Filter factor calculator
Turn a filter factor into stops of extra exposure and a corrected shutter speed.
About this tool
Contrast and ND filters absorb light, so your exposure must increase by the filter's factor. This tool lets you pick a lens filter such as yellow, orange, red, or ND and enter your metered shutter, then returns the extra stops needed and the corrected shutter speed. It keeps black-and-white and long-exposure frames properly exposed.
How to use it
- Select the filter you are using, for example yellow, orange, red, or an ND.
- Enter the shutter speed your meter suggests without the filter.
- Read the extra stops of exposure the filter requires.
- Set the corrected, slower shutter speed the tool returns.
FAQ
What is a filter factor?
It is how many times more light the exposure needs. A factor of 2 means one extra stop, and a factor of 4 means two extra stops.
Do cameras with through-the-lens meters still need this?
TTL meters usually compensate automatically because they read light after the filter. This tool is most useful with handheld meters or unmetered cameras.