How Do You Know if You Have a Correct Exposure?

Setting a correct exposure is foundational to good photography. But what is a correct exposure? 

A correct exposure is one that you are happy with. It means you have set the aperture, shutter speed, and ISO controls well. The result is that not too much light or too little light has made an impression on your camera’s sensor.

But choosing the correct exposure settings can be a bit like deciding what to wear for a night out. Or like determining how much chili to add to a Thai curry. You have to control the balance for it to be most effective.

Setting a correct exposure is a subjective process somewhat governed by technical considerations. You can automatically control the settings on your camera, or you can manage the aperture, shutter speed, and ISO in manual mode. Manual mode gives you more creative freedom to expose your subject. You can make it appear brighter or darker than it actually is. Doing this is one tool a photographer has to capture the mood in their images.

A technically correct exposure is said to be one that contains detail in the shadows and in the highlights of a photo. The photo will also contain a good tonal range. Many photographers tend to strive for a technical proper exposure. This is fine if that’s what you like.

In this article, I am exploring the balance between the technical and creative aspects of a correct exposure. Sometimes these are the same. Other times they are not.

Finding the Balance of a Correct Exposure

Some genres of photography are best with technically correct exposures. Setting the exposure triangle so enough light hits the sensor. So detail remains in the shadows and the highlights. So the scene has a broad range of tonal values.

Other genres are more suited to photographers who like to make creative choices to create a mood and set an atmosphere in their photos. If parts of the composition are very dark or bright, this adds impact to a photo.

There is always room for cross-over too, as the best photography is not confined to a set of rules. Capturing images exposed how you want them to be is one of the key creative components in photography. This should not be dictated by a bunch of technical rules.

But don’t toss out the baby with the bathwater. Making a perfect exposure includes managing the camera’s exposure settings. And doing this with an understanding that results in the right amount of light hitting the sensor.

Too much light results in overexposure. The image is too bright. With too little light underexposure occurs and the image is too dark.

Your camera is a complicated piece of electronic hardware. That’s unless you’re using a old-school film camera. Either tool has limitations. You must manage the aperture and shutter speed and ISO to capture well-exposed images that you can then apply post-processing to.

Seek to find a happy place where the technical and creative aspects of photography collide. When they do, the combination makes the perfect exposure. One that’s a balance between the technical and creative aspects of photography.

Dynamic Range and Tone Range

Dynamic range is the luminance range a camera’s sensor is able to record, between black and white. The term ‘tonal range’ describes the number of tones captured in a photo.

The dynamic range is limited in any camera. In a single frame, the sensor in your camera is not capable of recording the same broad range of tones we can see with our eyes. This is why it’s important to manage your exposure triangle settings well. 

The tonal range in a photo depends on the following:

• How much light is illuminating the scene?
• The quality of the light.
• Exposure settings.
• The tonal range in the subject.

All of these factors must be considered independently but not exclusively. Combined they will help you produce well exposed photos.

How Much Light is Illuminating the Scene?

Whether you are taking photos where there’s a lot of light or not much light, this will have an influence on the camera settings you choose.

When you are using your camera in manual mode, you obviously will have to choose the best settings for a correct exposure. In any auto or semi-auto exposure modes, your camera will decide what settings to use. A faster shutter speed, a narrower aperture and/or lower ISO settings when a scene is well lit. In scenes with low light, a slower shutter speed, wider aperture and/or higher ISO are needed.

What About the Quality of Light?

Hard light or soft light? A scene illuminated by more than one light source, or with reflected light affecting it. These various qualities of light affect the tonal range that might be captured.

In hard light the tonal range is often greater, but there may not be a full range captured. This depends on the subject and the exposure settings. In hard light, you can make an image that’s only black and white, with few or no mid-range tones.

Soft light is more likely to provide opportunities to create exposures with more mid-range tones. The shadows will not be so dark nor the highlights so bright as with hard light.

In scenes lit from more than one source, the tone range in a photo can be varied greatly when you have control over the lighting.

Exposure Settings Affect Tonal Range

Choosing a wider aperture for a shallow depth of field affects your exposure. As does opting for a fast shutter speed to freeze motion. Balancing an aperture of f2.8 requires a fast enough shutter speed. Setting your shutter speed to 1/15th of a second on a sunny day, you’ll need to adjust your aperture to a narrower setting. It will become challenging to achieve a shallow depth of field. Using ISO 100 will help, but may not be enough. Waiting until there is less light will help you get a correct exposure and a shallow depth of field.

To capture a perfect exposure and maintain creative control over aspects such as depth of field and motion blur, you need to understand how to use your camera well. You also need to understand metering well.

Metering Well

Metering for the highlights, mid-tones, or shadows produces varied exposures. Your modern digital camera has at least three exposure meter settings. These read the light in a scene differently. Let’s look at the two main metering modes that will help you get the correct exposure.

One will be averaged metering. Nikon calls this Matrix metering. Canon calls it Evaluative metering. The exposure meter reads the scene from many points and provides an average result. 

Another mode is spot metering. In this mode, you can choose a small part of your photo to make a reading from. Using this mode you can read from a highlight, a shadow, or a mid-tone. With this mode you can be very precise with how you control the exposure of your image.

I often use averaged and spot meter modes to help me decide how to adjust my camera settings.

Learning to set your exposure well manually, or by using exposure compensation, takes time and practice. In my 365 Photography Course, I teach extensively on this topic. There are many practical examples and exercises designed to help you learn to make a correct exposure as often as possible.

How Varied is the Tonal Range in Your Subject?

How much tonal variation in the scenes you photograph must be considered when you want to make a correct exposure. Some subjects will have very little tone range. These are easy to expose for. In any auto mode, you’re unlikely to need exposure compensation because the camera will predict a correct exposure.

Photography of subjects with deep shadows and bright highlights is more likely to challenge a camera’s dynamic range. You may not be able to set a correct exposure that captures detail in the brightest and darkest areas of your picture.

The histogram in your digital camera provides you with information to know when you are losing detail at either end of the tone range. When the histogram graph is bunched up to the left and hits the top, you have lost detail in the darkest parts of your picture. When the histogram is bunched to the right and hits the top, you’ve lost details in the highlights. 

The histogram does not show you when you have a correct exposure, but it is helpful for showing you when detail is not being recorded in an image.

A Correct Exposure is What You Make It

As you can see, there are many aspects to capturing a well-exposed image. Leaving your camera on auto often produces an acceptably exposed image. When the light is diffused, and your subject is not high contrast, you are unlikely to need exposure compensation when on auto.

In manual mode, you can leave your meter set to averaged when the tonal parameters are narrow. In high-contrast scenes using your spot meter will help you decide the settings to use for a correct exposure. 

High contrast means more decision-making. This is because the limits of illumination will be beyond your digital camera’s ability to record every tone.

Learning the technical aspects of exposure control and light helps you to make more informed choices. Once you are confident to manage your camera well you will be freer to become more creative with your photography.