Using fully manual lenses?

[Don Simon]

I was hoping someone could help me with this kinda newbie question. I recently got the prints back from a roll of film that included some shots taken with a 500mm lens which is fully manual (i.e. as well as the aperture ring there is an Open/Close ring to manually close the aperture; the aperture is not automatically closed). I only took a couple of shots with the lens, but in both cases I forgot to close the aperture. Stupid I know; I was preoccupied with trying to image steady, even with a tripod! I composed the shot, pressed the shutter button halfway (so the TTL meter suggested an appropriate shutter speed), set the shutter speed and took the shot. The resulting photos were correctly exposed (if rather lacking in tonal range). I assume this is because the TTL meter correctly metered the light through the lens with the aperture wide open as if on the lowest/widest aperture setting. My question is, in order to meter with a smaller aperture, do I simply set aperture, manually close it down and then meter? Also if I'd rather use a handheld meter (which is quite a lot of the time), should I go about it as if I were using say a 50mm lens, or do I need to make variations to account for the length of the lens?

Sorry if these are stupid questions - previously I've never used any lens over 250, and I've never used a lens that requires you to close the aperture yourself, so I'm on unfamiliar territory here. Thanks! :hail: