Category Archives: Wildlife Photography

Birds, Photography, Wildlife Photography

Autofocus Modes – Wildlife Photography Tips #10

January 5, 2022 Anthony Leave a comment

All cameras manufactured in the last 30 years, with the exception of a few highly-specialized models, are capable of automatic focusing or “autofocus”.[1] Many camera models now include a range of options that can be used to optimize the autofocus effect for specific situations. This article will describe autofocus servo modes and area modes, and recommend the best choices for wildlife photographers.

Note: Different camera manufacturers use different terms to describe what are essentially the same capabilities. Because I am a Nikon user I will use Nikon terminology throughout.

On basic cameras like those in mobile phones, autofocus is always enabled. For bridge cameras, DSLRs and mirrorless cameras there is usually a switch so that users can choose whether to use automated or manual focus. Your lens or camera body should have a switch labelled AF-M or M/A-M. AF stands for autofocus and M for manual focus. Ensure that the AF-M switch is set to AF or M/A.

M/A, by the way, means that the autofocus is activated but you can override it manually. This is a useful option to have when your subject is obscured, for example by foliage. The autofocus system may have a hard time finding the desired point of focus. (Remember that modern autofocus systems are “smart” to a degree, but not smart enough to understand that you want to photograph the bird and not some random twig or leaf). If you have the option to do so I recommend setting the camera to M/A so you can override the autofocus when necessary.

Once autofocus is enabled, you activate the focus system by depressing the shutter release halfway or, if you are using back-button focus, depressing the AF-On “back-button.”

There are two key sets of choices that you can make to optimize autofocus. Somewhat confusingly Nikon calls them Autofocus modes and Autofocus area modes. For the sake of clarity I will refer to them as Autofocus servo modes and Autofocus area modes.

Autofocus servo modes

There are two basic choices here. You can either lock focus on a single point, or use a tracking capability that automatically refocuses as the subject moves.

AF-S: Single servo AF

… or “One-Shot AF” for Canon cameras: This system is primarily used for stationary or slow-moving subjects. It uses a single point at the centre of the frame. When the focus system is activated – by half-pressing the shutter release or pressing the back-button – the camera will achieve and lock focus on that point.

Key point. If the camera and/or the subject moves, even if you hold the shutter release halfway down, the camera will not refocus. So small movements can lead to out-of-focus or not optimally focused images.

Note that you can customize this function using the camera menu system. There are two main options: (a) the camera will record an image when you press the shutter release (whether it is in focus or not), or (b) the shutter will not release if the image is not in focus.

Cunning photographers (I’m looking at you Phil) have learned that you can use option b to your advantage when photographing small, fast-moving birds. If you track the bird while holding the shutter release down, an image will be recorded at the fleeting moment when the camera has the bird in focus.

AF-C: Continuous servo AF

… or AI Servo in Canon-speak: This mode is optimized for moving subjects, and is the optimal choice for moving targets. While the focus system is activated the camera will continuously refocus until the shutter is released.

Key point. With AF-C activated, when you press the shutter release the camera will attempt to record an image whether it is in focus or not. So you do need to wait a moment for autofocus to find a solution. This wait time ranges from very short (less than a second) with high-end lenses at wide aperture, to several seconds with basic telephoto lenses.

One drawback of AF-C mode is that sometimes it is not as precise as AF-S, so you have to watch carefully to ensure you don’t end up with slightly out-of-focus shots.

AF-A: Hybrid mode

This is a third option often seen on lower-end DSLRs. In this mode the camera switches between AF-S and AF-C depending on whether it thinks the subject is moving or not. AF-A is intended to give a beginner the best chance of getting a good photo. The mode is not present on higher-end camera bodies because the manufacturer assumes that users will not want to cede control of such an important decision to the camera.

So to summarize, AF-S is best for stationary targets, and AF-C for moving targets.

To choose the autofocus servo mode you should consult the manual for your camera. Nikon DSLRs are controlled by depressing the AF button on the front of the camera and then moving a control wheel until the right symbol appears in the viewfinder.

Autofocus area modes

These options allow you to choose how the focus point is selected. In the Nikon world there are up to ten options depending on your camera body. But don’t despair: only a few of these are really useful for wildlife photography.

Pinpoint
Single point
Dynamic area modes (x4)
3D tracking
Face detection
Group
Auto-area

Pinpoint

This is a unique-to-Nikon mode that allows precise focus on a very specific point of the target. At the moment only the D850 DSLR and the Z6 and Z7 mirrorless cameras have this feature. It is not likely to be useful for wildlife photography in general, particularly since it is relatively slow to achieve focus. But it is worth considering for specific outdoor applications, e.g. macro photography of flowers, mosses and stationary (i.e. dead) insects. Note that it is only available with AF-S mode.

Single point

This is one of the most important modes for wildlife. The camera focuses on a single point at the middle of the frame. This is the fastest and most accurate of AF modes, and is particularly good for the following situations:

when you have time to compose a shot (and are using back-button focus activation). This mode allows you to zero in on the most important feature – usually the eye of the subject, and then recompose the shot knowing that the focus will remain on the chosen point. This is ideal for large mammals and birds, frogs, turtles etc that are close to the observer.
when the lighting is poor (explanation later in this article)
when your target is distant and there is a chance that using an area mode (described below) will lead to inadvertently focusing on a nearby twig or stalk of grass instead of the target

9-point Dynamic area

25-point Dynamic area

72-point Dynamic area

153-point Dynamic area

The idea of these dynamic area modes is that you can choose your focus point, and then as the subject moves the camera will “dynamically” keep the subject in focus. This is a very useful capability for photographing birds in flight, as long as you are aware of one limitation. If you wish to choose a specific initial focus point you do so by cycling between available points using a joystick or a rocker wheel on the back of the camera body. Professional photographers apparently perform this juggling act but mere mortals such as myself have enough issues to deal with in tracking a fast-moving bird without trying to manually move the focus point at the same time. Perhaps the professionals are photographing slower birds… 😊

On top of that, in order to use the joystick or rocker switch with my thumb I would have to re-route focus control from the back-button back to the shutter release, and I am unwilling to give up on the advantages of the back-button.

Camera controls – Nikon D850. Note that the rocker switch is in the locked position.

However if you are happy with a random focus point these modes work well. The Sandhill Crane below was taken using 25-point dynamic area mode. These birds were landing in waves at the Lost Mountain wildlife reserve in Saskatchewan and each group passed over very quickly. At my skill level there was no scope for picking a specific focus point but the autofocus mode did a good job selecting a usable one. (FYI I believe it is the left wingtip of the second bird). There is sufficient depth of field at f/8.0 that I’m not sure the image would have been improved if I had chosen a specific focus point.

Caveat

One thing to note is that the dynamic modes with larger numbers of focus points take slightly longer to achieve focus, and have an increased chance of focusing on something other than your desired subject.

But overall the dynamic modes are useful tools that are worth familiarizing yourself with. In order to use them the autofocus mode needs to be set to AF-C.

BTW the equivalent Canon term for Nikon’s dynamic modes is AF Point Expansion.

3D-tracking

This mode is a clever bit of technology. Once you have picked a focus point it analyzes colour differences to determine which object you want to focus on, and then uses as many focus points as necessary to keep that moving object in focus. I have not experimented much with this mode but sources I trust suggest that for birds in flight it works well against a clear background such as the sky, and less well when the background is busy. For large mammals, which are generally slower moving, this mode probably works very well. And another source reports that in a large mass of fast moving birds this mode is very good at picking out one bird and tracking it. 3D tracking mode is also only available in AF-C.

Face detection

This mode is self-explanatory. It is very useful for people photography but not really geared towards wildlife.

Group

This mode is one that I use frequently. When aimed at a group – e.g. a small flock of birds – it will focus on and track the closest member of the group. It uses only the centre point and the four others that are close to centre so it achieves focus quickly and holds it well.

Auto-area

This mode takes control of the focusing process and guesses what you wish to focus on. It seems to be intended for neophyte users who want to automate the whole photography process, so that their only responsibility is to point the camera in the general direction and hope for the best. I have not tried this mode but I understand that it is fairly good at finding faces. Otherwise it tends to focus on the nearest object. This mode is not really relevant to the wildlife photographer.

Recommendations

My first recommendation is that if you want to take full advantage of the capabilities of your camera you should learn how to change AF modes and AF area modes quickly and efficiently.

In my view the most useful AF combinations for wildlife are:

For stationary targets , especially if they are distant and/or the light is poor, use AF-S/single servo mode and a single (centre) focus point. Focus on the key feature (usually the closest eye). If you are using back-button focus you can then recompose without refocusing.

For all moving targets, use AF-C mode and one of the autofocus area modes.

Of these, I would experiment with 3D tracking for slow-moving targets (large mammals, e.g.).

For faster-moving targets, use either Group or one of the dynamic area modes. Of these I would stick to 9 or 25 point for most situations.

When I am out birding I will normally have the camera set at AF-C and 25-point area mode as this gives me the best chance of getting onto a fast-moving bird.

A note on low-light photography

Autofocus systems use areas of contrast to judge focus. If there is not enough detail (clearly defined edges) in the subject then the autofocus system will “hunt” – that is, cycle back and forth trying to establish a focus point. This explains why autofocus doesn’t work well in low light conditions – there is not enough contrast to achieve focus. So though your high-end DSLR can capture an image at astonishing ISO values, you will probably have to focus manually or accept blurry images. Or check your manual to see if your camera has an AF-Assist function that can help out.

The Blue Bill

This article originally appeared in the Blue Bill, the journal of the Kingston Field Naturalists, Volume 68, Number 4, December 2021.

[1] The term is a bit of a misnomer because it’s not really automatic – you still have to activate the autofocus system, or at least ensure that it is focusing on what you want it to.

Photography, Wildlife, Wildlife Photography

DEPTH OF FIELD – Wildlife Photography Tips #6

August 10, 2021 Anthony Leave a comment

How to adjust depth of field to improve your images. This article was originally published in The Blue Bill, the journal of the Kingston Field Naturalists.

In my early days as a wildlife photographer I was happy just to get a shot of the birds, beasts and insects I came across. But it wasn’t long before I started wanting to take better photographs. Looking back critically at images from a few years ago I found that some of my photos, particularly of birds and butterflies, were not as fully in focus as I wanted them to be. It was time to get a better handle on depth of field.

Depth of field is a relatively simple concept. Basically, it’s the area in a photograph where objects are acceptably sharp. Aside from exotic specialist equipment, cameras can only focus on one point. That point, and anything else at the same distance from the camera, can be precisely in focus, but anything nearer or farther will be less than optimally focused.

That’s where “acceptably sharp” comes in. Because the reduction in sharpness happens gradually, there is a range within which objects are sharp enough that they appear to be in focus. The range between the nearest and farthest objects that are acceptably sharp is called the depth of field (DOF). So as long as your subject is within that range all will be well.

(Note that apparent sharpness changes when an image is printed in a larger format, or when the observer is closer to the image, so an image that is acceptable sharp in 5×7” format may not be when blown up to 16×20”).

Why should I care about depth of field?

Landscape photographers obsess about getting maximum depth of field, and they use highly technical concepts such calculating hyperfocal distance to work out the optimal DOF. Depth of field preview functions, available on some camera models, are also used primarily in landscape photography. Fortunately we as wildlife photographers don’t need or have time to delve into those issues because our targets are constantly moving.

For us there are two main reasons to consider depth of field: to ensure that the whole target bird, turtle or butterfly is in focus, and to make an artistic choice about how much of the background should be in focus.

So back to the challenge of getting better images. I noticed that some of my photos of birds and butterflies had insufficient depth of field: typically in images of birds taken at close range the tails would be out of focus, and for butterflies one antenna was in focus but the other one was not. (See examples below).

Depth of field - Broad-winged Skipper — Broad-winged Skipper. Right antenna out of focus.

Broad-winged Skipper and *Virginia ctenucha*. One insect out of focus.

To address this issue, we need to understand the two main factors that influence depth of field: aperture size and proximity to the subject. Larger apertures reduce depth of field, as does moving closer to the subject.

If you are interested in the technical explanation for why this is so, a search of the internet will bring up multiple sources. I recommend you start with Wikipedia or Cambridge in Colour. But I believe it is not necessary to understand the physics as long as you understand the effect.

Aperture

Before we begin this section let’s refresh our memories about apertures. The aperture governs the amount of light passing through the lens. Larger apertures (bigger openings) are expressed by smaller numbers. Thus f/2.8 is a large aperture, and f/11 is a small aperture. Again, you can read up on the technical reasons for this or you can just remember the differences and move on.

The images below show the differences in depth of field as aperture size changes. Notice that the point of focus (the cocktail glass) remains constant, but the objects behind it start to become fuzzy as the aperture increases (i.e. the aperture number becomes smaller).

Proximity

While increasing the aperture (changing to a lower f stop) reduces DOF in a linear manner; increasing your proximity to the subject reduces DOF as an inverse square law. So as you get closer to your subject DOF decreases radically – a major challenge for macro photography.

Butterflies and odonates present a special challenge. Because they are small the temptation is to get as close as possible. But that is where the inverse square law comes into play – get too close and your DOF will be so shallow that parts of the insect will be outside the acceptably sharp range.

So how do I fix this?

The Canada Jay photos below show DOF in action. The birds were close (the images are uncropped) and there was not a lot of light available. Image 8 is taken at an aperture of f/6.3 and the tail is not acceptably sharp. Image 9, taken one half stop up at f/7.1 is noticeably better. So in principle, when taking photos of close-in subjects a higher than normal f stop (i.e. a smaller than normal aperture) is recommended. For more distant subjects a mid-range aperture should suffice.

Depth of field - f/7.1 — Canada Jay at f/7.1

As a rule of thumb if there is enough good light available, apertures in the f/7.1 to f/8 level should give you a good chance of capturing all the details of a bird that is relatively close.

For butterflies and odonates, a search through my files shows that in general I got better images from remaining bit farther away, using a smaller aperture and letting my telephoto lens do its job.

Depth of field - f/8 — White Admiral at f/8

If your subject is cooperative, remember that a key advantage of digital cameras is that you can check your images on the camera’s monitor and see immediately whether the depth of field is correct.

DOF and artistic composition

Having made the case that ensuring adequate depth of field is important, let’s now look at a situation where you may want to limit DOF. Many sports and wildlife photographers subscribe to a fetish that background detail is to be avoided at all costs as they claim it detracts from the subject. In general I believe that wildlife is best depicted in its environment, and that means there should be background detail – an animal is not an icon to be shown detached from the ecosystem it inhabits.

However there are situations where the background detail would not add any value – perhaps it’s too far away to be sharp regardless of the aperture setting, or perhaps the background is an unattractive pile of random scrub. In those cases choosing a field deep enough to just cover the subject can create an attractive effect. The Savannah Sparrow in the image below was perched on a fence with nothing behind it but long grass. In this case an aperture of f/5.6 was enough to ensure that the bird, the wire and the one leaf below it are sharp, while the background is a sea of formless colour.

A fairly distant Hooded Mountain Tanager in its environment. f/5.6

Depth of field - Savannah Sparrow — Savannah Sparrow f/5.6

Camera management for depth of field

So… let’s imagine that I have convinced you that depth of field is a thing you should consider. How should you go about controlling it?

The first step is to confirm how your camera displays the critical information: aperture, shutter speed and film speed. This information is probably displayed in your viewfinder and/or on an information panel. Check your manual to be sure, and then make a habit of keeping an eye on the aperture setting.

Modes

If you use the Programme or Automatic mode it suggests that you are relatively new to photography and need some help from the camera so you can concentrate on the subject. There is no shame here – everyone starts out using an automatic mode and those who aren’t intent on getting the best possible images can happily stay in those modes. Just be aware that by leaving all the decisions to the camera you will have no control over depth of field.

Many of the more experienced photographers use one of the semi-automatic modes: Aperture Priority (shown on the mode selector as A for Nikon cameras and Av for Canons), or Shutter Priority (S for Nikon, Tv for Canon).

In Aperture Priority mode you control the aperture setting manually. The camera will make what it thinks are necessary adjustments by changing shutter speed and (if you enable Auto ISO) film speed. If you use this mode keep a close eye on the shutter speed. For wildlife (or plants if there is a breeze) you should use shutter speeds below 1/500 sec with extreme caution. Motion blur will ruin any image regardless of how well you have judged the depth of field. If you are in Aperture Priority mode and need more shutter speed you can select higher film speeds (ISO) until you reach a point where the camera boosts shutter speed to compensate.

In Shutter Priority mode you essentially give up control of the aperture setting. If there is not enough available light your camera will default to a wide open aperture setting regardless of what you might want to see from a depth of field perspective, though in fairness most of the affordable telephoto lenses have base apertures of f/5.6 or more so even wide open there will still be some depth to the image. Again, increasing film speed will eventually cause the camera to compensate by stopping down the aperture.

There is a way to balance all elements of the light triangle – aperture, shutter speed and ISO – yourself to ensure that you can make the best decision under the circumstances. It involves taking the plunge into Manual mode – a topic for a future post.

Some random final notes

If macro photography is your thing, one way to get around the issue of very shallow depth of field is to invest in a camera that allows focus stacking. This process involves taking a large number of images of the subject with the focus point moved slightly between each image. These images are then “stacked” using software to yield a single image that is in crisp focus from one end to the other. I have seen some amazing insect and flower images taken using focus stacking. One consideration, though, is that the subject has to remain completely immobile (which usually means it needs to be dead).
Smaller apertures lead to greater depth of field, but only up to a point. Using apertures of f/11 and above can bring diffraction into play. Without delving into the technical explanation, the bottom line is that diffraction can seriously degrade the sharpness of your image. So more isn’t always better.
The notion that telephoto lenses have inherently shallow depth of field is a common myth that is repeated by many supposedly expert sites. A more accurate statement is that telephoto lenses appear to have a shallow depth of field because of the distribution of sharpness. Telephoto lenses tend to have an even distribution of acceptable sharpness in front of and behind the focus point, whereas for wide angle lenses the bias is tilted to the areas behind the focus point. In landscape photography this is an advantage because it creates a more gradual fading away of sharpness towards the horizon. But the bottom line is that a given aperture (e.g. f/5.6) will give the same depth of field with any focal length of lens.
Finally, it is a fact that the size of the sensor on your camera affects DOF. Counterintuitively, the large sensor of a full frame camera will develop a shallower depth of field at a given f stop than a camera with a cropped sensor. This is an interesting factoid, but one that’s not particularly relevant to wildlife photography. If I were in the market for a new camera body I can think of a lot of factors that I would consider before I got down to that one.

Birds, Photography, Wildlife Photography

Post-Processing – Wildlife Photography Tips #5

September 11, 2020 Anthony Leave a comment

In the previous post of this series I explained what happens in a digital camera – how a batch of photons is converted into a digital file. This post will cover how to use that file to create an image which can be displayed electronically or printed. This activity is called post-processing, because the initial processing of the image is done by software within the camera.

For wildlife photography, I believe the aim of post-processing is to produce a final image that replicates what you saw as closely as possible. And by “what you saw” I mean what you saw with your eyes through your binoculars, and not what the camera thinks you saw. Modern cameras are extremely capable, but their abilities are vastly inferior to those of the eye, especially the eye aided by precision optics. Occasionally the camera will manage to capture an image exactly the way you wanted it, but most of the time, especially in wildlife photography, the raw material produced by the camera will need some help.

The above images show the out-of-the-box version (Dusky Antbird 1) and the final version after post-processing (Dusky Antbird 2). Which would you prefer?

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Category Archives: Wildlife Photography

Autofocus Modes – Wildlife Photography Tips #10