Neutral Density filter with optical density 0.3, reducing light by one stop (ND2), allowing wider apertures or slower shutter speeds in bright conditions.
Optical Density and Aperture Value
The ND 0.3 filter (also known as ND2) has an optical density of 0.3 and reduces incoming light by exactly one stop. This means the amount of light is halved. One stop corresponds to a doubling or halving of the amount of light.
The ND2 designation system indicates: The number specifies the factor by which the light is reduced. ND2 therefore means: light is divided by 2.
Typical Applications
Daylight Filming at Wide Apertures
The ND 0.3 is ideal for situations where you want to shoot with a wide aperture like f/1.4 to f/2.8, but the daylight is too bright. With the filter, you can continue to use your preferred wide aperture in such conditions.
Motion Blur and the 180-Degree Shutter Rule
To adhere to the 180-degree shutter rule (the shutter angle should be 180 degrees, which corresponds to a shutter speed of approximately 1/50 second at 25p), you often need light reduction. The ND 0.3 enables this in moderate lighting conditions without having to stop down too much.
Subtle Brightness Adjustment
The ND 0.3 is perfect when you only need a small adjustment. On cloudy days or in situations with reflected light, only a one-stop reduction is often necessary.
Difference from Variable ND Filters
Variable ND filters allow for stepless adjustment of optical density between different values (typically ND2 to ND400 or similar). The fixed ND 0.3 filter, on the other hand, offers:
- More stable optical quality: No color cast due to internal construction
- Higher light transmission: Fewer internal reflections in a specialized filter
- More affordable price: Fixed filters cost less
- Simplicity: No adjustment possible, which prevents errors
Variable ND filters are more flexible but can lead to color casts or moiré effects at strong settings.
Relation to the 180-Degree Shutter Rule
The 180-degree shutter rule is fundamental for natural-looking motion blur in film production. At 25 frames per second, the shutter angle should be 180 degrees, which corresponds to a shutter speed of 1/50 second.
In bright daylight, this is often impossible without stopping down, because:
- ISO is usually set to the lowest value (often 100 or 200)
- The aperture can only be closed down to a certain point
- The shutter speed is fixed by the rule
The ND 0.3 filter helps to adhere to this rule while preserving a creatively chosen aperture.
Specifications
- Optical Density: 0.3
- Light Loss: 1 stop
- Multiplier: ND2
- Typical Transmission Rate: 50%