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Digital SLR photography — Understanding exposure compensation

Modern digital cameras do a great job at getting the exposure right — most of the time. Here’s how to get great shots the rest of the time.

Cattle Egret

Exposure compensation allowed me to avoid the white plumage being blown-out (badly overexposed) in this photo of a Cattle Egret.

Why your camera sometimes gets it wrong

Imagine all the scenery surrounding you was made of paint. Scoop up all those colours and stir them up, and the resulting gooey mix would most likely end up a boring mid-toned grey.

That’s sort of how your camera thinks. It samples the amount of light and dark it ‘sees’ in a scene and assumes that when it all gets averaged out the result should be not too dark, not too light. Just a mid-tone. If it averages out lighter than a mid-tone, then the camera decides there must be too much light coming into the lens and so it reduces the exposure. And if things average out dark then it increases the exposure.

Because most scenes contain a mix of light and dark, this averaging-out method works pretty well and that’s why the exposure will be pretty much right, more often than not. But what if you’re photographing a scene that only has light-toned things in it? Like for example, a white rabbit on snow.

underexposed shot of a bird

A bright sky caused this photo to be badly underexposed.

correctly exposed shot of a bird using exposure compensation

Much better. Exposure compensation (+ 1 stop) made everything lighter. But the colours look kind of washed out. Now, what could be causing that?


The camera will ‘see’ nothing but white and when it averages that all out, it ends up with — you guessed it — white! It decides that just can’t be right because it’s been programmed to think everything should average out mid-toned grey. So it reduces the exposure. The result will be a photo that is badly underexposed, with a grey rabbit against grey snow. Now the camera’s happy, but you’re not.

So, what can you do?

The good news is your digital SLR (and some of the smarter compacts) will most likely have a function called exposure compensation.

At this point you’ll need to look at your camera’s manual to find out which knobs and dials activate it. But once you know how to turn on that setting, here’s what you do.

First of all, you’ll see that exposure compensation is measured in stops. Stops is a word that refers to your aperture settings.

If your camera keeps making things too dark, you increase your exposure by setting your camera’s exposure compensation to a positive number of stops.

And if you want to decrease your exposure (make things darker) you set it to a negative value.

Usually, one stop will make a world of difference to your photo and you can test if you need more or less by taking a shot and glancing at your histogram.

As you take more and more photos, you’ll soon start recognising the kinds of situations where your camera is likely to get things wrong, when exposure compensation is needed. The examples below illustrate some of the things to look out for.

Extremely bright background

underexposed shot of a Little Pied Cormorant

Here’s how the camera exposed the photo of this Little Pied Cormorant at its default (automatic) setting. It is clearly very underexposed.

properly exposed shot of the same bird

… and here’s how the same scene photographed with +2 stops of exposure compensation. While I was adjusting the camera the bird was also kind enough to turn its head slightly, which improved the shot a little more.

When I saw the Little Pied Cormorant shown at right it was an auto-exposure nightmare. Not only was the bird back-lit, meaning that the parts of the bird visible to me were in shadow, but sunlight was reflecting right off that water around it, throwing up a huge amount of glare. That bright glare was going to play havoc with the camera’s automatic exposure settings. Leaving the camera with its default settings would have given me the underexposed photo shown at right.

Now, I could perhaps have used a flash to light up the front of the bird, but the bird was a long way away and my flash was an even longer way away (at home). I knew the little pop-up flash on the camera wouldn’t be enough.

I knew the camera would make things underexposed, resulting in the bird being a silhouette, so I set exposure compensation to +2 stops. The result was the next version shown here, where the water is now pushed almost to white, and the bird is correctly exposed.

Bringing out the detail in a white texture

When an area of white texture is hit by bright sunlight, the camera will often ‘blow out’ the detail, which is to say it over-exposes the shot so badly that big chunks of the image go completely white, with no image detail captured at all. Once an area of white is overexposed that much then no amount of pulling levers in your image-editing software is going to get that detail back. So at times like that, it can be a good idea to deliberately underexpose your shot a little.

properly exposed shot of an egret

In this picture of an egret, I didn’t want to lose that white feather texture so I set my camera’s exposure compensation to minus one stop. Thanks to that setting, those feathers turned out fine.

How do you know if you should make things darker or lighter?

The easiest way is to take a test shot and see how it looks. Checking your histogram if often a good idea too.

However, a very general bunch of guidelines are:

Too confusing? Then just fire off that test shot and work your way from there. You’ll quickly get a feel for this kind of thing.

Photography

Beginners’ series on digital SLR photography

The essential basics

Digital SLR photography — a beginners’ guide
A quick guide to understanding your new toy

Learning from examples
Picking up where the first article left off

Understanding aperture
This is one of the fundamental tools for controlling exposure.

Understanding shutter speed
This is another of the fundamental tools for controlling exposure.

 

Making sense of technical stuff

Megapixels
How many is enough?

How much camera gear do you need?
Sometimes, less really is more

How to choose a lens
Making the right choices can improve your shots and save you money

newTips for using tripods
Getting the most out of them

JPG versus RAW
Which is the best way to work?

Understanding histograms
Making sense of this handy tool

APS-C vs full frame
The differences explained, and what it means to your photography

Pixel density in sensors
Helping APS-C cameras photograph distant objects.

Fast lens, slow lens
What’s the difference?

Understanding colour temperature
It doesn’t have to be complicated.

Understanding resolution
What it means, as it applies to digital photography

 

Photography words explained

What’s a 100% crop?
I explain a term you often hear in digital photography

newWhat are specular highlights?
You’ll recognise them when you see them

newWhat is bracketing?
A commonly-used word for a handy trick

 

Photography at night

Photographing small critters
in the dark

How I take my shots when there’s no light

newTaking pictures of the moon
You need a fairly long lens, and these simple tricks

Common problems and their solutions

Washed-out colours in photos
Why it happens, and how to prevent it

Understanding exposure compensation
Why your photo subject can look so badly exposed, and what to do about it

Understanding dynamic range
Dealing with too much contrast

Working in harsh light
Getting some of the colour back into midday photography

Getting sharper pictures
Understanding the things that stop your photos from being tack-sharp

Noise in your images
What causes it, and what can you do about it?

 

Taking things further

Using a telephoto lens to blur the background
Here’s an easy-to-understand explanation of why it happens

Macro photography part 1
Using your DSLR for bug shots

Macro photography part 2
Ironing the bugs out of bug shots

One simple trick
The easiest way to get better wildlife photos

Wildlife photography
Tricks the pros use to get better pictures of critters

Bird photography part 1
Small, distant, and feathered does not have to mean a bad photo

Bird photography part 2
More hints for beginner bird photographers

How I take photos of frogs
These tiny critters require a technique all their own.

Using software to ‘fix’ your photos
A few suggestions for image editing

 

Advanced stuff

Image Stacking
Using software to achieve extraordinary depth of field

Sneaky deep-etching
A fast way to cut complicated objects out of their backgrounds

 

Other photography stuff

BLOG (sort of)

The elusive waterskiing duck
It started out as a fun idea …

PHOTO GALLERY

Pics of Australian critters
Some of my recent images

PHOTO SALES

Looking for the right picture?
A small selection of the photos available


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