In Thailand, the groom brought two rolls of AEROCHROME-III (120 type/70mm). These are cut down from aerial photography rolls. AEROCHROME requires special interpretation. Some notes about the emulsion:
- Chemistry: Aerochrome-III is a triple-layer emulsion film with embedded dye couplers; it is designed for compatibility with process AR-5. It can be processed in E-6 chemistry, but this causes loss of dynamic range and excessive levels of contrast.
- Subtractive Dye-Destruction Process: All types of Aerochrome and EIR film use a subtractive image-generation process. Rather than adding dyes to create color where it is wanted, one selectively bleaches and destroys dyes where they are not wanted; the film is by default pure black. This is the reverse of typical printing processes; imagine a typewriter or printer which is fed pure-black paper and creates text by applying bleach to parts of the paper that should be rendered as white: this is how Aerochrome works.
- Infrared Sensitivity: One of the three layers of Aerochrome-III is sensitive out to roughly 870 nanometers. This is the red layer of the film.
- Similarity to Kodak EIR: Aerochrome-III is similar to Kodak EIR, and shares many of its peculiarities. The main difference is that, as a non-E6-native emulsion, Aerochrome has even poorer dynamic range than EIR under standard development (which is really saying something).
Through its sensitivity to infrared light, Aerochome-III is capable of producing images that can’t be produced in any other way – not with digital cameras, nor with PhotoShop or other image-manipulation tools, nor with any conventional film. Its infrared sensitivity is especially an asset for aerial photography; hence the name “AeroChrome”. Particularly, AeroChrome-III is excellent for identifying camouflaged entities in wooded or jungle areas, and for tracing the spread of crop diseases. However, in practice, this film is a nightmare to use, for the following reasons:
- High Cost: Aerochrome-III is only available from a single person, who has an absolute monopoly on its distribution. He lives in Munich and keeps stashes of the stuff in refrigerators in his garage. Within those refrigerators is the entire world’s stock of Aerochrome-III. He’s quite nice, but the fact is, monopolies lead to high prices, and extreme monopolies lead to extremely high prices, especially when supply is constrained and no substitutes are available. A single roll of Aerochrome-III (70mm format; enough for 12 photographs) typically costs several hundred dollars. Ouch.
- Complex Development: Aerochrome-III is difficult and expensive to develop. The chemicals involved are both costly and exceedingly toxic; the development process requires a large number of steps; very high cleanliness is required to develop this film properly; the entire process must be done in absolute darkness. Very tight temperature control and time control are needed – if a chemical reaction is run at just one-tenth of a degree too hot or too cold, the film will be ruined. During development, necessary chemical reactions themselves release heat, and this further complicates temperature control. Many commercial processing rigs use infrared sensors to measure chemical concentrations, but since Aerochrome-III is itself sensitive to infrared, it is therefore incompatible with virtually all commercial processing rigs. Oh no.
- Poor Stability: This film has the shelf life of raw chicken. It needs to be judiciously refrigerated from the moment it is manufactured to the moment it is developed; refrigeration between exposure and development is especially important. It has by far the worst shelf life of any film your groom has encountered.
- Focusing Problems: Lenses work because the speed of light in glass is different than the speed of light in air. This variation in the speed of light is exploited to bend and focus light. Unfortunately, infrared light slows down in glass much more than does visible light, which means that a lens needs to be set differently for AeroChrome than for other types of film. Humans can’t see infrared, which means that we can’t focus lenses properly in the infrared spectrum; we can’t focus on something we can’t see. Electronic focus systems also won’t work. Focusing a camera loaded with AeroChrome requires calculations and measuring tape, and is therefore both slow and error-prone. It takes some practice to characterize the behavior of a lens in the infrared spectrum, and this practice means wasting (very expensive) film. The Groom thanks the Bride for her patience.
- Filtration Requirements: Typical films contain an anti-halation backing. This backing exists because the light-sensitive layers of film are never fully opaque; they are translucent, and this means that there is always a chance of a photon penetrating all the light-sensitive layers of the emulsion. When this occurs, it is important that the photon be stopped; if it is not stopped, it may bounce off the polished film plate at the back of the camera and reflect around inside the camera, potentially bouncing back and hitting the film and causing all sorts of trouble. To prevent this, every film you can think of has a specific layer (called an “anti-halation layer” or “anti-halation backing”) behind all of the light-sensitive layers. These layers absorb rogue high-energy photons and prevent them from causing trouble. However, Aerochrome-III has no such layer, due to problems with chemical incompatibility. This means that special filters must be used when shooting Aerochrome-series films, in order to prevent high-energy photons from entering the camera in the first place. These filters are expensive, fragile, difficult to find, and a pain to use. What a bummer.
- Manufacturing Problems: Aerochrome-III is poorly manufactured. The film typically comes from the factory covered in scratches and gouges, which are plainly visible on finished images. The film is cut sloppily and tends to wrinkle; it’s often slightly over- or under-sized, making loading difficult. The stock is also much thicker and stronger than conventional film, which sounds great, except that cameras occasionally jam, and when a jam occurs, it is in fact desirable that the film stock break, rather than the camera itself breaking; the film should be the “weakest link”. Through its exceptional tensile strength, Aerochrome is infamous for breaking cameras. The film often arrives damp, dusty, and covered in mold, so enjoy cleaning mold off your brand-new $200 roll of film (good for a whole 12 pictures).
- Variable Speed & Metering: Film speed refers to the sensitivity of a film to light; it is often measured in ISO, and is a critical parameter in setting up a camera for a photograph. Unfortunately, the speed of Aerochrome-III changes substantially with altitude above sea level, and also with aging. Standard light meters can’t measure infrared, either. This makes getting correct exposure an exercise in frustration.
The groom recommends carefully reading and understanding the following documentation before looking at photographs taken on any Aerochrome or EIR emulsion:
Here are the frames – the Groom forgot to use a UV-blocking filter in one instance: