Originally published in The Blue Bill, the journal of the Kingston Field Naturalists, Volume 66, No. 4, December 2019

Freezing the Action – Shutter Speed and Shutter Priority Mode

One of the major challenges of wildlife photography (and sports photography for that matter) is the need to choose a sufficiently fast shutter speed. Like all photographers we need to balance available light, depth of field, metering modes and focus points. But unlike, say, landscape or portrait photographers our subject matter tends to move quickly in unpredictable ways.

If our camera’s shutter speed is fast enough we will be able to “freeze” the action of fast-moving subjects and get a crisp image. So in principle the solution is to always use a fast shutter speed. And there are some circumstances where this approach will work. But much more often we will be engaged in a balancing act, adjusting variables such as shutter speed, aperture, and film speed (ISO) to get a correct exposure.

The Basics of Exposure

In very simple terms the image your camera produces is governed by the amount of light that falls on the sensor. A correctly exposed wildlife image will show the creature or plant in natural light with no areas that are too dark (underexposed) or too bright (overexposed), and will be crisp with no motion-induced blurring. Photo 1 shows an American Pipit, and to my eye the exposure is good – all detail is visible and the bird’s foot is frozen in mid-stride.

Exposure is controlled by three settings: aperture (the amount of light that the lens allows to reach the sensor); shutter speed (the length of time that the sensor is exposed to the light); and film speed or ISO (the sensitivity of the sensor).[1]

Each of these variables has implications that the photographer needs to understand:

Shutter speed

As noted above, the primary way to get a crisp exposure of a moving animal (or a plant blowing in the wind) is to use a fast shutter speed. The downside of fast shutter speeds is that less light reaches your camera’s sensor. Shutter speed is expressed in fractions of a second. Each step up in shutter speed (e.g. from 1/250 to 1/500) halves the amount of light available. So except in very bright, sunny conditions faster shutter speeds can lead to underexposed images. To an extent you may be able to fix underexposure in post-processing, but artificially adjusting the exposure by more than a small amount adversely affects the quality of the image.

For stationary subjects you can use a slower than normal shutter speed and hope for the best, but typically the creature will move just as you snap the shutter. Photo 2 is a Coatimundi seen just after dawn. I had to use a slow shutter speed and a high film speed to get the shot. If you look closely you will see that the face is slightly blurry as it moves its head to the side.

So if shutter speed isn’t the whole solution, what else can you do to increase your chances of getting a crisp image?

Aperture

Wide apertures allow more light in, so in the low-light conditions we are often dealing with a wide aperture seems like a good choice. The more light that passes through the lens, the faster your shutter speed can be. But as you might guess there are no easy solutions here. First, telephoto lenses capable of wide apertures are ruinously expensive. For example the Nikon NIKKOR 300MM ƒ2.8G ED lens, a favourite of professional wildlife photographers, will set you back a cool $6899.99 plus HST. So most of us will be using lenses with narrower apertures, and thus will have less light to play with.

Moreover, the wider the aperture, the shallower the depth of field. For the wildlife photographer, this creates a problem: the image may be correctly exposed but parts of the creature are not in focus. Photo 3, a Pearl Crescent, is correctly exposed. But even at ƒ7.1, a middle of the range aperture, the depth of field is shallow enough that the wing closest to the viewer is not in focus. The tails of birds can also fall prey to depth of field issues. In photo 4 the tail of the Canada Jay is a bit soft-edged, as it was beyond the optimal depth of field.

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Film Speed (ISO)

Before the advent of digital cameras, photographers adjusted for low-light or fast-moving subjects by using faster film. So instead of ISO 64 or 100 film they might switch in a roll of ISO 200. This involved a big trade-off in image quality, as faster films producing grainer images. ISO 400 was about the maximum usable speed.

Now we have digital cameras capable of ISO equivalents of up to 51,000 so is the problem solved? Yes and no. Good quality digital cameras can produce very good images at higher ISO ratings, but only to a point. Just as fast film was prone to graininess, digital camera sensors can generate “noise” at higher speeds.

If you are interested in learning more about digital noise I recommend this post on the Photography Life site: https://photographylife.com/what-is-noise-in-photography

With my camera I can get excellent images at ISO 800, and very good ones up to ISO 1000. Speeds faster than that can work reasonably well depending on what you want the image for. Photo 2, for example, was shot at ISO 2000. The image is reasonably crisp and good enough for a record shot, but if you look above and to the right of the creature’s haunches you will see that the image becomes fuzzy (“noisy”) with some random colour blobs.

So what does it all mean? Simply that there is no single recipe for achieving crisp, properly exposed images of wildlife. While we are in the field we have to make continuous judgments about shutter speed, aperture and film speed to enable us to get the images we want.

Shutter Priority Mode

If you spend too much time thinking about these variables you may end up missing some of the action you went out to photograph. So most wildlife photographers use their camera’s mode system to automate part of this work.

All DSLRs and most bridge cameras have four basic operating modes: Manual, Shutter Priority, Aperture Priority and Program. I want to explain Shutter Priority mode here because I think it is the most useful option for wildlife photographers.

Your camera will have an easily accessible way of selecting this mode – most often by a rotating dial on the upper right side (Photo 5). For most DSLRs rotating the dial to S puts you in shutter priority mode. Eccentrically, Canon and Pentax call it “Tv” for time value, but the effect is the same.

When you are operating in this mode, you can select the film speed and shutter speed you desire and the camera will automatically adjust the aperture within its limits to ensure a correct exposure. If there is not enough light to get a correct exposure at maximum aperture the camera will warn you somehow, often by inactivating the shutter release. Check your manual to see how your own camera works and what adjustments you can make.

You can actually go a step further and automate your choice of film speed as well. Somewhere in the menu system of your camera there will be an option to select “auto ISO”. This is a tempting option for wildlife photography, as it minimizes the chance of a missed shot. However beware of the fact that cameras left to their own devices tend to bump up the film speed to fairly high levels, so if you use this function check your manual to see if you can set an upper limit on auto ISO.

Recommended Shutter Speeds

So the final piece of the shutter speed puzzle is: how fast is fast enough?

In principle, unless forced to by low light I would recommend a minimum shutter speed of 1/500 for wildlife. Birds and mammals, even if they appear stationary, are often flicking their ears or looking around, so it’s best to err on the safe side. I did a quick check of the wildlife photos I am most proud of and almost all were shot at 1/500 or 1/640. There are exceptions, such as the Chestnut-naped Antpitta at photo 6 (1/00 at ƒ5.6) but I was fortunate that the bird held still for a moment.

For frogs, turtles, and perched butterflies and odonates you can often get by with a slower speed, as they can sit still for lengthy periods. But the Snapping Turtle at photo 7 was being aggressive so I needed 1/500 to freeze her.

Special Cases

Birds in Flight

There is a simple rule of thumb here: the fastest shutter speed you can manage is the one to choose. But you can cheat to some extent based on the type of bird and its activity. The Trumpeter Swan has fairly slow wingbeats, so in photo 8 even 1/250 was enough to get a crisp image. The gliding Red-tailed Hawk in photo 9 was shot in bright daylight so I was able to go to 1/3200 and ensure that the image was crisp.

The Greater Prairie Chickens at a lek in photo 10 were tricky. We were shooting at dawn so there was very little light available, and the birds were actively jousting. I found through trial and error that a shutter speed of 1/2000 was enough to freeze the action. To make that work I had to bump the ISO up to 8000. The resulting image is reasonably good.

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By the way, don’t even think about trying to photograph butterflies in flight. That way lies madness.

Hummingbirds

Hummingbird wingbeats are so fast that it is difficult to get a crisp image even in optimal light. Shutter speeds of at least 1/3200 will be needed. And because their wings move in strange ways to allow them to hover, even if you do get a crisp image it will often look rather odd. So unless you can find a perched bird, I find the best approach is to intentionally allow a bit of blur in the wings, which gives the impression of movement. The Western Emerald in photo 11 was shot at 1/320 while hovering. This is about right for the wings, but as you can see the tail is a bit blurred, so a slightly faster speed would have resulted in a better image.

So that’s the bluffers’ guide to shutter speed. if you have mastered the basic operation of your camera and want to dip your toe into more advanced options why not try experimenting with shutter priority?

Previous posts in this series

• Exposure Compensation: Don’t Blow Up Your Gulls – Wildlife Photography Tips #1

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[1] Almost all cameras now are digital and do not use film, but the term film speed is still widely used to describe this function.