 160 for color ones, far exceeding the standard 12 exposures of the rolls sold to the general public. When used on the lunar surface, the Hasselblad 500EL HDC was attached to the chest of the spacesuit by a metal bracket. This practical position allowed the astronaut to point it more easily at the scene to be photographed and to handle it freely with both hands to set the shutter speed, the aperture, the focus, or to change a film magazine or the lens. Shutter speed, aperture and focus were adjusted with three dedicated rings (fitted with protruding metal tabs for an easier grip) mounted on the interchangeable lenses. This ingenious design let the astronaut adjust them at will, checking the click-stop positions of the rings thanks to their position at the front, which made them easy to see by looking down from inside the spherical helmet. The picture was taken with a dedicated button under the lens that could be pressed with either hand, or with a dedicated trigger, mounted on a protruding handle placed under the camera itself. The Hasselblad 500EL HDC had no optical viewfinder, let alone the classic waist-level viewfinder found on terrestrial models. Using such devices would have been completely impractical, since the astronaut could never have brought them up to his eye because of the bulk of the pressurized helmet. Aiming at subjects therefore required long training sessions on Earth before the mission, in order to perfect the "by eye" estimate of the framing, physically moving the whole torso. The absence of a viewfinder explains why many of the photographs taken by the Apollo astronauts are often off-center or tilted relative to the position of the subject. Despite the techniques developed from mission to mission, perfect composition never became the norm. We must always remember, however, that the astronauts had come to the lunar surface for scientific and exploration purposes, certainly not to play wedding photographer. The documentation work they did, however, was of excellent quality and made it possible to greatly expand the geological understanding of our natural satellite.
A crucial technical feature of the lunar camera was the Réseau Plate (Réseau Plate), installed right against the film. It was a tempered glass plate engraved with a grid of small opaque reference crosses, also known as "fiducial markers". The purpose of this device was to superimpose on the film a series of crosses spaced with millimeter precision, which made it possible, after the mission, to calculate and measure accurately the distances and angular proportions between the objects photographed. This method was already used in military aerial photogrammetry. Since there are no familiar size references on the lunar surface (such as a house, a tree or a road), it became extremely difficult to deduce the true scale of geological features. To complicate 
Apollo 16 - Stone Mountainthings further, the lunar horizon inevitably appeared closer and more curved than the Earth's, because of the large difference in radius between the two bodies. All these factors combined made every perspective calculation a real headache, especially considering that the photographs were often the only investigative source available to shed light on the many topographic questions. For these reasons, the Réseau Plate was the mathematical keystone. The fixed angular distance and marked by the crosses made it possible to obtain proportions and distances with extreme precision using trigonometry. The plate used in the Hasselblad HDC measured 54 x 54 mm (the usable exposure area on the film). Each plate carried 25 crosses in all, arranged in a 5 x 5 matrix. All the crosses were the same size, except for the central one, which was about twice as large to mark the exact center of the frame and the optical axis of the lens. The intersections of the crosses were exactly 10 mm apart, with an engraving tolerance of just 0.002 mm. So, with a 60 mm lens fitted, the distance between the crosses translated into an apparent angular separation of about 9.5°. With a 250 mm telephoto lens, on the other hand, the separation became much narrower. This grid made extrapolations extremely accurate for measuring the height of a mountain, the distance of a crater or the size of a boulder. Although they were physically engraved and opaque, the Réseau Plate crosses were very thin. Their visibility on the film depended on the shooting conditions and the exposure.
If a subject in the frame was extremely bright or white, it was very likely that the black outline of the cross would be hidden by the persistence of the chemical glare recorded in the image (a phenomenon called blooming or bleeding). This is exactly what happened in the famous frame AS16-107-17446 (Apollo 16), taken when the astronauts stopped at Stone Mountain to point the antenna toward Earth. On that occasion they photographed the wonderful Cayley Plateau; one cross in that frame appeared literally "swallowed" by the white glare from the Rover's antenna. Although the reasons for this optical disappearance are obvious and scientifically impeccable, the photo inexplicably ended up in the conspiracy meat grinder, feeding the delusional claim that the cross "hidden" behind the antenna was the smoking gun of a photomontage. However, this trivial phenomenon occurs in exactly the same way on Earth: if you try photographing on film a hair placed in front of a powerful spotlight or an overexposed sheet of paper, you will notice that the dark outline disappears, absorbed by the surrounding halo of light. It is a perfectly normal reaction, due to the photochemical characteristics of the emulsions, and certainly not to the harebrained and absurd post-production manipulations invoked by conspiracy theorists.
It should be pointed out that the Hasselblad HDC cameras had neither a light meter nor autofocus; they were strictly manual. The choice of shutter speeds and apertures was entirely up to the astronauts, who had been specially trained to judge the right combination "by eye". The shutter speed ring ranged from B (Bulb) (shutter open as long as the trigger was held down) to a very fast 1/500 of a second, by way of intermediate settings (1s, 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250). The aperture ring adjusted the diameter of the opening that let in the light and worked in steps going from the widest aperture (f/2.8 or f/5.6 depending on the lens) to the smallest aperture (f/22). The widest apertures (f/5.6) were used for photographing subjects in shadow; the narrower ones (f/8, f/11) were used for subjects harshly lit by the Sun. Unlike the others, the focus ring turned smoothly without click stops, allowing the astronaut to estimate the distance in meters (zone focusing) or to set it to infinity for distant panoramas. Since the Hasselblad 500EL was a fully manual camera, pre-mission training was also largely devoted to mastering these techniques while shut inside the bulky A7L suit. The costs of the Apollo program were astronomical: the whole enterprise cost American taxpayers 25.8 billion dollars, equal to more than 250 billion in today's dollars. Every minute spent on the lunar surface had an incalculable value. It was vital to optimize timing and reduce the margin of photographic error to zero. For this reason, the position of every single shot was rigorously planned in the flight plans and refined during simulations on Earth.
This careful planning was made possible by the predictable, constant characteristics of the lunar environment: total absence of atmosphere (and therefore of clouds or haze) and a very slow change in the Sun's height above the horizon. All the Apollo missions landed deliberately in areas close to the lunar terminator, where it was early morning and the Sun was very low. This grazing angle produced long shadows that emphasized the relief of the craters (helping the pilot during the descent) and ensured great thermal stability. The Moon's rotation is in fact very slow (a lunar month lasts 29.53 Earth days, divided into about 14.75 days of uninterrupted light and 14.75 of darkness). By landing in the morning, the astronauts worked on ground that was still slowly warming up, keeping outside temperatures within manageable limits (+50°C) for the life support systems. This lighting, stable for hours, made it possible to plan well in advance exactly where, how and with what settings to take the photographs.
It is therefore clear why the flight plans listed the photographic coordinates in painstaking detail. Every planned shot rigorously took into account the position of the Sun. From this data, memorized or printed on the cuff checklists of their suits, the astronauts worked out the correct exposure on the fly. Given the hectic pace of the extravehicular activities (especially on the longer J missions such as Apollo 15, 16 and 17), it was very often Mission Control in Houston that radioed the crews the exact settings for the Hasselblad. To avoid nasty surprises, the astronauts systematically used the bracketing technique, taking several shots of the same subject while changing the aperture by one step ; this mathematically guaranteed that they would bring home at least one perfectly exposed photograph. The basic exposure guidelines according to the Sun angle were even printed on handy orange labels stuck directly on the back of the magazines. During the Apollo 11 mission (in which the very first steps on another celestial body were taken) almost 1,400 frames were taken in all on the 9 magazines used during the entire mission, including the landing in the Sea of Tranquility (857 black-and-white and 550 color). To pare down the weight of the Lunar Module for the critical lift-off phase into orbit, a strict directive was applied: only the astronauts, the rock samples and the precious magazines containing the exposed film would come back from the Moon. The Hasselblad HDC cameras used (12 in the whole program) were instead stripped of their magazines and deliberately left on the lunar dust to save precious kilograms of payload. They still lie today in those alien deserts, in an unchanging environment where the silent wear of time changes only the length of the shadows. Today, all the historic photographs taken during the Apollo missions have been digitized at very high resolution and are freely available on the Project Apollo Archive website (www.apolloarchive.com).
