Why I Use Exposure Compensation

Most of the time modern digital cameras will do a pretty good job adjusting the shutter speed, aperture, and/or ISO to get a well-exposed photograph.  Other times the photo comes out too dark or too bright and can't be saved.  Why does this happen and what can be done to get a better exposure?

Digital camera light meters work by evaluating light reflected off objects in the frame.  Depending on if you are in aperture priority, shutter priority, or manual, the camera will attempt to adjust one or more settings to make the overall exposure close to a standard middle gray (also known as 18% gray).

If most of the things in the frame are very dark, the camera will attempt to brighten up the exposure. If the subjects are mostly bright it will darken the exposure so the overall scene is close to 18% gray.  As smart as modern cameras are, they can't tell what parts of the scene are important.  While the overall scene may be properly exposed, the important subject may be too dark or too bright.

Default exposure - 1/1000 sec., f/6.4, ISO 160

In the photo above, the bright sky behind the Bluebird caused the Bluebird to come out dark.   There are a few things that can be done to fix this problem.  I could (1) set my camera to spot metering so I only measured the brightness of the bird, (2) move so the background is not so bright, or (3) use Exposure Compensation to adjust the exposure.

In most cases, I don't change the metering mode when photographing wildlife. Switching metering modes on most cameras is cumbersome.  The bird would be gone by the time I made the changes.  

Exposure Compensation allows me to override the exposure settings that were determined by the camera, in order to darken or brighten images before they are captured. On my Fuji X-T1, X-T2, and X-T3 cameras there is a dial on the top of the camera that I can turn to quickly and easily adjust the exposure compensation. Unfortunately, exposure compensation is not as easy to change on all cameras.  You will need to learn how to change it on your camera.

Using the Bluebird as an example, I adjusted the exposure compensation to make the photo 1 2/3 stops (EV) brighter and took the photo again.

+1 2/3 EV exposure - 1/1000 sec., f/6.4, ISO 320

When photographing birds I have my shutter speed and aperture fixed and let the camera adjust the ISO.  When I told the camera to make the photo 1 2/3 stops brighter it did so by doubling the ISO. You can see the second photo is noticeably brighter than the first.

How the camera makes the adjustments depends on what mode you are using

• Aperture Priority - the camera will leave the aperture where you set it and adjust the shutter speed.
• Shutter Priority - the camera will leave the shutter speed where you set it and adjust the aperture.
• Manual with Auto ISO - the camera will only adjust the ISO.  This is the mode I was using.
• Exposure compensation may not be available if you are using Auto mode.

Being mirrorless cameras, my Fuji's show me the adjusted exposure and live histogram in the viewfinder as I am composing the shot.  With DSLR cameras you may have to make a shot, check out the exposure, adjust and shoot again. An alternative is to use exposure bracketing to automatically take 3 or more shots at different exposure compensation settings.

There is another alternative that can help get the right exposure.  The problem in this example is that sky is too bright compared to the bird.  Sometimes we can maneuver ourselves to change the background to something closer to the brightness of the subject.

1/1000 sec., f/6.4, ISO 1250

In this third shot, I moved so that there were trees behind the bird instead of the sky.  I didn't have to make any adjustments to the exposure.  Most of the time it's not practical to move but it does a great job when I can.

I hope these three examples and explanation gives you a feel for how Exposure Compensation works.  I suggest you figure out how to use it on your camera and give it a try.

Using Exposure Compensation

“Each day brings new opportunities, allowing you to constantly live with love—be there for others—bring a little light into someone's day. Be grateful and live each day to the fullest.”
― Roy T. Bennett, The Light in the Heart

Light is the most important part of photography.  Without it, there would be no image, no memories, no joy in a photograph.  But, too much or too little light can be detrimental to our photos.  Understanding light is key to making better photos. 

Our cameras don't understand light.  They have powerful computer processors that measure all the light coming in through the lens and hitting the sensor, but they don't know anything about the subject, what is important in the photo, or what is unimportant.  The software developers who program those processors write algorithms to take all the inputs and make a decision on the three factors that make up the exposure triangle - shutter speed, aperture, and ISO.  Depending on your camera settings one, two or all three of these are constantly being adjusted depending on the light the camera sees at that instant.  Without knowing your composition your camera can sometimes make bad decisions.

Take this photo as an example.  The conditions were harsh.  It was a bright sunny day with harsh direct light.  The breeze was blowing and the Columbine flowers were in constant motion.

1/4000 sec, f/2.8, ISO 1600

I was shooting with an aperture of f/2.8 to create a shallow depth of field making the center flower stand out from the background.  The high ISO was to get a very fast shutter speed to freeze the motion of the flowers.  The camera saw all the light and decided on a shutter speed of 1/4000 of a second.  Even with that fast shutter speed, there was too much light.  Although the overall exposure was not bad, the main subject was overexposed and the photo was ruined.

There are a number of ways to fix this, and none involve post-processing (editing) on a computer later.  If you are comfortable shooting in full manual mode, you set the aperture, shutter speed, and ISO while keeping an eye on the histogram.  My personal preference is to stay in aperture priority mode, where I spend most of my time, set the ISO, and let that advanced processor in the camera figure the shutter speed at that instant.  Remember I said the flowers were constantly blowing around.  That made the light constantly changing.  Instead of setting the shutter speed myself I gave the camera a hint that the exposure needed to be turned down. 

Almost every camera (even some cell phones) has a setting called exposure compensation.  It is often a button on the top or back of the camera that has a +/- symbol.  Some cameras have this setting buried down in a menu.  This typically only works when the camera is in Program, Aperture Priority, or Shutter Priority mode.  By using exposure compensation I was able to tell the camera to alter the calculated exposure by a given number of stops.  In this case, I dialed in a -2 EV exposure compensation and shot again.  I also lowered the ISO to 400 because I didn't need it that high to get the shutter speed I was wanting.

1/6000, f/2.8, ISO 400

Now, the subject of my photo is properly exposed.  The background is now almost black.  That works great because the background is unimportant and making it dark it makes the red flower jump out.

A common exposure problem occurs when the background is brighter than the subject.  By default, the camera will expose so the subject is dark and the background is correct, like in this photo.

By dialing in a +1 2/3 EV exposure compensation I am able to brighten the bird so that details in the feathers and eyes can be seen.  By making this adjustment the sky becomes overexposed.  This is fine because the subject is the bird, not the sky.

The key to knowing when to adjust the exposure compensation is knowing what the subject is and if it is properly exposed.  If the subject is too bright or too dark, throw in some exposure compensation to properly expose the most important part of the photo.

You may be tempted to assume you can correct the exposure later in post-processing.  Don't be fooled.  Parts of your photo that are overexposed often cannot be brought back and brightening underexposed photos can introduce digital noise.  It's much better to get the exposure right when you make the photo than to try to correct it later.

If you find this tip useful please subscribe to my blog to get future tips emailed to you.  If you have questions, feel free to contact me and I'll do my best to answer them.