I would like to know the following regarding filters in general and in relation to dv/hd cameras with a 35mm adapter.

Polarizer
- How many f-stops does it lose?
- Other than using it to reduce reflections on surfaces such as water, glass, etc....what can it be used for and its effects?

85
- Do you need an 85 if you're working on video when you can manually adjust the tungsten/daylight/white balance? Is there a benefit if you use the 85 instead of manipulating the tungsten/daylight/white balance?

ND (not talking about grad ND)
- With a 35mm adapter on, should the internal ND be used or it's best to use an external one? Advantage/disadvantage of using the internal ND?

Other:
- I know what will happen if you shoot tungsten film for day exteriors without an 85. What happens if you put in an 80A instead?

Thanks.

Polarizers usually lose at least 1 stop. You have to check the specs of the brand of the particular filter you are considering.

-- They also deepen the blue of the sky perpendicular to the sun's axis. IOW, if the sun is directly overhead, the sky at the horizon will be darker.

-- Water can be bluer or even greener from some angles.

-- Colors of foliage and to some extent other things tend to appear richer, if only becasue the sheen is removed. This can make some foliage look odd, though.

ND filters: I'm not sure what you mean by the 35mm adapter, but if your camera has a built-in ND filter, you should use it first, if for no other reason than to avoid stacking external filters.

Color correcting filters really have no place on video cameras. The cameras compensate for light color by altering the response curve of the CCDs. Only if you wished to force a particular effect would you want to use such filters, in which case you would disregard the white balance altogether.