According to some web searches I did, Pentax SF1n is an auto exposure capable SLR camera. If that is the case, I'd suggest setting camera's ISO to match the film. (that would be 400) Then set the camera to aperture priority mode, which would be "A", or in program mode "P" first. Then, set the aperture somewhere that will keep your shutter speed above 1/60s or so. Once this is done, camera itself will measure the amount of light available and set the shutter speed automatically.

EF+- probably is exposure compensation. Don't mess with those, yet. Keep it at zero. It has nothing to do with contrast.

I think what's in order is to find and download a manual for this camera, setup all the knobs and stuff to default setting, then do some test shoot. For all we know, it's possible that camera may be in some strange mode or setup. Most camera manuals do tell you where the setting should be set to, to start shooting.

I'd suggest doing this without a flash as it will add another element to consider.

Assuming everything is working as it should, the camera should expose your film correctly most of the time. If it doesn't you got a problem....