A few years ago I got my first DSLR (a Canon EOS 350D), as well as my first tripod. Now I changed my camera to Nikon D90, but kept the tripod. When I first tried to mount my new camera on the old tripod, I got confused — there was no fixation hole on the camera's bottom as the tripod head would presume. Without that, there is nothing to make the camera stay at fixed position at all angles of z-axis (x being left-right, y being up-down, z being forward-backward). Here are the pictures to help you out:
Do I need to get a separate head for my tripod to accommodate my new D90? If not, how would camera stay in its position when the tripod is configured to take vertical or portrait photos?