I was just shooting out in the snow with my F-1N and pre-S.C. 50/1.4, and a better hood would have helped. I was using the Canon BS-55 hood. I read somewhere, perhaps here on APUG, that a certain square hood works well with Canon FD lenses. Any recommendations? I would be using the hood primarily with the 50/1.4 mentioned above and my 55/1.2 S.S.C. It would be nice if it could also cover my FDn 35/2 and FDn 100/2.8.
You could use something like a Lee compendium hood, if you really wanted the most effective hood.
In reality, though, when you're shooting in the snow, most of the flare comes from the subject itself, so you would be better off with a later multicoated lens.
You could also make and test a rectangular mask for the front of the BS-55. With the bayonet mount it can properly register itself when you re-mount it.
I use a high-quality multicoated filter (Hoya HMC) in conjunction with the BS-55. I am actually more concerned about keeping snowflakes and other such mositure off of the filter. This tends to ruin a shot. I had to keep my hand in front of the hood while I waited for my subject to arrive.
A multicoated filter will reduce reflections between the filter and the front element of the lens, but it does not reduce reflections between the glass-air surfaces within the lens, and that is a source of veiling flare from light that is actually part of the image. Multicoating within the lens reduces that flare and improves overall contrast.
I have one of these lenses and a B S 55 Hood and you're problem is about par for the course for this lens even with the correct hood, I corrected the problem by buying the later 50mm f1.4 FDn lens which is multi-coated , as David writes the multi coated filter won't prevent the internal reflections within the optic. Please note, none of the Canon FD 50mm f1.8 lenses either old or new are multi coated, but single Spectra Coated http://www.mir.com.my/rb/photography/companies/canon/fdresources/fdlenses/50mm.htm#f1.8
The cheapest but not so nice fix, is to use the light cardboard from a biscuit packet, use a black felt pen to darken the inside and duct tape on the outside to hold it to the outside.
Another fix is to use a longer lens hood with the same filter ring.
I use a hood designed for an 85mm lens on one of my 50mm lens in bad weather.
A 100% viewfinder is good here to check for vignetting.