Photography

ND filters

Neutral density (ND) filters don't change the colors of your pictures, nor do they add visual effects. What do they do, then? They make your picture darker. They look like a transparent gray, so that they don't change your colors. Why would you want your pictures darker, anyway? Let's look at a typical application.

Suppose you're photographing outside, it's a sunny day, and your lightmeter gives you f:8 at 1/250". However, you want to make a portrait with as shallow depth-of-field as possible, so you want a larger aperture. That's possible: f:8 at 1/250", for instance is the same exposure value as f:5.6 at 1/500", or f:4 at 1/1000". You have a nice f:1.4 lens which you want completely open, then you have to compensate for the wide aperture by shortening your exposure time further, to 1/8000". Unfortunately you're working with a central-shutter camera which doesn't go faster than 1/500". So how can you reduce the light further?

This is where the neutral density filter comes in. You need an extra 4 exposure values (from 1/500" to 1/8000"), then the table below commands an ND 1.2 filter.

So ND filters can be used when you want large apertures in a bright environment. The same way they can be used if you want long exposure times, like several seconds, to record motion, and your aperture won't go smaller than f:22.

Neutral Density	Filter factor	Exposure Value Change	Amount of light transmitted	Amount of light blocked
ND 0.1	1.25	1/3	80 %	20 %
ND 0.15	1.5	2/3	70 %	30 %
ND 0.2	1.5	2/3	63 %	37 %
ND 0.3	2	1	50 %	50 %
ND 0.4	2.5	1 1/3	40 %	60 %
ND 0.5	3	1 2/3	32 %	68 %
ND 0.6	4	2	25 %	75 %
ND 0.7	5	2 1/3	20 %	80 %
ND 0.8	6	2 2/3	16 %	84 %
ND 0.9	8	3	13 %	87 %
ND 1	10	3 1/3	10 %	90 %
ND 1.2	16	4	6.3 %	93.7 %
ND 1.5	32	5	3.2 %	96.8 %
ND 1.8	64	6	1.6 %	98.4 %
ND 2	100	6 2/3	1 %	99 %
ND 3	1000	10	0.1 %	99.9 %
ND 4	10 000	13 1/3	0.01 %	99.99 %
ND 5	100 000	16 2/3	0.001 %	99.999 %
ND 6	1000 000	20	0.0001 %	99.9999 %