Lens Basics #9: Large Aperture Lenses
With their small f-numbers, large aperture lenses not only make it possible to achieve a creamy background blur effect, they also have a number of other advantages. Read on to find out more. (Reported by Tomoko Suzuki)
Characteristics of large aperture lenses
1. The large maximum aperture makes it easy to achieve creamy bokeh (background blur).
2. They let you shoot with a fast shutter speed even in low light conditions—good for preventing camera shake.
3. The extremely shallow depth-of-field requires more effort to ensure tack-sharp focusing.
4. They give you a brighter, clearer view if you are using an optical viewfinder.
Large aperture lenses are also known as large diameter lenses due to the relatively large size of the “opening” that allows light into the lenses. The larger opening gives the lens a large maximum aperture (small f-number), and are also why such lenses are also often called “bright” lenses. They generally have a maximum aperture of f-number f/2.8 or smaller, although on a variable aperture zoom lens, this maximum aperture depends on the focal length used. The larger the maximum aperture, the easier it is to obtain a prominent background blur effect.
The large amount of light that is able to enter the lens and reach the image sensor due to the large aperture means that it is possible to maintain a fast shutter speed even in low light conditions, such as when shooting indoors, at night, or in dim lighting. This helps to prevent camera shake, even when shooting handheld.
However, large aperture lenses also have an extremely shallow depth-of-field, which can make it difficult to establish precise focus. For some scenes, it might be more effective to shoot in Live View using a magnified display and manual focusing (MF). (Read: How Do I Focus Accurately With Manual Focus?)
On cameras that use an optical viewfinder, such as the EOS 77D and EOS 800D, large aperture lenses provide an additional advantage—they allow more light to enter the optical viewfinder, which results in a clearer, brighter view. This is especially beneficial for establishing focus and composing shots in low light conditions.
Main types of large aperture lenses
IS lenses for full-frame cameras
Non-IS lenses for full-frame cameras
Canon’s large aperture lenses can be divided into three categories:
IS lenses for full-frame cameras have built-in image stabilization (IS), which makes them even more effective for shooting in low light conditions, and also for shooting handheld.
Non-IS lenses for full-frame cameras are more effective in low-light scenes compared to “darker” lenses with smaller maximum apertures.
EF-S/EF-M lenses are made for use with DSLR cameras with APS-C sensors and EOS M-series mirrorless cameras respectively, and are capable of creating creamy bokeh.
There are large aperture lenses that are prime lenses, and those that are zoom lenses.
What makes a lens “large aperture”?
In general, a lens can be considered a “large aperture lens” if its smallest f-number (maximum aperture) is f/2.8 or below. Using this maximum aperture allows you to achieve an intense defocus effect (bokeh) and fast shutter speeds in dim or dark conditions, among other advantages.
Techniques to make the most of your large aperture lens
1. Use a small f-number to create pretty bokeh circles
EOS 6D/ EF50mm f/1.8 STM/ FL: 50mm/ Aperture-priority AE (f/1.8, 1/4 sec, EV-0.3)/ ISO 100/ WB: Daylight
EOS 6D/ EF50mm f/1.8 STM/ FL: 50mm/ Aperture-priority AE (f/5.6, 2.5 sec, EV-0.3)/ ISO 100/ WB: Daylight
2. Use Aperture-priority AE mode to control the size of the background blur
If you want to make use of bokeh (background blur) in your composition, use Aperture-priority AE mode and set your preferred aperture setting. If you use Program AE mode, the camera will automatically set the f-number, which will not necessarily be the maximum aperture.
Program AE (f/3.5, 1/60 sec)
EOS 5D Mark III/ EF50mm f/1.4 USM / FL: 50mm/ Program AE(f/3.5, 1/60 sec, EV+0.7)/ ISO 100/ WB: Daylight
Aperture-priority AE(f/1.4, 1/250 sec)
EOS 5D Mark III/ EF50mm f/1.4 USM/ FL: 50mm/ Aperture-priority AE(f/1.4, 1/250 sec, EV+0.7)/ ISO 100/ WB: Daylight
Large aperture lens work best in these scenes!
EOS 5D Mark III/ EF50mm f/1.2L USM/ FL: 50mm/ Aperture-priority AE(f/2, 1/50sec, EV+0.7)/ ISO 640/ WB:Auto
When you want to isolate a main subject
With a large aperture lens, you can create a large background blur even if the main subject is only a short distance away from the background. This is great for when you want to make one particular object stand out in an image with a few elements. You might find yourself using this technique very often when photographing food, objects around you, or even portraits!
EOS 5D Mark III/ EF85mm f/1.2L II USM/ FL: 85mm/ Aperture-priority AE(f/1.2, 1/100sec)/ ISO 500/ WB:Auto
When you want to take handheld shots at night
When there is very little light, you usually need to expose your images for slightly longer so that they will not turn out too dark. Doing so increases the chances of camera shake, which photographers usually try to prevent by using a tripod. However, with a large aperture lens with its large maximum aperture, more light can enter the lens and camera. This lets you shoot handheld even at night, without having to bump up the ISO speed to compensate.
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Digital Camera Magazine
A monthly magazine that believes that enjoyment of photography will increase the more one learns about camera functions. It delivers news on the latest cameras and features and regularly introduces various photography techniques.
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After graduating from the Tokyo Polytechnic University Junior College, Suzuki joined an advertisement production firm. She has also worked as an assistant to photographers including Kirito Yanase, and specializes in commercial shoots for apparels and cosmetic products. She now works as a studio photographer for an apparel manufacturer.