Light meter know-how

If you are a photographer, you will need to use a light meter sooner or later. Like in studios, when shooting flash, or when shooting outdoors in mixed light. Or for when you want it accurate. Light meters, like my Sekonic L-358, are invaluable.

But light meters are not perfect. They can vary between modes, between measurements, and between light meters. Even between ISO settings, or times of day.

The good news: modern light meters can be calibrated, i.e. adjusted, when necessary. The bad news: this is sometimes a little similar to black magic.

If you doubt your meter’s accuracy, here is what I would suggest you do:

  1. Set your camera to aperture mode, f/5.6, 100 ISO
  2. Filling your entire viewfinder, shoot a grey card, evenly lit by diffuse daylight. Avoid reflections. Avoid standing in the light (d’oh).
  3. Check if the histogram is neutral in color (Red, Green and Blue channels, if you can display those, are equally bright).
  4. Now check if the histogram is in the centre. If not, adjust the exposure using exposure compensation, until it is in the middle.

You should now see something like this on the back of your camera:

If instead you see a histogram like the one below, the image is too dark – use + (plus) exposure compensation:

If you see the type of histogram below here instead, then the image is too light – use “-” (minus) exposure compensation:

So. Done? Now repeat the process until this is right.

Now that you have adjusted the exposure to get the histogram into the centre, read the shutter speed you now achieved.

Now:

  1. Set your light meter to f/5.6 and 100 ISO.
  2. Dome extended, put it on the grey card.
  3. Without blocking the light, measure the light.

If your light meter indicates the same shutter speed as you got on your camera,you are good. If it indicates something else, you may need to calibrate your meter.

On my Sekonix, this is done by pressing ISO1 and ISO2 together while you turn on the meter – and keeping them pressed. You can now adjust the meter, + or – as needed, then repeat your measurement. Repeat this until you see the same time on your meter that you saw on the camera before.

Now, take some shots metered with your meter, in various light intensities and types, and verify that the grey card peak is in the centre for most images.

Like I said, black magic.  But now you know. Bet you were not aware your meter was adjustable!

 

Metering muddles

A word about light meters again – this time, on how to use them.

1. First turn on the meter.

2. Then move the white dome out, not in.

3. Now set the ISO to your camera’s ISO (press ISO and hold it down while turning the dial, until your camera’s ISO is indicated).

4. Now set the metering mode. A modern light meter has two separate modes:

  • Ambient metering (the “sun” symbol at the top left on the display above);
  • Flash metering (the “lightning bolt” symbol on the display above).

If you want to meter available light for a normal available light photo, select the sun (press mode button and turn dial); but for metering flash, where the meter measures brief flashes of light, select the lightning bolt.

Assume for today’s post, that you only have flash light to worry about in your shot. So you set the mode to flash, and set the shutter speed to your camera’s shutter speed. Set the camera to 1/125th sec, and set the meter to this time as well.

Now when the camera measures, since you have told it your camera’s shutter and ISO, when it measures the light it will tell you the aperture to set the camera to. (After all, exposure is a triangle of “ISO – Aperture – Shutter”.)

5.  Now hold the meter where the subject will be, and aim the white dome at the camera.

6. Now press the big “reset/test” button on the side. The aperture now reads “0”.

7. Finally, fire your flash.

The meter now indicates the aperture you should set set your camera to. If this is different from what you wanted

  • adjust the flash’s power;
  • repeat the procedure, until the meter indicates the aperture you had in mind.

This is how you use a flash meter.

In future posts, more.

Speed lit

Since this blog is called “speedlighter”, and I kind of specialize in lighting, I thought I might do a quick post on quick lighting.

Today, I had a student shoot me, and her dog, using one studio light (a 400 Ws Bowens light). To do this you need to do the following:

  1. Set up a light on a stand;
  2. Add an umbrella;
  3. Shoot near a wall which acts as the reflector (that is why one light is enough!);
  4. Connect the light to the camera using, for example, a cable;
  5. A light meter to measure light and hence to help you set the flash’s power;
  6. Set your camera to f/8, 1/125th second, 100 or 200 ISO;
  7. Now meter to that (i.e. adjust the light until the meter read f/8).

The first test shot should be without flash, and should be black.

Then, connect the flash cable and shoot:

Michael Willems

Michael Willems

And then, after that test shot, the object of tonight’s shoot, which was not me, alas:

Duke Dog

Duke Dog

Cute, eh?

Note the simple composition, blurred background, the excellent composition and tilt (see Friday’s post), and note the catchlight from the umbrella in Duke’s eyes. (If we had shot through an umbrella, the catchlight would be even more simple, round).

Meter the light

You know how in 1970 photographers always used to use light meters?

Like this one, in a pic from the recent photo show:

Michael Willems holding a light meter

Michael Willems holding a light meter

Yes that is right: I am using a light meter. In 2010. And like most working photographers, I use one often.

Why?

Here’s why.

1. Type of meter. The light meter built into your camera is a reflective meter. It meters light that is reflected off the subject.  So if the subject is dark you might get a long exposure time (little light is reflected off it, so your camera sees little light), while if the subject is bright, you might get a short exposure time (a lot of light is reflected, so your camera sees a lot of light).

This means that the subject affects the metering. This is wrong. Think of a bride or a groom in a room. The bride would cause a fast shutter speed (see above), causing the room to be too dark, while conversely the groom would cause the room too bright. Clearly the subject’s brightness is absolute and should not cause the exposure to vary.

An incident light meter, and that is what hand held light meters are, measures the light falling onto the scene. The subject’s brightness has no effect at all. Problem solved!

2. Flash. The only way to meter a flash of light is by using  flash meter. You can use the histogram and a lot of trial and error, but that is just that: trial and error. A light meter gives you the right result.

So in a studio setting, or when using manual flash, you use a light meter. Now you turn it to “flash meter”. And again, guaranteed results.

And that is why we use them still. Like in this shot from this weekend’s show:

Bodypaint Model

Bodypaint Model