For camera metering, you are supposed to set that lens to 32 and then lock it with the little tab down by 4.5 that slides between white and orange. Make sure that is done first. It should look just like the photo below.
Now, if it is still dark when you're at 32, it could mean there is something wrong with the little tab. Most lens are designed to keep the aperture blades open when you are focusing and looking through the lens. Only when you take the photo is the lens given a physical command to close the aperture blades to the correct settings for that photo.
In your case, the blades are closing when you stop down (move toward 32) the lens. That shouldn't happen. The blades should stay open until the very moment you take the photo.
The little lever that holds the blades open is only visible when the lens is off the camera. Take off the lens, and you should see a rectangular metal tab sticking out to the right of the electrical contacts and to the right of the 4.5 aperture mark. (You can see it on top in the pic below.) You should be able to physically move that tab sideways with your fingers, and you should see and feel the aperture blades open and close when you do. Make sure that action is nice and smooth. If the blades are not being help open, that explains why it gets dark when you make the aperture smaller.
