How to use Canon lenses: prime lenses
11 Focus accurately
The wide maximum apertures offered by prime lenses enable you to work with a very shallow depth of field. This is a trait that you can exploit when shooting a portrait, allowing you to create a margarine-smooth background that doesn’t detract from the subject.
However, accurate focusing can be difficult when working at the very wide apertures of f/1.4 and f/1.8 typically offered by 50mm and 85mm lenses. If you want to make sure your model’s eyes are sharp, select One Shot AF and manually select a single AF point that’s positioned over their nearest eye.
12 Freeze action
Typically, primes are ‘fast’ lenses. This doesn’t mean they necessarily focus faster, but rather that they enable the use of faster shutter speeds thanks to their wider maximum apertures. For instance, the widest aperture you can select at 50mm on a Canon 18-55mm kit zoom is f/5.6.
However, the widest aperture available on Canon’s 50mm f/1.4 prime lens is four stops faster. That makes a massive difference to getting a blurred shot or sharp one; if an aperture of f/5.6 gives a shutter speed of 1/50 sec, then the f/1.4 aperture would give a shutter speed of 1/800 sec in the same situation.
13 Control the aperture
The choice of aperture has a big effect on the depth of field – or the amount of front-to-back sharpness there is in an image. Wider apertures (such as f/2.8) reduce the depth of field, while narrower apertures (such as f/22) increase it.
You’ll want precise control over the depth of field when you’re using a fast prime lenses, so set the camera in Aperture Priority (Av) mode.
Press your camera’s depth-of-field preview button as you change the aperture to see the effect it has on the image displayed in the viewfinder.
SEE MORE: DO or Di? Your lens markings explained
14 Fit a neutral density filter
Using the widest aperture on a fast prime lens can lead to overexposed pictures in bright conditions.
The reason for this is that the shutter speed required to make a normal exposure at this aperture may be faster than the camera’s fastest setting (such as 1/8000 sec on a 70D).
To get around this, you can fit a neutral density (ND) filter to the front of the lens to reduce the amount of light available, bringing the shutter speed back within the camera’s available range.
A variable ND filter can be a useful gadget if you shoot video, enabling you to adjust the strength of the effect as the light changes.
15 Zoom with your feet
Prime lenses offer a single focal length; they don’t zoom, so you’ll have to work harder to compose shots.
However, that also makes them excellent tools for learning the art of composition – if you’re new to photography, a cheap prime lens such as Canon’s 50mm f/1.8 makes an excellent investment.
The shallow depth of field offered by these lenses can be used as a compositional device too, allowing you to blur distractions and selectively focus to highlight a key feature of the scene.
What to consider when buying one of these Canon lenses…
16 Maximum aperture
Wider apertures let in more light, enabling faster shutter speeds and shallower depth of field – but they come with a price tag. Canon’s entry-level 50mm f/1.8 ‘nifty fifty’ costs around £90, while the f/1.4 version – at two-thirds of a stop faster – is almost £300. The top-end f/1.2 version costs over £1,200.
17 Filter thread
The front element and filter thread of a fast prime lens often has a large diameter, and this is something to bear in mind if you’ve already amassed a large collection of filters. You may need to upgrade them, and larger filters are more expensive.
18 Factor in sensor size
APS-C sensors are exposed to a smaller portion of the image projected by a lens. Multiply the lens focal length by 1.6 for the ‘effective’ focal length (EFL). This is good news for wildlife (a 400mm lens offers an EFL of 640mm) but bad news for landscapes (a 24mm lens offers an EFL of 39mm).
19 Aperture blades
Lenses with a more aperture blades usually produce better ‘bokeh’ (out-of-focus areas) because the lens opening is more rounded. This is why highlights captured with a Canon EF 50mm f/1.4 USM (8 blades) look smoother than those captured with the Canon EF 50mm f/1.8 II (5 blades).
20 Manual override
Look for a prime lens that offers full-time manual focusing, such as one fitted with Canon’s Ultrasonic motor (USM). This will enable you to fine-tune the focus point even when the camera’s using autofocus, which comes in very handy when you’re working with a particularly shallow depth of field.
PAGE 1 – How to use Canon lenses: standard & wide-angle zooms
PAGE 2 – How to use Canon lenses: prime lenses
PAGE 3 – How to use Canon lenses: telephotos & super zooms
PAGE 4 – How to use Canon lenses: specialist lenses
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