I recently started using the Nikon f and I’m unsure about what settings are supposed to be used with 400 speed film!
Make sure that you understand what settings are influencing image exposure.
Image exposure can be influenced by three settings, but two principles: Either the amount of light that is used to expose the film is varied (aperture and shutter speed) or the sensitivity of film can be changed in order to be able to shoot in very bright or rather dark surroundings. These are the three settings:
1) aperture (how much light is going through the lens). The amount of light that enters the system is doubled, by a step from e.g. f/8 to f/ 5.6, so smaller numbers mean more light. There is a doubeling of light for all the numbers from f/8, f/5.6, f/4, f2.8/, f/2 to f/1.4.
2) Shutter speed - how long is the film exposed to the light source. The shutter speed is often simply denoted with one number, e.g. "100" which means "1/100 second" or 0.01s. So changing the shutter speed form e.g. 200 to 100 will increase the amount of light by a factor of two.
3) Film speed, often denoted with a ISO or ASA number. Changing from an ISO 200 to an ISO 400 film, increases the light sensitivity by a factor of 2. The amount of light does not change.
Typically an exposure meter is used to determine which shutter speed and aperture combination leads to a correct exposure. The exposure meter needs to know, which sensitivity the film is using.
If your camera has a built in exposure meter, set the ISO/ASA Setting to 400. Otherwise you can use an external exposure meter.