Do I have to hold down the B door of the mechanical film camera? Can you press release and then press it again to end the exposure? If you want to keep

Only press the shutter to open the door B, and release the shutter to close the door B.. Some cameras have a door T, which can be opened by pressing it once and closed by pressing it again.

In order to solve this situation, mechanical cable release can be used to shoot. Press the shutter with the cable release device and lock the cable release device with the screw. When you need to close the shutter, loosen the screw and the shutter will close. This is just a mechanical cable release. It's all secondhand, so it's hard to buy it now.