Checking the operation of your camera on tour is advisable A fully manual mechanical camera can be fully checked as per the procedure written below. This will not work on many automated electronic cameras. You may need a modified procedure.
The metering system
The metering system can be very easily checked during the daytime. Point your camera into the clear blue sky during the middle of the day on a sunny day. Point the lens high in the sky but well away from the sun. Set the aperture to 16 and take a reading of shutter speed. The shutter speed indicated should be the nearest speed that has the same number as the ASA. Eg if you have 400ASA film the camera should indicate 1/500 second, 100 ASA -> 1/125 second etc. If you take the reading through a window make sure the window is not tinted or this will change the calibration. If the setting is very wrong, first recheck that you have done this correctly. Then adjust the meter sensitivity away from what appears to be the correct reading. On older cameras change the ISO setting until the meter gives the correct reading; on modern electronic cameras adjust the exposure compensation function (refer to your camera manual) until the camera gives you the correct setting.
Shutter mechanisms may partly fail without any warning. Listen to the one second shutter speed. Does the spring drive sound smooth if the camera is mechanical one. If your watch has a stopwatch, time it. It should time to 1.2 or 1.3 seconds. 1 second for the shutter and 0.2-0.3 seconds for your reaction time. Listen to all the shutter speeds down to 1/15 second, do they sound half as long each time? Open the back of the camera, stop the iris to 11. Look through the camera back and through the lens as you fire the shutter. Does the apparent brightness through the lens seem to diminish in regular steps as you go to faster and faster shutter speeds.
Aperture iris blades
Stop the lens completely down. Fire the shutter at each shutter speed and make sure the iris stops down the same amount each time. Look through the shutter from the back of the camera as you do this.
Remove the lens. Place a piece of thin paper over the film plane. Set the camera to the sync speed. Fire the shutter with flash aimed at a reflective surface. You should see the entire area of the shutter area light up on the paper. If it does the flash sync is working.