Photography exposure control for each shooting mode (exposure part 4)

For the purpose of this tutorial on exposure control in all shooting modes, let’s assume that you’re not using auto ISO. So, once you set your ISO, it stays at that setting and won’t change with the changing conditions.

What shooting modes are there?

• Program mode
• Aperture priority mode
• Shutter priority mode
• Manual mode

Auto mode and scene modes are fully automatic camera settings for exposure, which means you can’t control exposure in these shooting modes. So I haven’t included them here. 

To understand when and how to use each shooting mode, we must first understand:

1. The advantages of each shooting mode
2. Exposure metering for program mode, aperture priority and shutter priority modes

Now let’s look at the exposure control decisions you need to make so that you can decide on the best shooting mode to use. 

1. The advantages of each shooting mode

To fully appreciate the advantages of each shooting mode and exposure control in all shooting modes, we need to compare the four shooting modes.

Aperture priority is the next most popular shooting mode after program mode for beginners, so we’ll use this as the basis of comparison.

Aperture priority (A or AV) vs Program mode

Although with both shooting modes the camera makes the final decision on controlling the exposure, in aperture priority mode you have greater creative input.

Program mode

In program mode the camera decides on both the aperture and the shutter speed. It chooses the best handheld option for the lighting conditions to ensure that shutter speed isn’t too slow.

Aperture priority mode

In aperture priority you control your aperture setting and the camera automatically sets the appropriate shutter speed for the lighting conditions.

This gives you creative control over the depth of field (background blur) of your image for a correctly exposed image. Most of the time – I’ll explain why in a moment.

However, your camera doesn’t know if:

• Your subject is moving or still
• You’re handholding your camera or if it’s mounted on a tripod

So it might set a shutter speed that’s too slow.

Why use aperture priority mode?

Aperture affects depth of field in an image. So you set either wide aperture for a blurry background, or narrow aperture for front to back sharpness.

It’s up to you to decide on whether you want:

• A blurry background (large aperture/small f number)
• Or front to back sharpness (small aperture/large f number)

Your camera will adjust the shutter speed setting accordingly.

Which leads me to the next comparison…

Aperture priority vs Shutter priority (S or TV)

In aperture priority mode, you need to keep an eye on the shutter speed to make sure that it doesn’t drop too low.

So when deciding on aperture priority vs shutter priority remember that the camera doesn’t take into account whether you’re handholding the camera or have it fixed to a tripod.

Shutter priority mode

In shutter priority you control the camera’s shutter speed.

However, your camera doesn’t take into account the maximum f-stop of your lens. So, if you’re not aware of what’s happening with the change in aperture, you could get an incorrect exposure.

What’s more, your camera is limited by your choice of lens.

It can only go to the maximum (or minimum) f-stop of your lens. So if you select a shutter speed that needs an aperture setting beyond this for correct exposure, it’ll overexpose or underexpose your photo.

Why use shutter priority mode?

Use shutter priority when photographing moving subjects to:

• Freeze the action with a fast shutter speed
• Show movement with a slow shutter speed
• Use a slow shutter speed for a long exposure to capture a very dark scene.

Aperture priority vs Manual mode (M)

Aperture priority is easier to use than manual mode when you need to grab the shot quickly and there’s a lot going on.

In a fast moving situation, like the confetti toss at a wedding (see photo at the start of this tutorial), you don’t have the time to keep an eye on the exposure indicator, as well as adjust the aperture or shutter speed accordingly. This is when aperture priority mode is helpful.

Especially if you’re not 100% comfortable working in manual mode.

Manual mode

Manual mode beats all shooting modes for putting you in creative control of your camera and the end result of the shot.

Using manual mode allows you to change shutter speed and aperture settings from one shot to the next to capture a variety of images in the shortest amount of time. 

It does of course take practice to get really comfortable for fast moving situations, but it’s worth it. Besides, not every photoshoot moves quickly.

Why use manual mode?

Creativity and complete control over your camera and the outcome of your image.

2. Exposure metering for shooting modes

In these semi-automated shooting modes you leave the final decision on exposure to your camera:

• Program mode
• Aperture priority mode
• Shutter priority mode

Unless you know how to control exposure in all shooting modes.

In manual mode you make the final decision on exposure. However, you still need to be aware of how your camera’s exposure meter can be confused so that you can accurately adjust the exposure.

What confuses the exposure meter?

Let’s take the example of a black cat on a white couch vs white cat on a black couch.

Both scenes are black and white, but one has a large bright area (white couch) and the other has a large dark area (black couch). If you had exactly the same light in each scenario, your camera would meter it differently.

The white couch reflects more light than the black couch and your camera’s inbuilt exposure meter measures reflected light.

As your camera wants to make everything an average gray, it’ll under expose the white couch scene and over expose the black couch scene.

Here’s another factor to consider – composition

What if you get in close and fill the frame with the cat’s face? No couch included.

A white cat photographed on a white couch will be the same exposure reading as a white cat photographed on a black couch (ignoring for the sake of simplicity, the negative fill caused by the black couch).

Let’s compare exposure control for these two photos

Our two models have similar coloring and are both wearing dark clothes. In each scenario the models are in the shade and lit with natural light. The only difference is the background – one is light and the other is dark.

I used manual mode with spot metering and metered the exposure off the models’ faces. The aperture for both shots is f2.8.

• If matrix metering had been used, the bright background would have influenced the exposure reading.
• Center weighted metering would have caused an inaccurate exposure, because of the dominance of her dark coat and hair.
• A wide aperture was used to blur the background and so separate the subject from the background.
• If I’d used aperture priority mode, to create a blurred background, I would have increased the exposure compensation to counteract the camera’s exposure meter wanting to under expose the image

• With matrix metering the dark wall and her clothes would have dominated the exposure metering and the model would have been over exposed.
• However, I could have used negative exposure compensation to counteract the camera’s desire to over expose the image.
• Partial or center weighted metering would have metered the centre of the image, mainly the background, and not the model.
• If I’d used aperture priority, I could also have decreased exposure compensation.

Exposure metering modes

As I said, you’ll need to decide how much of the scene you’re going to photograph, so you know much of the scene to meter. In other words, which metering mode to use? We discussed exposure metering modes in part 2 of this series, so I’ll just mention them briefly:

Matrix metering measures the exposure of the entire scene.

Partial metering (Canon only) meters 8 – 13% of the center of the scene.

Center weighted metering measures about 60% of the center of the scene, regardless of where you’re focusing.

Spot metering meters the area around your single focus point, which you’ve selected. This is about 2 – 4% of the scene.

3. Exposure compensation

Now that you’ve decided on the best metering mode for the situation, you can decide if you need to use exposure compensation to overcome your camera’s limitations using any shooting mode. 

Just remember that you won’t see the exposure indicator until setting your exposure compensation and moving it from 0, either positively for a brighter exposure or negatively for a darker exposure.

Knowing how to control exposure in all shooting modes puts you in creative control of the final exposure.

Just because you’re not shooting in manual mode, doesn’t mean you can’t get creative with your exposures.

Next up – part 5 – pros, cons and how to use auto ISO

Sometimes there’s so much going on that you need a little help. Next, we look at the benefits and limitations of using auto ISO – even in manual mode!

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If you have any questions about using the different shooting modes for controlling exposure, let us know in the comments.

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