P#6 Q#1a: Why Is a Light Meter Useless When Photographing Fireworks -- Or Photographing More Generally at Night?

Don't use a light meter when you're shooting at night

Jim Zuckerman: Well, it's a really good question. The answer is this: Meters are designed or programmed to give you a correct meter reading when it detects middle tone, middle gray.

Ansel Adams called it zone five. Middle gray basically means it's the midpoint between black and white.

When a light meter sees that, it's designed to give you a correct exposure. So if a meter sees, let's say, a snowfield -- you're in winter, it's snowing, the sky is white, and the ground is white. The meter looks at that and says, "Oh, middle gray," and it gives you an exposure to give you middle tones in that situation which means the snow will be underexposed.

The same thing happens when you photograph at night. If you composed the moon, let's say, the moon is going to be a fairly small part of the composition unless you've got a 2000mm lens which we all don't.

When the meter sees all that night sky, it goes, "Oh, middle gray," and it makes the picture too light, trying to make that black sky gray. What happens to the moon when it's too light is it washes out -- it becomes a white disk. So you can't use the light meter. There's just no way around it.

Audri Lanford: And how about at twilight?

Jim Zuckerman: The same is true for twilight. When you shoot at twilight, there's a certain time to do it -- not time on the clock because it depends upon the latitude on the planet that you happen to be shooting, and also the season. It gets dark in the summer later, and so on.

When you shoot twilight correctly, if you want to get that real deep cobalt blue sky which is so beautiful, you shoot that just before dark.

Some people make the mistake of shooting too early when it's too light, and they shoot at a time that is considered to be dusk. Dusk is when the sky is still fairly light, but some of the city's lights start to come on.

That's too early. At that time, you can use your light meter.

But when it gets darker and you're just ten minutes before the sky is black, that's the window of opportunity.

At that time, the same thing happens to the meter as at night -- it wants to make it middle gray, so it wants to make the scene much lighter than you want it to be, so you can't use the light meter.

To summarize

You're better off not relying on a light meter when shooting at night or at twilight. The meter will read the light incorrectly, and your photographs will be under or over exposed. This certainly applies to fireworks, as you'll see later in this interview.