HOW measure light / aperture with an adapter?

Hi

i recently purchased an adaptall to mount my tamron screw mount telephoto lense to my pentax k1000 bayonet mount camera. it works fine. but i have one problem...

how on earth do u figure out what apperture you need / how much light there is?

once the lens and adaptall are mounted the light meter will move up and down however it DOES NOT vary according to the aperture as set on the lense!

how do i work out what apperture is required?

the note that came with the adaptall reads:

"the automatic diaphragm of the lens will not function, so meter reading must be made with the lens apperture stopped down."

what does this mean?

can anyone please help me? i am in desperate need for quick help as am leaving on an overseas holiday in 6 weeks and i want to take some good photography!

thank you for any advice you can give me! PLEASE HELP!

cheers

OzSheppy

Hi,
With the Pentax type screw mount lenses, there is an Auto/Man switch. On Auto the camera stops the lens down just before the photo is taken so the iris will not move when you move the aperture ring. With the switch set to Man, the iris will move. As they is no coupling on your adapter you must make sure the lens is set to Man. You should notice that the picture will get daker as you move the aperture dial.

Regards
Kim