Beginner’s guide to understanding aperture in photography
Understanding aperture is crucial for travel photography, and it should be one of the first settings to understand and master. This article covers aperture in photography for beginners. If you’re looking to improve your skills and take better images, then this is a great place to start.
What is aperture?
Aperture is a measure of how wide the lens opening is. This, in turn, means that more or less light is being let in. The main thing to remember is that the lower the number, the wider the aperture.
A wide aperture lets in more light to the sensor than a narrow aperture. A wide aperture also reduces the depth of field in comparison to a narrow aperture which has a wide depth of field. I explain this in further detail later in this post.
Aperture terminology
When it comes to aperture in photography for beginners, the terminology used to describe aperture can be overwhelming and confusing.
To put it simply, aperture is measured in f-stop numbers (f-number) but is often referred to using other terms. The f‑number is the focal length divided by the entrance pupil diameter.
Typical terminology relating to aperture adjustment includes:
- Wider aperture:
- Lower f-stop or f-number
- Large aperture
- Shooting wide open (lowest possible f/stop or f/number)
- Narrower aperture:
- Higher f-stop or f-number
- Smaller aperture
- Stopping down
How to adjust the aperture & aperture priority mode
Both DSLR and mirrorless cameras (crop and full frame) have a dial which can be used for adjusting the aperture. Many cameras have two of them: to adjust the aperture and shutter speed independently (when in manual mode).
Gear: Nikon D7200 + Nikon 35mm f/1.8. Settings: 1/160s at f/11, ISO 100, 35mm
As described in the post on best camera settings for travel photography my preferred camera setting is aperture priority. For Nikon & Sony this is “A” and for Canon, it’s “Av”. This allows control of the aperture letting your camera control the shutter speed to achieve the correct exposure.
Pairing this with Auto ISO gives control of the ISO based on a pre-set minimum shutter speed. This ensures a well-exposed image by automatically increasing ISO when the pre-set minimum shutter speed is reached. This approach is especially useful in changing lighting conditions.
Regarding aperture adjustment, the wheel usually controls the aperture in 1/3 stop increments, as shown on the right hand of the table below. A full stop change in aperture lets double (or half ) as much light through the aperture while also impacting the depth of field.
The table below shows the increments of full stop and 1/3 stop and explains why the gap between these stops widens as the aperture increases. The reason is that it’s a geometric sequence of numbers which ensures the area of the entrance pupil is double for each stop. This is done by using powers of the square root of 2, as shown in the table below.
| Full stops | 1/3 stops | Powers to √2 & exact number |
|---|---|---|
| f/1.8 | ||
| f/2 | f/2 | √22 = 2 |
| f/2.2 | ||
| f/2.5 | ||
| f/2.8 | f/2.8 | √23 = 2.828427125 |
| f/3.2 | ||
| f/3.5 | ||
| f/4 | f/4 | √24 = 4 |
| f/4.5 | ||
| f/5 | ||
| f/5.6 | f/5.6 | √25 = 5.656854249 |
| f/6.3 | ||
| f/7.1 | ||
| f/8 | f/8 | √26 = 8 |
| f/9 | ||
| f/10 | ||
| f/11 | f/11 | √27 = 11.3137085 |
The impact of aperture on depth of field
The main impact of the aperture is on the depth of field and the amount of light reaching the sensor. This controls the distance between the closest and farthest objects in a photo that appears in acceptable focus. One of the best ways to see the impact is to try it with your own camera, lens and subjects. There is also a range of online tools, such as the Depth of Field Simulator.
When to adjust the aperture
Camera modes for “portrait” or “landscape” modes basically change the aperture as the key setting. Simply put, a narrow aperture for landscape and a wide aperture for portraits, therefore controlling the depth of field.
Adjusting the aperture ensures landscapes are in focus and portraits isolate the subject from the background. Of course, with this change in aperture comes a need to change the ISO and shutter speed to create a balanced exposure as the aperture controls the amount of light hitting the sensor.
Gear: Nikon D3200 + Tamron 16-300mm f/3.5-6.3. Settings: 1/125s at f/6.3, ISO 450, 300mm
Lenses and aperture
Typically, the wider the size of the aperture the more expensive the lens. This is especially the case for long focal length lenses as the f-number = focal length/entrance pupil diameter. Therefore to maintain a low f-number at a long focal length, the entrance pupil diameter needs to be very large, leading to a large, complex, costly lens.
I demonstrate it in the chart below showing prime lenses of varying focal lengths, with their aperture and cost. The highest-cost lenses have wide apertures and length focal lengths. For a 500mm lens, the cost increase for an increase of 1 stop (f/4 in comparison to f/5.6) is £6500! For a professional wildlife photographer, this may be essential, given the associated image quality benefits with this pedigree of lens. However, for beginner photographers, this wouldn’t be recommended or required.
Luckily for long focal lengths, there are cheaper (but still costly!) alternatives, which have narrower apertures but come with zoom capability. Such as the Nikon 200-500 f/5.6 or Tamron 150-600mm f5-6.3 or Sony FE 200-600mm f5.6-6.3 for mirrorless.
Gear: Nikon D3200 + Nikon 35mm f/1.8. Settings: 1/3200s at f/2.5, ISO 100, 35mm
The chart above also applies to zoom lenses where your “holy trinity” f/2.8 14-24mm, 24-70mm & 70-200mm will come at a high cost, size and weight in comparison to higher aperture f/4 or above alternatives.
“Holy Trinity” refers to three lenses which cover 14-200mm at a wide constant aperture of f/2.8.
The chart above also shows how the shorter focal length prime lenses, with wide f/1.8 apertures, come at an accessible price point. These are great lenses for achieving a shallow depth of field for portraits or subjects closer to your camera. These are also small and lightweight making them perfect for travel if you’re comfortable without a zoom lens.
Gear: Nikon D3200 + Nikon 35mm f/1.8. Settings: 1/80s at f/2.0, ISO 100, 35mm
Impact of distance from your subject and focal length on depth of field
If your subject is far from your camera, then you can usually use wide apertures while keeping everything in focus. For example, a landscape photo below is shot without a foreground element close to your camera. This means that you don’t always need a narrow aperture to ensure the whole scene is in focus. It very much depends on your composition. Shooting at a lower aperture will allow you to maintain a higher shutter speed and lower ISO, which could eliminate the need to use a tripod for some scenes.
Gear: Nikon D3200 + Nikon 18-55 f/3.5-5.6 Settings: 1/125s at f/5.6, ISO 250, 55mm
An extreme example would be astrophotography where a low aperture is required to let in enough light, as the stars are so far from your camera, there are no issues related to depth of field.
Gear: Nikon D3200 + Tokina 11-16 f/2.8.
Settings: 20s at f/2.8, ISO 1600, 11mm (4 shot vertical panorama)
However, consider that your lens may not have optimal sharpness, in particular at the edges when used at lower apertures for landscape or astrophotography. Another key consideration for astro, is the focal length of your lens. Longer focal lengths require faster shutter speeds to prevent star trails, leading to higher ISO requirements even at your widest aperture. The Rule of 500 (or 300) helps to prevent this. Dividing 500 by your focal lengths gives an indication of the maximum shutter speed to prevent star trails. I’ve found 300 to also work well, for example, 11mm/300=27.2 seconds.
It’s best to consider the closest thing to your camera that you need in focus, and the furthest thing, and use this to decide on your aperture. This will also depend on your camera, focal length and lens, so it will take practice
Always get into the habit of checking focus after each shot when you’re changing settings. TOP TIP: Setting up a camera shortcut to zoom in at 100% can save you from pressing your zoom-in button many times to check focus! For my Nikon D7200 this is my “OK” button and it saves me a lot of time and gives me no excuse for out-of-focus shots.
Depth of field challenges
How low is too low when considering depth of field? If you’re looking to blur out the background behind your subject, then a lower/wider aperture is preferred. However, you need to consider your lens’s aperture, focal length, and the distance between your camera and the subject and the background.
There will be some instances when shooting wide open isn’t always best as the depth of field (DoF) will be too narrow. For example, if capturing a portrait of a person or an animal on your travels, you may want both eyes in focus. If both eyes are not the same distance from the camera and you’re close to your subject then a narrow depth of field may not allow both eyes to be in focus. To keep the same framing, a higher aperture is needed to increase the depth of field.
Gear: Nikon D3200 + Nikon 35mm f/1.8. Settings: 1/800s at f/1.8, ISO 100, 35mm
Even with landscape photography, a wide-angle lens with a narrow aperture may not be sufficient for a wide depth of field. A very wide DoF is needed for landscape shots which have the foreground close to the lens and the far elements in the distance.
Focus stacking of an image with the focus in the foreground together with an image with the background in focus may be the only way to capture the whole scene in focus.
To experiment with DoF, use the app PhotoPills. With inputs of camera, focal length, aperture & subject distance which will then tell you the depth of field.
Impact of aperture on image quality
Shooting wide open is rarely going to give you the best sharpness unless you’re using a top-of-the-range lens. Vignetting can also be an issue when using a lens wide open, but this can be corrected in post-processing if needed. Most lenses perform better stopped down, the optimal lens aperture for sharpness will depend on the lens used. As general best practices, the following apply:
- Lenses with a maximum aperture of f/1.8 or f/2.8 perform best at f/5.6 or f/8
- Lenses with a maximum aperture of f/4 or f/5.6 perform best at f/8 or f/11
It’s best to experiment with your own less to find the sharpest aperture.
When would you use a very small aperture?
If using a very small aperture, for example, f/16 or above any sensor dust spots on the sensor are more visible in the final image, especially against a clear sky. This can be more of a problem with mirrorless camera systems, which have the sensor exposed during lens changes. However, you can use this “issue” to your advantage to check your camera sensor for dust spots.
How to check your sensor for dust spots? Zoom into your longest focal length and stop down to the smallest aperture/highest f-number on your lens. Then take a photo of the sky. This image can be used to locate the dust spots on your sensor when zooming in 100%. After cleaning your camera’s sensor with the appropriate lens blower and sensor swabs the process can be repeated. Only clean your camera’s sensor if you feel comfortable doing so.
Which lens and aperture is best for you?
Below are some key travel photography genres, along with general tips for aperture settings.
Travel
Travel photography covers many of the genres below, and therefore requires flexibility in terms of lens selection for your given choice of aperture. Transporting large, heavy, long focal length wide aperture lenses isn’t always realistic. Therefore sticking with lighter with wide aperture prime lenses in the 50mm f/1.8 range is typically preferred.
For longer focal lengths, a super zoom lens with a narrower aperture can give the flexibility needed to capture a wide range of subjects. This type of lens comes with reduced weight, expense and size. Read more about the Best lenses for Nikon D7200 for travel photography which also applies to other camera models.
Street photography while travelling
For street photography, staying compact and lightweight is preferred, ideally with larger apertures of f/1.8 or f/2.8. Regarding focal lengths, a 24mm, 35mm or 50mm prime can work well.
Travel landscape/hiking photography
The last thing you want is to hike up a mountain for landscape photography with a bag full of heavy lenses. Therefore, lens selection needs to provide you with the flexibility needed to capture your intended photographs. A wide aperture isn’t often a must, which saves weight and space with your lens choice.
A wide-angle zoom and a telephoto zoom are normally a good combination to cover the required focal lengths. A versatile superzoom such as the Tamron 16-300mm could also replace both by covering the wide and long ends of the focal range. This is a lightweight, low cost and compact lens. The main comprises are a reduction in maximum aperture and image sharpness. Many people won’t even notice those.
A tripod enables for slower shutter speeds which are often needed in low light when combined with a higher aperture value to keep the full scene in focus.
The amount of kit landscape photographers are willing to hike with depends on the distance and elevation together with personal preference. In some instances, great landscape photography shots are possible from the side of the road. Some great locations in North Wales where this is possible are included in The Ultimate North Wales road trip.
Capturing wildlife while travelling
Wildlife is the one genre where a long focal length is almost a requirement. In some instances, it’s not possible to move closer to your subject. This comes with a high cost if looking for wide apertures and very long focal lengths. However, if you’re starting out a budget telephoto or superzoom can still work well. Consider the camera body as the narrow apertures on these cheaper lenses will need relatively high ISO to maintain adequate shutter speeds for freezing any fast birds or wildlife.
Using a crop sensor lens can also give a benefit over a full-frame camera body as the smaller sensor gives you a 1.5-1.6x crop factor. For travel, this is important as it allows the use of smaller, cheaper and lighter crop sensor lenses. This provides an equivalent field of view of a full-frame lens and camera combination. Even with a small aperture opening, it’s still possible to achieve a blurred background with long focal length lens compression.
TOP TIP: Make sure you increase the distance between your subject and the background. An easy way to achieve this with subjects on water or on the ground is to get low, at eye level with your subject.
Gear: Nikon D7200 + Tamron 16-300mm f/3.5-6.3 Settings: 1/400s at f/6.3, ISO 500, 220mm
Sports/action
Sports and action have similar requirements to wildlife photography. However, the need for a faster shutter speed and long focal lengths both in low lighting conditions puts even more emphasis on the need for the largest aperture lens you can afford. Without wide-open apertures, it can be a challenge to maintain high enough shutter speeds or avoid noise at high ISO.
Capturing portraits while travelling
A general rule of thumb is wide apertures are needed to isolate your subject from the background by giving a narrow depth of field.
Portrait photographers typically use longer focal lengths which help remove any distortion effects producing more flattering images in comparison to wider angle lenses. For full frame cameras, this is typically an 85mm f1.8 or 70-200mm f/2.8 and for crop camera sensors a 50mm f/1.8.
TOP TIP. To achieve a shallow depth of field in any of these genres (and the associated Bokeh/ background blur) consider the following aspects:
- Use the widest aperture your lens offers
- Use your longest focal length
- Increase the distance between your subject and the background
- Reduce the distance between you and your subject
Of course, your lens choice and optimal aperture for your situation depends on personal preference. The above are only recommendations to help guide your choices if you’re new to photography.
FAQs
Generally, if you want more of the scene in focus, use a smaller aperture (higher f-stop number) to increase your depth of field. With a higher f-stop number, less light will reach your camera sensor. Therefore consider the exposure triangle by decreasing the shutter speed or increasing the ISO (sensitivity of your camera sensor) for good exposure.
If you want to put emphasis on your subject and blur the background, use a larger aperture (lower f-stop number) to reduce your depth of field. With the larger aperture size at these f-stop values, you may need a fast shutter speed to avoid overexposure.
For beginners, it’s best to apply general best practices for setting your aperture. Low (or wide) aperture for portraits or where you would like a blurry background around your main subject. For scenes where you have enough light, use a higher number f-stop. It will reduce the amount of light entering your camera and increase your depth of field. This will ensure more of the scene is in focus. If you’re a beginner don’t take it to the extreme on the lower or upper aperture range as you may risk out-of-focus images on the lower end, and insufficient light at high numbers.
Unless you’re confident with your focus point position a very narrow depth of field (low or wide aperture) will be a challenge to ensure the correct area is in focus. Stop down, or use a higher f-stop number. A higher f-stop number will ensure more of the scene is in focus. It, in turn, reduces the risk of your subject being out of focus. This is especially important for lenses with low maximum apertures.
A smaller f-stop number creates a small opening which lets less light into the camera. This increases the depth of field which is the term used to describe the amount of the image that will be in focus in front and behind your focal point. This is your preferred option to get the whole scene in focus. As a starting point aim for f/8 to f/11.
