Overexposure Strategies

Great Egret at the Horicon Marsh

Great Egret
f/7.1, 1/250, ISO 400

This ruggedly handsome Great Egret is adorned with his white breeding plumes cascading over his tail.  The plumes are present only in spring and early summer.  Both male and female egrets have them.  Once valued for use on hats, egrets were almost hunted to extinction.[1]  Great Egrets are aptly named since they are the largest egret.

It was a highlight to see this beautiful bird roosting in a tree today, but, as you can see, I blew the highlights.  Some of the white feathers are overexposed.  Once that happens, there is no getting the detail back in post processing.  What can I do to improve this photo?  Here are 6 strategies to deal with overexposure on white birds.

  1. I took this picture at 5:05 p.m. central time.  I could come later in the day, or earlier in the day, when the light is more golden and there is less contrast.  If the only time I have to shoot is in the middle of the day though, I’m still going to go out and take advantage of that.
  2. I could change my angle to the bird.  With the light behind me and on the front of the bird, it makes the bird look more flat and creates fewer shadows. Shadows add depth.  If I could change my position so the bird is lit from the side there would be more detail. I was stopped on the shoulder of Highway 49 and changing my position wasn’t an option.
  3. I was shooting JPEG images and using aperture-priority mode with my Canon 7D.  These are my typical choices.  I chose a 7.1 f-stop.  The lowest aperture my 150- 600 mm lens allows at 600 mm is f/6.3.  I wanted to keep the f-stop low to blur the background and make the bird stand out.  The lower the number the more wide open the aperture and the more light that is let in to the camera.  This decreases the depth of field so the bird is sharp but the background blurs. The camera set the shutter speed at 1/250.  I set the ISO to 400.  This setting let in too much light.  I have several choices if I want to stay in the aperture-priority mode.  If I increase the f-stop to f/16 to increase the depth of field, the camera will automatically change the shutter speed to compensate.  A change in one control causes an equal change in the number of stops in the other control. I would get the same amount of light.  The aperture is like the diameter of a garden hose.  The shutter speed is how long I turn the water on.  If I have a hose with a large diameter, I only have to turn the hose on a short time to water the garden.  If I decrease the diameter of the hose I am using, I have to turn the water on longer to get the same amount of water on the garden.  Either way, it’s the same amount of water (or light, in this case).  If changing the f-stop in this mode doesn’t help, what else can I do to change the exposure?  I can change the ISO.  ISO is the camera’s sensitivity to light.  Sadly, changing the ISO in aperture-priority mode also causes the camera to change the shutter speed to compensate.  My garden is getting the same amount of water.
  4. The option to use, if I want to stay in aperture-priority mode, is the exposure compensation feature.  The scale for this feature is found in the lower bar in the viewfinder.  I have a dial control on the back of my camera that I can rotate until the arrow on the scale lines up at “0” indicating the exposure is correct.  In this case, I may have to adjust to -1 or -2 because the majority of the photo is darker trees and cattails (prior to my cropping it).  If the photo was mostly the white egret, then I may have to go to +1 or +2.  Exposure compensation only works with automatic exposure modes.
  5. I could leave the comfort zone of aperture-priority mode and enter the scary territory of manual mode.  Now I can set the large aperture I want, set the ISO, and change the shutter speed to a faster speed until the exposure scale is at 0.  That doesn’t seem too scary.  But how do I know the exposure is giving me the detail I want in my photo?  I can check the dreaded histogram.  Actually, that isn’t so frightening either.  I press the “playback” button, then the “info” button three times and the RGB histogram is displayed.  When shooting JPEG images, I want the color that is farthest to the right to be a half stop from the right margin of the graph.  In RAW, the color farthest to the right should touch the right margin of the graph without climbing up the margin. So I can take a shot, check the histogram, and adjust my shutter speed or ISO as needed.
  6. There is one last strategy.  I should turn on my highlight alert feature.  This is found in the menu.  Push the “menu” button.  Search for “highlight alert” and enable it.  Now when I view my images in the playback mode there will be blinking black areas where I overexposed the bird.

I am excited to try these strategies and stop overexposing the abundant white feathered birds at the Horicon Marsh.  I will let you know how the strategies work in a future post.

If you would like to read an excellent article about the manual exposure mode written by John and Barbara Gerlach you can find it here. You might also like their book Digital Wildlife Photography.  Their chapter on exposure strategies will give you more details and examples.

What strategies do you use to keep from overexposing your shots?  Join the discussion in the comments section.

[1] John Eastman, Birds of Lake, Pond and Marsh:  Water and Wetland Birds of Eastern North America (Mechanicsburg, PA:  Stackpole Books, 1999), 200.

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