For all the advances in digital photography, there remains a mystique for photographers and filmmakers about chemical film. Using it presents an artistic and technical challenge, and it lends an aesthetic to your work which is difficult to find in other ways. But particularly when it comes to moving pictures, how many of us have ever ventured beyond the Super 8 cartridge? If you’re not lucky enough to have a Spielberg budget, [Stand-Up Maths] is here with a video taking the viewer through the various movie film formats. He claims it’s the first video shot for YouTube in 35mm, and given that his first point is about the costs involved, we can see why.

In particular it serves as an introduction to the various film terms and aspect ratios. We all know what full frame and IMAX are, but do many of us know what they really mean in camera terms. A particularly neat demonstration comes when he has two cameras side by side with the same stock as a split screen, one 35mm and the other 16mm. The cheaper smaller framed format is good quality, but using a profession resolution chart you can see some of the differences clearly. The full film is below the break, and we’d suggest you watch it in the full 4K resolution if you are able to.

Meanwhile, some of us have been known to dabble in 8mm film, and even sometimes shoot footage with it.

Thanks [Jurjen] for the tip.

[The Thought Emporium] has been fascinated by holograms for a long time, and in all sorts of different ways. His ultimate goal right now is to work up to creating holograms using chocolate, but along the way he’s found another interesting way to manipulate light. Using specialized diffraction gratings, a laser, and a few lines of code, he explores a unique way of projecting hologram-like images on his path to the chocolate hologram.

There’s a lot of background that [The Thought Emporium] has to go through before explaining how this project actually works. Briefly, this is a type of “transmission hologram” that doesn’t use a physical object as a model. Instead, it uses diffraction gratings, which are materials which are shaped to light apart in specific ways. After some discussion he demonstrates creating diffraction gratings using film. Certain diffraction patterns, including blocking all of the light source, can actually be used as a lens as the light bends around the blockage into the center of the shadow where there can be focal points. From there, a special diffraction lens can be built.

The diffraction lens can be shaped into any pattern with a small amount of computer code to compute the diffraction pattern for a given image. Then it’s transferred to film and when a laser is pointed at it, the image appears on the projected surface. Diffraction gratings like these have a number of other uses as well; the video also shows a specific pattern being used to focus a telescope for astrophotography, and a few others in the past have used them to create the illusive holographic chocolate that [The Thought Emporium] is working towards.

It isn’t just a spy movie trope: secret messages often show up as microdots. [The Thought Emporium] explores the history of microdots and even made a few, which turned out to be — to quote the video you can see below — “both easier than you might think, and yet also harder in other ways.”

If you want to hide a secret message, you really have two problems. The first is actually encoding the message so only the recipient can read it. However, in many cases, you also want the existence of the message to be secret. After all, if an enemy spy sees you with a folder of encrypted documents, your cover is blown even if they don’t know what the documents say.

Today, steganography techniques let you hide messages in innocent-looking images or data files. However, for many years, microdots were the gold standard for hiding secret messages and clandestine photographs. The microdots are typically no bigger than a millimeter to make them easy to hide in plain sight.

The idea behind microdots is simple. They are essentially tiny pieces of film that require magnification to read. After all, you can take a picture of the beach and shrink it down to a relatively small negative, so why not a document?

The example microdots use ISO 50 film to ensure a fine grain pattern, although microfilm made for the task might have been a better choice. Apparently, real spies used special film that uses aniline dyes to avoid problems with film grain.

However you do it, you need a way to take high-resolution images, put them on film, and then trim the film down, ready to hide. While microdots were put on pigeons as early as 1870, it was 1925 before technology allowed microdots to hold a page in only ten square microns  in a 10×10 micron square. This was a two-step process, so between the film and the single-step processing, these homemade microdots won’t be that dense.

If all this is too much trouble, there’s always invisible ink. Or use a more modern technique.

Edwin Land, were he alive, would hate this post. He wanted to be known for this scientific work and not for his personal life. In fact, upon his death, he ordered the destruction of all his personal papers. However, Land was, by our definition, a hacker, and while you probably correctly associate him with the Polaroid camera, that turns out to be only part of the story.

It was obvious that Land was intelligent and inquisitive from an early age. At six, he blew all the fuses in the house. He was known for taking apart clocks and appliances. When his father forbade him from tearing apart a phonograph, he reportedly replied that nothing would deter him from conducting an experiment. We imagine many Hackaday readers have similar childhood stories.

Optics

He was interested in optics, and at around age 13, he became interested in using polarized light to reduce headlight glare. The problem was that one of the best polarizing crystals known — herapathite — was difficult to create in a large size. Herapathite is a crystalline form of iodoquinine sulfate studied in the 1800s by William Herapath, who was unable to grow large sizes of the crystal. Interestingly, one of Herapath’s students noticed the crystals formed when adding iodine to urine from dogs that were given quinine.

Land spent a year at Harvard studying physics, but he left and moved to New York. He continued trying to develop a way to make large, practical, light-polarizing crystals. At night, he would sneak into labs at Columbia University to conduct experiments.

His breakthrough was the realization that he could develop tiny polarizing crystals and put millions of them in a film to form a large polarizer without the problem of growing giant crystals. At first, he created tiny crystals, suspended them in liquid, and aligned them with an electromagnet. A sheet of celluloid would pass through the liquid, picking up precisely aligned microcrystals. When the liquid dried, the crystals remained, and you had a sheet of polarizing film.

A Polarizing Patent

That was the basis of the 1929 patent for polarizing films. Later, the process changed to using a polymer sheet with crystals that aligned by stretching the plastic without an electromagnet. Eventually, the crystals would be made of iodine. Not only did polarizing filters reduce glare, but using two of them allowed you to control the flow of light. If the two filters have the same alignment, light with the correct polarization will pass. As you rotate one filter, less light will pass until the polarizers are at right angles to each other. At that point, virtually no light will flow. Polariscopes can even detect stress in glass objects.

In 1932, a Havard professor who had family money joined with Land to form Land-Wheelwright Laboratories to manufacture polarizing films. You’d think that wouldn’t be a big business, but it turns out there were many uses for a large polarizer, although auto headlights didn’t work out. Kodak bought polarizing film for movie cameras. American Optical made polarized sunglasses. It even made 3D movies and photographs more practical.

In 1937, the company changed its name to Polaroid. But it would be 1943 before the Polaroid camera was even an idea. Of course, between those years, there was a World War to contend with.

The company sold many 3D movie cameras. They produced a 3D film for the 1939 World’s Fair. Unfortunately, the right eye film has been lost, but the left eye one is still around, and you can see it below.

War Years

Turns out polarizing films have more military uses than you might guess. Pilots and soldiers benefit from polarized goggles. A 1944 magazine article noted that all fire control teams had polarizing goggles that could adjust their darkness by turning a knob. Polaroid even produced goggles for war dogs and mules. Even General George Patton was seen sporting a pair of Polaroid goggles.

While most of the company’s war effort was optical in nature, it wasn’t all polarized light technology. For example, the company also developed synthetic quinine after the war shut off the supply of tree bark normally used to produce the medicine. While that might seem odd, at the time, quinine crystals were used in the polarizing films produced by the company. The work ultimately didn’t pan out for practical purposes, but it did win the Polaroid researcher responsible a Nobel Prize in 1965, as it was a landmark achievement in organic chemistry.

Before the war, a Polaroid employee made the Vectograph, a stereo viewer that encoded depth information in the form of polarization. During the war, the technique was used to enhance reconnaissance photos. Land and his company also played important roles in future photo intelligence development. He contributed to the U2’s camera and several satellite- and balloon-borne cameras.

The Camera

Of course, what Land is really known for is instant photography. Inspiration struck in 1943 while on vacation in Santa Fe, New Mexico. He took a picture of his three-year-old daughter. She wanted to see the resulting picture right away.

That wasn’t possible, of course, but it got Land thinking. Reportedly, in an hour, he had the basic ideas in place to make the system work. Within three years, he had a prototype. Two years after that, the camera was on sale to the public.

The camera used a technique known as diffusion transfer that was known before Land used it and made it practical for cameras. Prior to this, it was used to copy documents and produce lithography plates before being replaced with more modern techniques.  The company made 60 cameras and put 57 of them on a shelf in a department store, thinking they would have some time to make more. The cameras were all sold in a single day, as you can see in the video below. Later, a demonstration by Steve Allen on national television undoubtedly sold many cameras.

The secret isn’t so much in the camera as in the film. In the original process, silver halide — just like regular film — turns black where the light hits it and doesn’t blacken where the image was dark. A dye transfer process migrates dye to the surface of the picture, being blocked where the image is black. This produces a positive image. This requires a series of chemical reactions.

To start the reactions, the reagents are lumped together at the edge of the picture. Rollers in the camera crush capsules containing the reagents and spread them across the picture. For color photos, there are multiple light-sensitive layers and complementary dyes.

In early cameras, the development occurred in the middle of a pack, and after a delay, the user had to separate the image from the rest of the pack. However, in 1972, integral film appeared, which used more chemical magic to develop the image right in front of your eyes.

Genius

Now, when you hear of Edwin Land, you know he did more than invent the instant camera. Not bad for someone who dropped out of school twice. He did, eventually, get an honorary PhD from Harvard. In fact, Harvard’s Baker Library has a great exhibit about Land and his work if you want a lot more detail.

If you have an instant camera, you can build your own film packs. Despite digital photography, we are still fascinated with these instant cameras.

We’re now somewhere over two decades since the mass adoption of digital photography made chemical film obsolete in a very short time, but the older technology remains in use by artists and enthusiasts. There’s no longer a speedy developing service at you local mall though, so unless you don’t mind waiting for one of the few remaining professional labs you’ll be doing it yourself. Black-and-white is relatively straightforward, but colour is another matter. [Jason Koebler] has set up his own colour processing lab, and takes us through the difficult and sometimes frustrating process.

From an exhaustive list of everything required, to a description of the ups and downs of loading a Patterson tank and the vagiuaries of developer chemicals, we certainly recognise quite a bit of his efforts from the Hackaday black-and-white lab. But this is 2024 so there’s a step from days past that’s missing. We no longer print our photos, instead we scan the negatives and process then digitally, and it’s here that some of the good advice lies.

What this piece shows us is that colour developing is certainly achievable even if the results in a home lab can be variable. If you’re up for trying it, you can always automate some of the process.