Focal Length, Aperture & What to Buy First
Everything you need to know about camera lenses in plain English. No jargon, no confusion, just clear answers and the right lens for your camera.
When you buy a camera, the body is just the beginning. The lens is what actually forms the image it determines how wide or tight your shot is, how blurry the background becomes, and how well the camera performs in low light. Understanding lenses is the single most important step in improving your photography, and it is far simpler than most guides make it seem.
This guide explains the two numbers that matter most focal length and aperture in plain English. It then covers the prime vs zoom debate and helps you decide which lens to buy first. We finish with four lenses available at Carlos.gi, covering Canon, Nikon, and Fujifilm systems from £284.
Focal Length: How Wide or Tight Is Your Shot?
Focal length is measured in millimetres (mm) and tells you how much of the scene your lens can see. A low number means a wide view great for landscapes and interiors. A high number means a narrow, magnified view great for wildlife and sports. A number in the middle (around 35–85mm) looks similar to what the human eye sees naturally, which is why these are called "standard" lenses and are ideal for portraits and everyday photography.
Aperture: Background Blur & Low Light Performance
Aperture is the opening inside the lens that lets light in. It is written as an f-number (f/1.8, f/2.8, f/4, etc.). Here is the counterintuitive part: a smaller f-number means a larger opening. So f/1.8 lets in far more light than f/4. This matters for two things: how blurry the background gets (called "bokeh"), and how well the lens performs in dim conditions.
| Aperture | Background Blur | Low Light | Typical Use |
|---|---|---|---|
| f/1.4–f/1.8 | Very strong | Excellent | Portraits, indoor, events |
| f/2–f/2.8 | Strong | Very good | Street, travel, portraits |
| f/4 | Moderate | Good | Landscape, zoom lenses |
| f/5.6–f/6.3 | Minimal | Limited | Kit lenses, bright conditions |
Prime vs Zoom: Which Should You Buy?
A prime lens has a fixed focal length (e.g. 50mm) you cannot zoom in or out. A zoom lens covers a range (e.g. 24–105mm) you can adjust how wide or tight your shot is. Both have real advantages, and the right choice depends on how you shoot.
What to Buy First
All 4 Lenses Compared
| Lens | Type | Aperture | Price | Score |
|---|---|---|---|---|
| Canon RF 50mm f/1.8 STM | Prime · Canon RF | f/1.8 | £209 | 94% |
| Nikon Z 40mm f/2 | Prime · Nikon Z | f/2 | £219 | 92% |
| Nikon NIKKOR Z 24-50mm f/4-6.3 | Zoom · Nikon Z | f/4-6.3 | £349 | 87% |
| Fujifilm XF 16-50mm f/2.8-4.8 | Zoom · Fujifilm X | f/2.8-4.8 | £629 | 90% |
Canon RF 50mm f/1.8 STM Lens
Prime · Canon RF Mount · f/1.8 · STM Autofocus · 43mm Filter Thread
The Canon RF 50mm f/1.8 STM is the lens we recommend to every Canon mirrorless camera owner as their first prime. It is compact, lightweight, and produces images that are noticeably sharper and more flattering than the kit lens particularly for portraits and indoor photography. The f/1.8 aperture creates beautiful background blur and allows shooting in low light without raising ISO to noisy levels.
The STM autofocus motor is quiet and smooth ideal for video as well as stills. On a Canon APS-C camera (like the EOS R50 or R100), the 50mm focal length behaves like an 80mm portrait lens, which is a flattering focal length for close-up portraits. On a full-frame Canon (R6, R5), it behaves as a true 50mm standard lens. At £209 (reduced from £239), it is exceptional value for a lens of this quality.
Nikon Z 40mm f/2 Lens
Prime · Nikon Z Mount · f/2 · Ultra-Compact · 52mm Filter Thread
The Nikon Z 40mm f/2 is one of the most impressive lenses in Nikon's Z-mount lineup not because of its price, but because of how little it compromises. It is extraordinarily compact: at just 45.5mm long and 170g, it barely extends beyond the camera body. Yet it produces sharp, contrasty images with pleasing bokeh at f/2, and its autofocus is fast and reliable on all Nikon Z cameras.
On a Nikon Z APS-C camera (like the Z50 II or Zfc), the 40mm focal length becomes approximately 60mm a flattering portrait focal length. On a full-frame Nikon Z (Z6 III, Z8), it is a classic street and documentary focal length that many photographers consider the most natural-looking perspective. At £219 (reduced from £259), it is the best value prime lens for Nikon Z users and an ideal first upgrade from the kit lens.
Nikon NIKKOR Z 24-50mm f/4-6.3 Lens
Zoom · Nikon Z Mount · f/4-6.3 · Collapsible · Kit Lens Upgrade
The Nikon NIKKOR Z 24-50mm f/4-6.3 is the collapsible kit zoom that ships with several Nikon Z full-frame cameras. It covers the most useful focal length range for everyday photography from wide-angle (24mm) to a short telephoto (50mm) in a remarkably compact package that collapses flat when not in use. It is the lens to choose if you want versatility in a small form factor for travel and everyday shooting.
Image quality is solid throughout the zoom range, and autofocus is fast and reliable. The variable aperture (f/4 at 24mm, f/6.3 at 50mm) means it is not ideal for indoor or low-light shooting for that, the Z 40mm f/2 is a better choice. But for outdoor photography in good light, travel, and general use, the 24-50mm provides genuine versatility that a prime lens cannot match.
Fujifilm XF 16-50mm f/2.8-4.8 R LM WR Lens
Zoom · Fujifilm X Mount · f/2.8-4.8 · Weather Resistant · Linear Motor AF
The Fujifilm XF 16-50mm f/2.8-4.8 R LM WR is the most capable all-round zoom lens for Fujifilm X-mount cameras. It covers a wide-to-standard range (equivalent to 24-76mm on full frame) with a faster maximum aperture than most kit lenses f/2.8 at the wide end is genuinely useful for indoor and low-light shooting. The weather-resistant construction makes it suitable for shooting in rain and dusty conditions, which is a significant advantage over most lenses at this price.
The linear motor autofocus is fast, quiet, and accurate well-suited to both stills and video. Image quality is excellent throughout the zoom range, with minimal distortion and good sharpness even at the edges of the frame. At £853, it is a premium purchase, but for Fujifilm users who want one lens that handles most situations from landscapes to portraits to street photography this is the definitive choice.
Our Recommendations
"The best lens upgrade you can make is a fast prime. One lens with f/1.8 will transform your photography more than any camera body upgrade."
For Canon users, the Canon RF 50mm f/1.8 STM is the clear first choice exceptional image quality at an accessible price. Nikon Z users should start with the Nikon Z 40mm f/2 compact, sharp, and fast. If you need zoom versatility on Nikon Z, add the NIKKOR Z 24-50mm. Fujifilm users wanting one lens for everything should invest in the XF 16-50mm f/2.8-4.8 WR.
| Rank | Lens | Best For | Score |
|---|---|---|---|
| 1st | Canon RF 50mm f/1.8 STM | Canon users · portraits · low light | 94% |
| 2nd | Nikon Z 40mm f/2 | Nikon users · everyday · compact | 92% |
| 3rd | Fujifilm XF 16-50mm f/2.8-4.8 | Fujifilm users · travel · versatility | 90% |
| 4th | Nikon NIKKOR Z 24-50mm f/4-6.3 | Nikon users · outdoor · travel zoom | 87% |
256 lenses in stock Canon, Nikon, Fujifilm, Sony, Sigma and more. Free local delivery in Gibraltar.
