Tiffen ND (Neutral Density) filters reduce the amount of light entering the lens without affecting color balance. The ND 3, 6, and 9 filters represent different levels of light reduction:
- **ND 3**: Reduces light by 1 stop, suitable for slightly overexposed conditions.
- **ND 6**: Reduces light by 2 stops, useful for medium exposure control.
- **ND 9**: Reduces light by 3 stops, ideal for very bright conditions or to achieve slow shutter speeds.
- These filters are commonly used to control exposure, achieve shallow depth of field, and create motion blur effects.