Aperture and Auto ISO – 2 settings which will instantly make your wildlife photography easier.

Immediately see a big difference in your images using these 2 settings. 

  • Aperture Priority
  • Auto ISO (minimum shutter speed 1/1000s)

Extract taken from my book The Ultimate Beginners Guide to Wildlife Photography – from taking a shot to capturing a moment


What is Aperture?

Aperture is one of the photography basics and, along with the ISO and shutter speed, one of the three components of the “Exposure Triangle.”

But aperture doesn’t just affect the exposure, it also plays a key role in other photography aspects, such as the depth of field, the sharpness, and generally the final result of your image.

Aperture in photography is the opening of the camera lens, which is related to the amount of light that passes through the camera lens to the image sensor.

The aperture mechanism in the lens that allows more or less light to come in is formed of a series of opaque “blades” called a diaphragm. When the blades are open, your camera sensor will capture more light, whereas as the blades progressively close, less light will hit your sensor.

Aperture Diagram in wildlife photography

A large aperture is a wide opening of the lens, which allows it to capture more light.. When you use the largest aperture in your lens, you’re using a “wide-open” aperture. The lower the number the wider the aperture. Eg F2 or F2.8

A small aperture is the opposite: a narrow opening of the lens blades that doesn’t allow the passage of much light. The higher the number the smaller the aperture. Eg F16 or F22

Aperture in photography can be explained in a similar way to our eyes, since it works like the human pupils: the wider they are, the more light will pass through and vice versa.

One of the best photography tips for beginners is to understand what the aperture is through practical exercises in which you vary this setting in manual mode.

Aperture and Exposure

Aperture affects exposure and plays an important and crucial role in determining, along with the ISO and shutter speed, the optimal exposure in an image.

With a fixed ISO and shutter speed, the wider the aperture (or lower F-values), the brighter your image will be, and the narrower your aperture (higher F-values), the darker it’ll be. Large apertures are also known as fast apertures since they allow you to decrease the exposure time, and small apertures are also known as slow apertures, since they allow you to increase the exposure time.

Aperture and exposure in wildlife photography

Aperture and Depth of Field

The second most important aspect is the relation between aperture and depth of field.

The depth of field is the proportion of the image that is reasonably sharp and in focus.

According to the laws in optics, the larger the aperture you use, the shallower depth of field you’ll be able to capture, meaning more areas of your images will be out of focus and less sharp.

The opposite is also true, the smaller the aperture you use, the greater the depth of field you’ll see in your image, meaning a bigger proportion of the image will be in focus.

Aperture and depth of field in wildlife photography

The wider the aperture (lower the number) the less the image will be in focus The smaller the aperture (higher the number) the more the image will be in focus.

Aperture and Sharpness

Another crucial factor beyond the exposure and depth of field is how aperture affects sharpness in photography.

Using extreme aperture values in photography is not recommended. When you use a very large aperture, your lens can’t physically produce the sharpest results, since the diaphragm will be wide-open, trying to capture as much light as possible.

That way, as you open your aperture below f/5.6 values, you’ll be able to notice how your image loses sharpness.

This is not however as much of an issue in higher end lenses with most prime and top of the range zooms retaining sharpness throughout the range.

To calculate this sharpness sweet spot roughly, move two to three F-stop values from the maximum aperture of your lens. For example, if the maximum aperture in your lens is f/4, this would be between f/8 and f/11

Applying this to Wildlife Photography

Traditionally, wildlife photographers tend to shoot ‘wide open’, which means using the widest possible aperture.

There are a number of reasons for this:

  • The lower depth of field means that the object is nicely ‘separated’ from the background, which might otherwise be a distraction.
  • More light falls on the sensor, which reduces noise and allows a faster shutter speed for action shots or in low light.
  • The background blur – or ‘bokeh’ – will be softer, and any blurred highlights will be rounder rather than pentagonal or octagonal.

As a result, it’s a big advantage to have a ‘fast’ lens as the maximum aperture will be wider than normal.

A typical long lens will have a maximum aperture of f/5.6, but as discussed in the previous section you can pay more to get it down to f/4 or even f/2.8.

Using a wide aperture in wildlife photography

Shooting at low apertures makes the subject stand out from the background and creates a beautiful creamy bokeh.

That being said why would you want to shoot at higher apertures?

There are a few reasons below:

  • To capture more than one subject at different distances from the camera (ie on different ‘planes of focus’).
  • To give yourself more leeway when taking action shots in order to be sure of getting a sharp result.
  • To give lots of depth of field when taking an ‘environmental portrait’
  • When shooting portraits of animals with long noses face on. If you don’t have enough depth of field then the eyes will be in focus but the nose out of focus.

Using a small aperture in wildlife photography

Aperture Priority Mode

Aperture Priority or “Av/A Camera mode” is a camera priority mode and it’s also considered a semi-automatic Camera Mode.

When you select the Av or A setting on camera, you’ll select the aperture and the camera will automatically set the shutter speed to match a balanced exposure. If you use a wide aperture, your camera will select a faster shutter speed, whereas if you use a narrow aperture, your camera will set a slower shutter speed.

This camera priority mode allows you to have full control over the depth of field of your image, something crucial in the final look of your photograph.

Unlike the Shutter priority mode (Tv mode), Aperture priority mode usually provides better results, since the camera has barely any limitations setting the best shutter speed. That’s why this is one of the most popular camera modes in photography and a dial mode widely used by photographers.

This shooting mode is also available in all cameras and the abbreviation also depends on the manufacturer. The Canon Av Camera mode and the Nikon A camera mode are the most popular.

Auto ISO

Most modern DSLR cameras and Mirrorless cameras have the ability to set Auto ISO. What this means is that you can set a minimum shutter speed that you want the camera to select an ISO for. So for example if you wanted to guarantee the shutter speed at 1/1000 and the light keeps changing, then the camera will automatically select the lowest ISO possible to maintain your shutter speed of 1/1000.

What is so good about Auto ISO Setting? 

This camera mode allows me to have total creative control over the camera settings that influence the final appearance of my image. I determine what aperture will give me my desired depth of field; I then set the shutter speed depending on the conditions and my vision for the finished nature photo. The camera does the rest of the work – metering for exposure and setting an ISO that it deems appropriate. If I need to tweak the camera’s chosen ISO, I can.

There are 2 situations where I find Auto ISO Setting to be extremely useful.

  • Quickly Changing Light
  • Birds in Flight or other action sequences.

Quickly Changing Light

The first is when the light is changing quickly and the subject is moving. Because the subject is moving and you usually desire sharpness, You need to ensure that your shutter speed is high enough to freeze the subject. And, since I don’t want my aperture moving about, You can manually set both aperture and shutter speed. If using manual. Or set the Aperture If shooting on aperture priority. Without Auto ISO – you need to be conscious of the changing light and adjust the ISO as needed. It is so much easier to let the camera choose the ISO. You are then free to concentrate on composition and trying to capture that decisive, often elusive moment.

The images on the next page are 3 otter images – all taken in the space of an hour using Auto ISO – the Aperture was set and then Auto ISO was set to achieve a minimum shutter speed of 1/1000.

By doing this it eliminates the need to keep changing exposures and ISO. That way if the otter runs or moves, you have your shutter speed maintained.

Auto ISO in wildlife photography

Birds in Flight

For me using Auto ISO for birds in flight is a game changer. It simply means that If the bird fly’s  for example from against the bright sky down to tree level you don’t need to change the ISO. If you think that you may want an aperture of F8 and the shutter speed to be at 1/1000 Auto ISO can be set for this. If you are photographing smaller birds or faster moving birds then you can change the minimum shutter speed in the menu to 1/2000 or 1/3000 etc.

Auto ISO for birds in flight

Why I use Aperture Priority and Auto ISO

The Advantages of Aperture Priority and Auto ISO

I guarantee that a lot of experienced photographers and pros that read this will shoot in manual mode and will be ambassadors for manual. Some will say that you can’t be a “real” photographer if you don’t shoot in manual.

I started like most people on program, then I switched to shutter priority, then I learnt to shoot using manual, but for the last 15 years I have shot in aperture priority and here is why:

The process I go through is simple.

  • What image do I want to create?
  • Do I want a blurred background or foreground?
  • How much of the subject do I want in focus?
  • How fast do I need the shutter speed to be?
  • How much available light do I have?

Aperture priority is popular in landscape photography because of the control that you can have with depth of field. This is important to me in my wildlife photography and I try to use this when I am considering the images that I want to create.

Depth of field has a dramatic effect on the look of your images. Often, as wildlife photographers, we will want a nice, soft background. This is possible with a shallow depth of field – created with a low f-number – and it is not helpful for the camera to be changing this value itself. Therefore, Aperture mode lets you take control of that.

So if I want a bird sat on a perch with a blurred background. I will shoot wide open. By setting the aperture for example at F4 then the camera will select the relevant shutter speed. If I want the background to appear more in focus for example as more of an environmental shot, I will close the aperture down.

Also, photos of birds in flight will require a larger plane of focus to ensure the entire wingspan is in focus – as well as giving some degree of margin for error. So in this scenario you would shoot at around F8.

By selecting the aperture you also have complete control over the shutter speed. If you shoot on the widest aperture the camera will select the fastest shutter speed available.

Aperture mode does not have a limiting factor when adjusting the shutter speed. Your shutter speed can always get slower, and it is fairly obvious when it is so slow that you will be getting motion blur.

The sound of a slow shutter is obvious, and when you hear it then you know to increase your ISO speed to maintain a fast enough shutter speed.

The beauty of Aperture mode is that your images will always be correctly exposed; the camera can always let in more light. Manually adjusting the ISO speed, as well as using the exposure compensation dial, allows you to fine-tune the settings that the camera chooses for you.

Over the last few years I have also been using Auto ISO as well. I have mentioned this in earlier sections, but If you dial in your minimum shutter speed as what you want to eliminate motion blur – you can keep controlling your aperture for the creative element and the camera will set the shutter speed as high as possible, If the light changes the camera will increase the ISO to maintain a minimum of the shutter speed you selected.

Aperture priority is simple and quick to use and enables me to concentrate on my composition and capturing behaviour and the images that I want to without constantly messing about and changing settings.

In wildlife photography you often have a split second to capture a moment, you are often working constantly in changing light.

Aperture priority just simplifies the process with minimal adjustments and ensures that you are always ready.

In summary:

Every time I go out to do any wildlife photography, before I even leave the house I always set my camera up the same way. It is always set up to capture action and behaviour. Everything always happens very quickly and when you need to be ready to capture a moment you need to be confident in the settings that you have. You can then adjust the settings accordingly to capture portraits and be more creative if the situation arises.

Camera Settings

ISO – Set to Auto ISO. Minimum Shutter Speed 1000

Camera Mode – Aperture Priority. Set at F4 (Wide open) will always mean that I get the fastest shutter speed possible.

Focus Mode – Continuous Autofocus. Group Autofocus Mode

White Balance – Auto

Camera Metering Mode – Evaluative Mode

Camera File Mode – Raw

Camera Burst Mode – Burst not single shot.

These are always the settings I use when I start any session in the field. The settings are built for speed and action, they are set to capture movement.

If something happens quickly in the majority of situations you will be able to capture the type of images that you want.

If you are photographing something that moves quicker then you can change the minimum shutter speed in Auto ISO to 2500 for example.

If you want to be more creative you can always switch Auto ISO off to then enable you to select slower shutter speeds etc.

The correct settings alongside researching your subject and their typical behaviour will give you the edge when it comes to capturing wildlife images full of impact and drama.

Goshawk in the rain shot using Aperture Priority and Auto ISO     Beaver grooming shot with Aperture Priority and Auto ISO     Diving Kingfisher shot using Aperture Priority and Auto ISO

Serval Cat Jumping shot using Aperture Priority and Auto ISO     Red Panda shot using Aperture Priority and Auto ISO      Striped Hyena shot using Aperture Priority and Auto ISO

To find out more you can buy my ebook for just £2.99 on Amazon 436 pages packed full of images and tips on wildlife photography.

The Ultimate Beginners Guide to Wildlife Photography – from Taking a Shot to capturing a moment – buy it here

All Aperture diagrams used with permission from Capture the Atlas

If you like this post then why not check out my post on Understanding Angles of Light in Photography

Pin It on Pinterest

Share This