Lens Basics #2: Prime Lenses
Prime lenses, sometimes also known as fixed-focal-length lenses, are great for creating bokeh as well as taking pictures with minimal camera shake. Let’s explore the unique features of this category of lenses, and take a look at how their huge maximum apertures can benefit our images. (Reported by Tomoko Suzuki)
The biggest appeal of prime lenses: Great bokeh, easily
- Large maximum aperture, great for creating bokeh
- Lets you use a faster shutter speed in low light, which prevents camera shake
- Tend to be small, lightweight and therefore very portable
- Have to change lenses frequently to get different focal lengths
- Cannot zoom to adjust the angle of view
Prime lenses are also known as single focus lenses or fixed focus lenses. As those names suggest, they have only one focal length, so it is not possible to zoom in or out to change your angle of view. However, they also tend to be bright and come with a wide maximum aperture (small f-number), which makes it easy to create a good bokeh effect in the background. They also let you achieve a faster shutter speed when you shoot in low light conditions, so that you can obtain a clear image without having to use a high ISO speed and risking the occurrence of noise in order to prevent camera shake.
What's the relation between aperture, shutter speed and ISO speed? Here’s a recap:
Camera Basics #3: Exposure
Compared to zoom lenses, prime lenses have a simpler lens construction, which is also why they are usually smaller, lighter and more portable. This is yet another feature that differentiates them from zoom lenses. However, have a fixed focal length, for certain scenes and subjects, you may have to carry a few lenses around and switch lenses frequently to achieve your intended shot. As this also means that you have to rely on your own ability to compose your shots, you could also say that using prime lenses helps to improve your photography skills.
Key concept (1): Types of prime lenses
There are four main categories of prime lenses. The first consists of ultra wide-angle lenses (focal length shorter than 24mm at 35mm film equivalent) and wide-angle lenses, which can capture a wide area of a scene. The second category consists of standard lenses (50mm equivalent) and mid-telephoto lenses (85mm equivalent; also known as ‘portrait lenses’ because they are often used for shooting portraits), which can capture an angle-of-view that is close to that of the naked eye. Telephoto lenses and super telephoto lenses, which can capture faraway objects close-up, form the third category. Last but not least are the macro lenses, which can capture close-up images of tiny subjects from a close shooting distance.
Ultra wide-angle lens and 2 wide-angle lenses
(1) EF14mm f/2.8L II USM
(2) EF24mm f/2.8 IS USM
(3) EF-M22mm f/2.0 STM
2 standard lenses and a mid-telephoto lens
(4) EF-S24mm f/2.8 STM
(5) EF50mm f/1.4 USM
(6) EF85mm f/1.8 USM
A telephoto lens and a super-telephoto lens
(7) EF300mm f/4L IS USM
(8) EF600mm f/4L IS II USM
(9) EF-M28mm f/3.5 Macro IS STM
(10) EF-S35mm f/2.8 Macro IS STM
(11) EF100mm f/2.8L Macro IS USM
Key concept (2): Prime lenses, zoom lenses and the difference in bokeh effect
Prime lenses tend to be better for shooting images with bokeh compared to regular zoom lenses at the same focal length. The examples below were shot at 50mm. The maximum aperture available on the prime lens was f/1.4, while that of the zoom lens (at this focal length) was f/5. Note how this difference has significance on the size of the defocused area in the bokeh.
EF50mm f/1.4 USM
EOS 5D Mark III/ EF50mm f/1.4 USM/ FL: 50mm/ Aperture-priority AE (f/1.4, 1/1250 sec, EV±0)/ ISO 100/ WB: Manual
EF24-105mm f/3.5-5.6 IS STM
EOS 5D Mark III/ EF24-105mm f/3.5-5.6 IS STM/ FL: 50mm/ Aperture-priority AE (f/5, 1/125 sec, EV±0)/ ISO 100/ WB: Manual
Key concept (3): Range of selectable f-numbers
Prime lenses, especially those with a large maximum aperture, provide a wider range of usable f-numbers compared to a variable aperture zoom lens set to the same focal length. For example, the maximum aperture of the EF24-105mm f/3.5-5.6 IS STM at 50mm is f/5, but on the EF50mm f/1.4 USM, you can use f/1.4, its maximum aperture. Having a wider range of f-numbers to choose gives you more options in artistic expression.
Here’s what is possible with an f/1.4 lens:
Astrophotography: Capturing Clear Starry Skies with f/1.4 Lens
Key concept (4): Establishing focus
When you use a prime lens at its maximum aperture, the depth-of-field is shallow (i.e., the area that appears to be focus becomes very narrow), and this makes it harder to achieve focus on your intended area. It will probably be good to try shooting multiple times, each with a slightly different point of focus. Also familiarize yourself with different ways of achieving accurate focus, such as AF point expansion in Live View shooting or ways to micro-adjust focus through manual focusing (MF).
For more on depth-of-field, click below:
Camera Basics #1: Aperture
EOS 5D Mark III/ EF50mm f/1.4 USM/ FL: 50mm/ Aperture-priority AE (f/1.4, 1/50 sec, EV±0)/ ISO 100/ WB: Auto
When you close in on a subject that is small in size, the depth-of-field becomes extremely shallow, and your focus will also have to be pin-point precise. MF might be a very effective option depending on the scene.
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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.
Published by Impress Corporation
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.