built in filters
when super 8 film first came out, it was all tungsten balanced. so if you shot your film in daylight you'd need to use an orange 85 filter to counteract the comparative blueness of daylight. you don't need to buy a filter - (almost) all super 8 cameras have a little one built in behind the lens.
when shooting either vision3 200t or vision3 500t (the t stands for tungsten) in daylight you need to make sure that the filter is engaged.
most cameras have a switch or a key to remove the filter.
the switches commonly have 2 symbols like this:
when your switch is set to the sun, for shooting in daylight, the filter is inserted behind the lens. when the switch is set to the lightbulb symbol, for shooting in tungsten light, the filter is removed.
keys are usually inserted into a slot in the top of your camera and often look like this:
when the key is inserted the filter is removed.
unfortunately this is complicated by the fact that many camera automatically remove the filter if the cartridge doesn't have a special notch in the side. it's much easier to show this in a video than in text, so please have a look at this gr8 explanation from pro8mm: http://vimeo.com/10132030
n.b. a vision3 200t cartridge does have a filter notch, but 500t does not.
ektachrome 100d is daylight balanced (hence the d), so you need to make sure that the 85 filter is removed for shooting in daylight. if your camera has a little switch inside the film compartment to read filter notches, this will happen automatically, otherwise remove the filter using the switch or key.
to colour balance 100d under tungsten light you need to use an 80 blue filter. there are no circumstances in which you'd want to leave the 85 filter in when shooting 100d.
tri-x is black and white, so needs no colour balancing - hooray. technically you should always shoot with the filter removed but it's no big deal if the filter stays in. we think it might even increase the contrast a little.
external filters
it's also possible to use external filters - some more hardcore super 8 users like to do this as the internal filters, which are plastic, can compromise image quality a tiny bit. you can buy or order the correct filters from most photographic shops, then just remove the internal filter and screw the external one onto the end of your lens.