What does a neutral density filter do ?
Used primarily for photomicrography and video microscopy, the ND filter helps camera sensors from being overpowered and therefore reproduce more realistic or dynamic colors.
My microscope came with a blue filter, what is it used for?
These filters should not be used with "daylight color" film as Kodak Filter 80A and other "conversion filters" are designed to work with companion films or imaging platforms.
A green filter was included with my microscope, why would I use that ?
GIF's or Green Interference Filters look somewhat yellowish in appearance, are more expensive but deliver the best green light imaging at 546nm for phase contrast work.
Also, the human eye sees the green spectrum the best.