Silverbased

Well—possibly.

Reading a recent Einstein biography, I was most amused to learn this little tidbit: In 1936, Einstein and an associate named Gustav Bucky were issued US Patent No. 2,058,562 for a “Light Intensity Self-Adjusting Camera.”

Albert Einstein, overexposed in 1934

The text of Einstein & Bucky’s patent can be seen here, and the accompanying diagram here.

This date is quite early for such radical technology: The earliest auto-exposure camera I know about which actually reached the marketplace was Bell & Howell’s Electric Eye 127, circa 1959. But I’m not sure Einstein’s design was really the first invention of an auto-exposure camera (and I don’t have the patience to research all the patent literature).

If you’re having a little trouble deciphering the patent documents, the basic idea is this: the upper lens aims light from the scene onto a photoelectric cell. This is wired to a meter movement, which deflects through larger angles as the light level increases.

But instead of the usual read-out pointer, the axis of the meter connects to a pie-wedge shape of clear sheet; this has a graduated neutral-density filter along its bottom arc. The arc swings across the light path of the lower, picture-taking lens. Brighter light levels move the denser end of the filter into the light path, keeping the exposure consistent.

You may remember that Einstein himself started out as a Swiss patent examiner. And, I don’t want to be too hard on the father of General Relativity, a Nobel Prize winner, and a certified genius. But there are a couple of problems with this scheme.

Using a neutral-density filter means throwing light away. This would not have been good news in 1936. Kodak’s then-new Kodachrome had a speed of about 8 (expressed in modern ISO terms—the scale did not exist then). So adding a filter would necessitate longer exposures and wider lens apertures—sacrificing depth of field, and increasing aberrations.

Perhaps recognizing the problem, the patent includes a second system of manual aperture stops. These are coupled so that smaller lens apertures also admit less light to the meter cell. However this seems like an afterthought—it brings back complicated manual intervention to a system that was supposed to be automatic.

Another consideration for today’s photo-geeks is whether the gradient filter would do strange things to bokeh—e.g., causing out-of-focus highlights to have an odd “fade-out” across them.

The obvious question to ask is why Einstein and Bucky didn’t make the next logical leap: Directly controlling an iris using the movement of the light meter. This was Bell & Howell’s approach, albeit with a very simplified aperture formed by two crossing, comet-shaped openings. Even then, inertia of the moving parts slowed its response time.

Ultimately the breakthrough for mechanical auto-exposure cameras was the “trapped needle” system, used in countless 1960s and 1970s Japanese 35mm models.

A light meter needle (which could provide an exposure preview in the viewfinder) is pinched and immobilized as the the shutter button button is pressed. The photographer’s finger pressure also closes down the lens aperture from its widest opening; but the needle position limits its travel, halting it at the correct f/stop.

Aside from requiring a long stroke of the shutter release plunger, the system was simple and reliable. But to the best of my knowledge, no Nobel Prizes were ever awarded.

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Postscript: A bit more research reveals that the very first auto-exposure still camera ever marketed was Kodak’s “Super Six-20” from 1938. It’s seen at the bottom of this column by the sadly-just-deceased Burt Keppler. Evidently Kodak sold fewer than 800—so I don’t feel too guilty for being unaware of it. Interestingly Kodak seems to have used a version of the trapped needle design I described above, as discussed in the “Notes” section of this George Eastman House catalog entry.

I was looking over some creaky old folding cameras recently—probably about 90 years old—and was amused by a curious fact: A couple of them used a film size you can still buy today.

Now, perforated 35mm film has existed ever since it emerged from Thomas Edison’s lab as a movie stock in 1892. (William Dickson is credited with the actual invention.) But only in the 1920s, after the Leica camera, did 35mm gain wide acceptance as a still-camera film.

Even then, bulk cine film had to be re-wound into special film cassettes that were proprietary to particular camera brands. Finally, in 1934 Eastman Kodak introduced the Retina camera, along with a new disposable metal film cassette preloaded with 35mm film. In keeping with Kodak’s other three-digit film designations, the new format was called “135.”

My father’s 1937 Retina: 3rd version, three years after the introduction of 135 film

Cleverly, Kodak’s German division (the former August Nagel cameraworks) designed the cassette to be backwards-compatible with Leica and Contax cameras, as well as the new Retina line. Thanks to the popularity of the Leica and the Retina—and perhaps even more so, the affordable Argus—the 135 cassette was a success. Today, it’s the universally-known way to shoot 35mm film (ignoring oddities like 250-exposure backs for motor-drive cameras).

Yet this is not the oldest still-camera format we continue to use today. That distinction belongs to 120 film.

Kodak introduced the “No. 2 Brownie Camera” in 1901, a simple $2.00 box camera designed to shoot images 2-1/4″x 3-1/4″*. And for this camera, Kodak introduced a new film size, 120.

The earliest spools had wooden cores (this one is from Ansco, who used the designations 4A or B2 for the size), later metal, and finally plastic. But the dimensions of these three spools are the same.

As time went on, 120 was adopted by a wide range of camera styles: From simple snapshooters to the fine Rolleiflex (introduced 1929) and Hasselblad (introduced 1948). Its use in these professional-level cameras helped keep demand for the format strong; so today it remains the most widely-available film size after 35mm.

I need to get on my soapbox for one brief rant: Please, please, please, don’t mistakenly call this size “120mm.” Even B&H’s online store has been known to get this wrong. The film is actually about 63mm wide, and the 120 is just an arbitrary number from the dim mists of Kodak history.

Originally Kodak’s three-digit size designations were supposed to have some meaning: but the rationales were rather obscure, and soon became unworkable as new sizes appeared. In any case, Kodak continued to give new film formats various three-digit monikers, like 127 for “Vest Pocket” camera rollfilm or 828 for “Bantam” size—right up through 110, the drop-in plastic cartridges introduced with the Pocket Instamatic series in 1972.

Today, the roadside of photo history is littered with the carcasses of extinct film formats. The once-common 116 and 616 sizes are gone, and so are 620 and 828. “Vest Pocket” 127 limps along with a single Croatian emulsion still available. Users of 126 Instamatics must scour the internet for the last sources of film.

Yet even at 107 years old, the 120 film format still seems to be going strong.

*Today we might call this “6×9 cm,” although that’s only approximate: the actual negative is more like 5.6 x 8.2 cm.