10 Concepts to Know Before Buying Your Second Lens
You’ve been shooting with your kit lens for a while, and you feel that you’re ready for something more. What kind of lenses are there and how are they different? We unravel the jargon and share some features you should pay attention to.
1. Focal length
Describes how much of the scene can be captured in the frame
The focal length of a lens tells us its angle of view, i.e., how much of the scene can be captured and how large subjects within the frame appear.
A shorter focal length provides a wider angle of view, whereas a longer focal length provides a narrower angle of view.
Know this: Lenses can be categorised based on their focal length
| Lens category | Focal length (35mm equivalent) |
| Ultra-wide angle | 24mm and below |
| Wide angle | 35mm and below |
| Standard | 40mm to <70mm |
| Medium telephoto | 70 to 135mm |
| Telephoto | >135mm |
| Super telephoto | 400mm and above |
Kit lenses usually offer a wide-angle to medium telephoto angle of view. For example, the RF-S18-45mm f/4.5-6.3 lens offers a full-frame-equivalent angle of view of 28.8mm to 72mm due to its 1.6x “crop factor”. (We’ll explain what this means in the next point.)
If you want to capture more of a scene than possible on your kit lens, look for an ultra-wide-angle lens.
If you want wildlife and other faraway objects to look bigger in the frame, look for a telephoto or super telephoto lens.
Learn more about how to use different focal ranges for artistic expression in:
Professional Composition Techniques (3): Making Good Use of Lenses
Different Lens, Different Expressions: Landscape & Nature Photography
Composition Techniques for Wide-Angle Lenses
2. “Crop factor”
The effective focal length on an APS-C camera
If you use an APS-C camera, remember to multiply the focal length in the lens name by 1.6x to get the effective angle of view in full-frame focal length terms. Otherwise, you might end up with a tighter angle of view than expected!
This is because the smaller APS-C image sensor records less of the scene, giving a “zoomed-in” effect. On Canon APS-C cameras, the “zoom-in” effect is 1.6x, so 50mm gives an angle of view that is equivalent to 80mm (50 x 1.6) on a full-frame camera.
Also, see:
4 RF Prime Lenses to Use with Your APS-C Camera
3. Maximum aperture
Impacts depth-of-field (bokeh) and low-light settings
The aperture refers to the opening in the lens that allows light to enter. It is made up of lens blades that move to change the size of the opening for exposure control. The largest possible opening is called the lens’ “maximum aperture”. This is measured in terms of f-stops (f-number). You can find the maximum aperture in the name of the lens, e.g., RF50mm f/1.8 STM. (In some lens names, this may be a range, e.g., f/4.5-6.3. We explain more in Point 5.)
A smaller f-number indicates a bigger aperture, which allows more light to enter the system within a given duration. This enables more flexibility with the shutter speed and ISO speed settings. It also suggests a shallower depth-of-field, which means more intense bokeh (out-of-focus blurring effect).
Bokeh
f/1.8
f/4
Low light
A lens with a larger maximum aperture enables more intense bokeh. It also lets you use a faster shutter speed to freeze fast movement when shooting in low light, or a lower ISO speed to ensure a cleaner image without visible grain.
f/1.8 @ 1/1000 sec
f/4 @ 1/200 sec
Both images were shot at ISO 12800. The faster shutter speed enabled by f/1.8 allowed us to freeze the leftmost ball in midair with no motion blur.
Know this: A larger maximum aperture also enhances AF performance.
Also, see:
Lens FAQ #2: Can A Fast Lens Really Make It Easier To See Through The Viewfinder?
Lens FAQ #9: What is the difference between an f/2.8 and an f/4 telephoto zoom lens?
4. Prime and zoom lenses
Convenience & unexplored focal ranges: Zoom lens
Bokeh and portability: Prime lens
There are two main categories of lenses available: prime lenses and zoom lenses.
Most kit lenses are zoom lenses: you can change the focal length (zoom in and out) by turning the zoom ring. If you’re buying a new lens to use an angle of view that your kit lens doesn’t provide, a zoom lens provides the most convenience!
Prime lenses have only one focal length, so you must “zoom with your feet”. But because they have simpler structures, it’s easier to incorporate a larger maximum aperture while keeping them compact and lightweight. If you want better bokeh or low-light performance, but also need something small or are on a tight budget, consider a prime lens.
More details about both types of lenses in:
Prime Lens or Zoom Lens: Which Should I Buy?
EOS R100/ RF85mm f/2 Macro IS STM @ FL: 85mm (136mm equivalent), f/2, 1/800 sec, ISO 100
The beautiful foreground and background bokeh in this shot complement the soft, velvety texture of flower petals. It was created through the combination of a long focal length and a large f/2 maximum aperture.
Tip: Prime lenses are good for training composition as they force you to work harder to get a good shot. Use the same focal length for long enough, and you’ll have a good idea of what will fit into the frame even without checking the viewfinder! That’s how some street photographers get a decent shot even when shooting from the hip.
5. Variable and constant aperture zoom lenses
5. Variable and constant aperture zoom lenses
What kind of versatility do you need more?
Variable aperture zoom lenses
Most kit lenses are variable aperture zoom lenses. You can tell by the lens name, where the maximum aperture is stated as a range, e.g., RF-S18-45mm f/4.5-6.3 IS STM.
The maximum aperture changes with the focal length, and is usually the largest at the wide-angle end and the narrowest at the tele end. For example, with the RF24-105mm f/4-7.1 IS STM, you can set a maximum aperture of f/4 at 24mm, but this gradually decreases as you zoom in. At 105mm, the widest aperture you can set is f/7.1.
Variable aperture zoom lenses are usually smaller, lighter, and more affordable. They are a good choice if portability is very important to you, and you shoot mostly in the daytime under good lighting conditions.
Constant aperture lenses
Constant aperture zoom lenses have the same maximum aperture regardless of the focal length in use. For example, on the RF24-105mm f/4L IS USM, you can set the aperture at f/4 at any focal length from 24 to 105mm. This makes them more versatile than variable aperture lenses. These lenses are also usually professional lenses, which ensure better image quality and a more durable build with weather sealing.
6. Closest focusing distance and maximum magnification
6. Closest focusing distance and maximum magnification
Important for macro and close-up photography
The closest focusing distance (or minimum shooting distance) is a lens specification that suggests the shortest working distance possible before the lens becomes unable to focus.
Maximum magnification is a related concept. It suggests the size of the subject will appear in the frame at the closest focusing distance. It is also affected by the focal length.
You don’t necessarily always want the shortest closest focusing distance. Sensitive subjects such as insects may fly away if your lens is too close! That’s why telephoto macro lenses such as the RF100mm f/2.8L Macro IS USM are so popular for macro photography: they offer a high maximum magnification even when shooting a comfortable distance away.
7. Extender compatibility
Increasing the reach of your telephoto lens
An extender, also known as a teleconverter, increases the focal length of your lens when attached. The increase factor is in the extender’s name. For example, using the Extender RF2x with the RF100-400mm f/5.6-8 IS USM doubles the focal range to 200 to 800mm, which achieves better close-ups of birds and wildlife! They are a relatively portable and budget-friendly way to achieve greater reach when necessary.
Two things to note about extenders:
1. They are only compatible with certain lenses
If you think you need one, make sure you buy a compatible lens.
2. They decrease the maximum aperture
A 1.4x extender reduces the aperture by 1 f-stop, and a 2x extender by 2 f-stops.
| Maximum aperture | With Extender RF1.4x | With Extender RF2x |
| f/2.8 | f/4 | f/5.6 |
| f/4 | f/5.6 | f/8 |
| f/5.6 | f/8 | f/11 |
| f/8 | f/11 | f/16 |
| f/11 | f/16 | f/22 |
A lens with a larger maximum aperture will offer more flexibility with an extender. More light entering the lens also helps autofocus performance!
8. The difference between RF and RF-S lenses
Lenses designed for full-frame cameras vs. APS-C cameras
There are two kinds of RF mount lenses. While both can be used on any EOS R system camera without a mount adapter, there are key differences:
|
|
|
|
| Designed for |
|
|
| Form factor | Usually larger (must cater to the larger full-frame image sensor) |
Smaller and lighter (APS-C image sensors are smaller) |
| When attached to a full-frame camera |
|
|
| When attached to an APS-C camera |
|
|
Learn more in:
Full-Frame vs APS-C Camera: Which Should I Choose?
9. The difference between EF and RF lenses
What’s the difference between old and new?
EF/EF-S lenses use an older mount system designed for EOS DSLR cameras. RF/RF-S lenses are the newer mount system designed for the EOS R mirrorless camera system and are more technologically advanced.
RF/RF-S lenses cannot be used on EOS DSLRs or EOS M-series mirrorless cameras. You will need a mount adapter to use EF/EF-S lenses with an EOS R-series camera.
Our article on EF vs RF lenses offers more in-depth information on the differences between the two systems. But essentially, RF/RF-S lenses provide the best performance and functionality with EOS R series cameras.
Know this: The improved lens-camera communication on RF/RF-S lenses enables new features. One example is this real-time focus distance display scale in the Live View/EVF display (shown above), which helps with manual focusing.
10. L-series lenses
Weather sealing and the best possible image quality
“L” series lenses have the letter “L” in the lens name and a red line around the barrel. They indicate a professional-grade lens. Such lenses have:
- An optical design that ensures the clearest, sharpest image quality
- Mechanics for fast, seamless autofocus performance
- Dust- and drip resistance to ensure durability and reliability in various weather conditions.
If you often shoot outdoors, especially in damp or dusty places such as forests and waterfalls, the weather-sealing and durability of an L-series lens would be a worthwhile investment.
Know this: If you own an eligible EOS R series camera body and at least 3 L-series lenses, you qualify for free EOS Professional Silver Membership, which gives you benefits. For more details, see Canon Professional Services (Asia). Keep this in mind as you build your lens collection!
