Neutral Density Filter
Information
Filter Factors
Neutral Density filters are often overlooked by beginning photographers in
favor of special effects filters like the star or diffusion. ND filters have multiple
uses. They allow you to lengthen exposure time and create the white foaming
water seen in landscape photos to give a feeling of motion. When shooting slide film,
Graduated ND filters are the professional's tool. They allow the photographer to
preserve detail in the shadows and "mid tones" without blowing the
highlights out.
There is nothing mysterious about filter factors. A factor of 2 simply means that you
need twice as much light with the filter mounted on the lens for the exposure. You
can open your lens 1 stop (one change in f number equals twice the light) or set your
shutter speed for twice the amount of time.
ND2 = 1 stop less exposure
ND4 = 2 stops less exposure
ND 8 = 3 stops less exposure
Some filter manufacturers use an optical density numbering system on their Neutral
Density Filters. Tiffen is one of them. This can be confusing to someone that is used to
working with the more common 2X , 4X filter factor systems.
This chart shows the exposure values.
| Filter marked as |
Multiply exposure by: |
Or, open lens in stops |
| ND .1 |
1.25 |
1/3 |
| ND .2 |
1.6 |
2/3 |
| ND .3 |
2 |
1 |
| ND .4 |
2.5 |
1 1/3 |
| ND .5 |
3.1 |
1 2/3 |
| ND .6 |
4 |
2 |
| ND .8 |
6.25 |
2 2/3 |
| ND .9 |
8 |
3 |
| ND 1.0 |
10 |
3 1/3 |
|
