Here’s a handy tip to check if your exposure metering is correct on your old car boot SLRs (or at least the reported exposure). Known as the “Sunny 16 Rule” for reasons that will become apparent; head outside on a bright summer’s day when the sun is high in the sky. Set your camera’s aperture to be F16, set the ISO (or ASA) setting as low as possible (100 or 125), and set your shutter speed to be 125.
Next point your camera at an area of lawn or pavement in full sunlight and see what exposure reading is reported. If it’s F11-F16 your camera is accurate. You can repeat this for different shutter speeds, just make sure you set the ASA rating to match (i.e.. ISO 200 at 1/200 or 1/250, ISO 400 at 1/400 or 1/500).
I haven’t discovered how to do this during a cloudy English winter where you can go weeks without catching a glimpse of the sun (I guess I might need a light meter) but let me know or comment below if you have any further tips.