Before the days of LCD displays, the only way you could keep track of what speed film you had in your camera was to remember it, select a dial on the camera, or cut out a piece of the film box and place it in a designated area on the back of the camera.

However, not all cameras have ISO dials or places to put a note; and even if they do, some have a limited range of ISO labels to choose from. To remedy this problem, photographer Guy Sie customized a set of 3D-printed hotshoe covers with common ISO ratings on the top so you can easily check what speed film you have inside your camera.

"On my fully manual '50s Leica M3 rangefinder camera, the ISO film speed indicator dial on the back only goes up to 200 - the fastest speed available at the time. With film speeds going up to ISO 3200 now the dial is basically useless so I don't bother with it, but then I have to remember what film I loaded last time I used the camera - which might be weeks ago," says Sie in the project summary. "After screwing this up a few times too many, I modified gcardinal's hotshoe covers by adding ISO speed numbers to the top. Load your camera, swap out the cover for the right ISO, and never forget what film is loaded again!"

The set consists of covers for ISO 100, 125, 160, 200, 320, 400, 800, 1600, and 3200 film stocks. As is, the numbers on the covers are raised, but if you really want to make them pop, you can give them a little coat of paint or black them out with a permanent marker, as Sie has done with the set he made for his Leica M3.

The files for Sie's hotshoe covers are free to download through Thingaverse. You can print out at home if you have a 3D printer on hand or pay a few dollars to have some made through online print shops like Shapeways or Sculpteo.