Handheld vs. in-camera metering

Say you're photographing your beer. You put it on a white background; setup your hot light (or some other kind of natural light) the way you want it; you got the right angle; set your camera to Program Mode; focus is good.  You are set to go. <CLICK!>

"Hmmmmm.  Looks kinda dark and grayish", you think to yourself. "What the heck?"

Today's lesson is about using a handheld incident meter vs. using the reflective meter inside your camera.

The Reflective Meter

These days, the meter inside your camera is getting more and more complex.  There are fancy Matrix modes, and even weighted modes and smaller and smaller spot modes.  These allow the average photographer to save money in foregoing the purchasing of a handheld light meter in favor of some other fun gadget like a lens cap holder. (Aren't those fun?)

The trouble is, no matter how complex and hi-techy your in-camera metering matrix is, it still can be fooled.

The way your camera's internal metering works is by measuring the light as it bounces back to you from your subject.  The camera looks at the scene as if it is a perfectly uniform 18% gray, not a can of beer on a white background.  It therefore judges the whole scene to be 18% gray and will give you a reading accordingly.  That means if your subject is white, it wants to darken it; if your subject is black, it wants to lighten it!  Anything to get the scene back to a nice comfortable 18% gray.

Many different scenarios can fool the internal meter.  A dark bar scene, for example, will tell your camera to lighten it up; a blushing bride in a pure white dress in bright sunlight will suddenly find herself in a dingy gray dress.  Unless your scene is perfectly balanced with light and dark, your camera will manipulate your exposure reading to measure 18% gray.

The Incident Meter

On the other hand, the handheld incident meter measures the light as it hits your subject.  This gives you the most accurate reading possible as the incident meter can't be fooled by light or dark scenes.  The camera doesn't have to worry about 18% gray (or anything) as you input the correct exposure settings.  No more "A" for Amateur setting on your camera, Grasshopper, you can now use the "M" for Master setting ;)

Below are two examples of reflective and incident readings:

The left image was shot after measuring through the camera (I inserted the reading on the meter for illustrative purposes).  The right image shows the difference when the handheld incident meter [shown] is used.  A full stop difference!

What happened is the camera was fooled in the image on the left, thinking that the whole scene was 18% gray and inputed the numbers to make it so.  The incident meter on the right gave me the correct numbers by measuring the actual light hitting the scene.

When to Use WHAT When?

Whenever possible, use an incident meter.  But there are times when you can't climb or scratch your way to the light source to measure it, like in landscapes.  Measuring the light on the tips of the far off mountains is totally impracticable unless you're a Mountain Goat.  Your in camera meter is the best option.  Take multiple exposures at different readings to ensure you're nailing the correct exposure.


"This is all great, but I can't afford to drop a couple of hundred bucks on a meter," you say?

Totally understandable.  So long as you understand the concept behind what your camera is seeing, you're half way there.

Also, no one's saying you HAVE to sell your first born to get a basic light meter.  But, I do recommend at least selling your middle child if you need or want to have accurate control of your exposure readings.

A cheaper option is to purchase an 18% gray card for a buck.  Since the card is already 18% gray, there's nothing to trick your camera and you will be well on your way in getting more accurate exposure readings.  Here's how to do it:

  1. First step is to place your card in the scene. Make sure the main light is hitting it, be it the sun or window light.
  2. Step up to the card and focus on it.  Make sure it fills the frame.
  3. Press the Exposure Hold button.  For Canon users it's the *. For Nikon, sorry dudes, but you gotta look in the manual for that one.
  4. Step back, refocus and take your picture.

As simple as that!


Now back to my beer.

I placed my incident meter into my scene and pointed the dome back towards the lens; took note of the reading; and switched out of Program mode into Manual mode and finished by inputing the new numbers.


MUCH better!