Beecher's Handouts >
Setting Exposure >
13.9 - Autoexposure Lock
You can point your camera at part of a scene—measure the
light—and can lock in that exposure.
Let's say you're photographing the Matterhorn from the
village of Zermatt.
The mountain is in the sun.
The village is in the shade.
Your camera may set the exposure for the shady part of the
scene, Zermatt, and not the Matterhorn.
If so, the Matterhorn would be too bright.
Use the autoexposure lock button to make sure the
camera sets the exposure for the mountain, and not the village.
Do the following.
How to Lock in the Exposure
Nikon DSLRs
Look for the AEL button.
It's near where your right-hand thumb can reach it.
When you press and hold the AEL button, the exposure
is locked in.
1) Press the shutter release slightly to turn the light meter
on.
2) Fill the frame with the part of the scene that you want to
use to set the exposure.
3) In the example, point the camera at the Matterhorn.
4) Press the AEL button and hold.
5) Recompose the scene in the frame.
6) Press the shutter release.
Canon DSLRs
Look for the button with an asterisk icon.
It's near where your right-hand thumb can reach it.
When you press and release the asterisk button, the exposure
is locked in until the light meter shuts off.
1) Press the shutter release slightly to turn the light meter
on.
2) Fill the frame with the part of the scene that you want to
use to set the exposure.
3) In the example, point the camera at the Matterhorn.
4) Press the asterisk button.
5) Recompose the scene in the frame.
6) Press the shutter release.
Make sure the light meter doesn't turn off before you've
pressed the shutter release.
If it does, start over.
A few Canon cameras have an autoexposure lock "button" that
is a lever on the back of the camera at the bottom.
Check your instruction manual.
AFL, Too?
The autoexposure lock button often does double duty as an autofocus lock button.
In your camera menu, you can set the button to:
• Lock in both the exposure and the focus.
• Lock in only the exposure.
• Lock in only the focus.
You may want to set the button to lock in only the exposure.
Examples
Example #1
Let's say you're at the Grand Canyon.
When your light meter "sees" the bright sky, it may set the
exposure for the sky.
The canyon may become too dark.
Point your camera down at the canyon, and lock in the
exposure.
Point your camera at the sky and canyon, and press the
shutter release.
Example #2
Let's say you're photographing some friends standing on the
edge of the canyon, with a bright sky behind them.
If you don't use the autoexposure lock button, the camera may
set the exposure for the bright sky.
Your friend will be in silhouette against the sky.
Instead, walk up to your friends, fill the frame with their
faces.
Lock in the exposure.
The exposure is now set for your friend, not the sky.
While keeping the autoexposure lock button depressed, walk
back and focus, and press the shutter release.
Autofocus Lock, Too?
The autoexposure lock button often does double duty as an
autofocus lock (AFL) button.
In your camera menu, you can set the button to:
• Lock in both the exposure and the focus.
• Lock in only the exposure.
• Lock in only the focus.
You may want to set the button to lock in only the exposure.
