Honestly, we never wondered how those old film cameras used to put the date stamp in the lower right-hand corner of the frame. Luckily, [Ben Krasnow] does not suffer from this deplorable lack of curiosity, and his video teardown of a date-stamping film camera back (embedded below) not only answers the question, but provides a useful lesson in value engineering.
For the likely fair fraction of the audience who has never taken a photo on film before, cheap 35-mm cameras were once a big thing. They were really all one had for family snapshots and the like unless you wanted to invest in single-lens reflex cameras and all the lenses and accessories. They were miles better than earlier cartridge cameras like the 110 or – shudder – Disc film, and the cameras started getting some neat electronic features too. One was the little red-orange date stamp, which from the color we – and [Ben] assumed was some sort of LED pressed up against the film, but it ends up being much cooler than that.
Digging into the back of an old camera, [Ben] found that there’s actually a tiny projector that uses a mirror to fold the optical path between the film and a grain-of-wheat incandescent bulb. An LCD filter sits in the optical path, but because it’s not exactly on the plane of the film, it actually has to project the image onto the film. The incandescent bulb acts as a point source and the mirror makes the optical path long enough that the date stamp image appears sharp on the film. It’s cheap, readily adapted to other cameras, and reliable.
Teardowns like this aren’t fodder for [Ben]’s usual video fare, which tends more toward homemade CT scanners and Apollo-grade electroluminescent displays, but this was informative and interesting, too.
Thanks for the tip, [Jan].
The orange color does not created by the Film itself (it is a negative). On the Film there is the datecode blueish-green.
The color is produced by the tiny light-bulb and the relative long time by heating up and cool down the Wolfram wire in the bulb.
:)
If anyone is still using film camera and likes date/time stamp, theoretically one can have different color. As film is negative, you need to find LED of opposite color. Want red stamp? Look for cyan LED. Want something close to purple (Magenta), get green LED.
Pretty sure that if that were the case, photos would come out inverted. All of the film developers I have dealt with take the negatives and then invert the image again so the print comes in positive…
The negatives as their name implies have their colors inverted. When scanning digitally then yes of course you have to invert the colors again in software to make them correct, but if exposing the negatives and using a chemical photo development process light is shown through them onto the photo paper which is then developed and set in a bath and this process inverts the image yet again.
*shone … gah stupid autocorrect and lack of an edit button for had comments!!!
Uh … photographic process inverts the color twice. Hence why there are negatives and positives made from those negatives.