Exposure and Lens Choice: How Lens Speed Affects Your Photography
Understanding exposure is essential for choosing the right lens. Learn how maximum aperture affects shutter speed, ISO, and image quality across different shooting conditions.
Lens speed — the maximum aperture of a lens — is one of the most important factors in exposure. A faster lens (wider maximum aperture) lets in more light, allowing faster shutter speeds and lower ISO settings in any given lighting condition. This guide explains how lens speed affects exposure and how to choose the right aperture for your shooting needs.
How Lens Speed Affects Exposure
Each full stop of aperture doubles or halves the amount of light reaching the sensor. An f/1.4 lens lets in twice as much light as an f/2 lens, four times as much as an f/2.8 lens, and sixteen times as much as an f/5.6 lens. In practical terms, this means:
- An f/1.4 lens can shoot at 1/125s shutter speed indoors where an f/5.6 needs 1/8s — the difference between sharp and blurry handheld images
- An f/1.8 lens at ISO 1600 produces cleaner images than an f/4 lens at ISO 6400 in the same light
- f/2.8 zooms are the minimum recommended aperture for indoor event and wedding photography
- f/4 zooms work well for daytime and well-lit studio work but struggle in dim conditions
Choosing the Right Lens Speed
- f/1.2–1.4: Essential for professional low-light work (weddings, events, indoor sports). Significant price and weight premium.
- f/1.8: Excellent balance of speed, size, and cost. Best value for most photographers. Works well in moderate low light.
- f/2–2.8: Good for general photography. f/2.8 zooms are professional standards for events and portraiture.
- f/4: Adequate for well-lit conditions. Significantly lighter and cheaper than f/2.8 zooms. Good for travel and landscape.
- f/5.6: Typical for kit zooms and budget telephoto lenses. Requires good light or high ISO for acceptable results.
Low-Light Lens Recommendations by Budget
- Under $200: Canon EF 50mm f/1.8 STM ($99–$150 used) or Nikon 50mm f/1.8D ($80–$130 used) — fast and affordable
- $200–$500: Sony FE 50mm f/1.8 ($150–$250 used), Canon RF 50mm f/1.8 ($150–$200 used), or Sigma 30mm f/1.4 DC DN ($200–$300 used)
- $500–$1,000: Tamron 28-75mm f/2.8 Di III RXD ($400–$600 used) or Canon RF 85mm f/2 Macro IS STM ($400–$550 used)
- $1,000+: Sony FE 24-70mm f/2.8 GM II ($1,800–$2,400 used) or Canon RF 24-70mm f/2.8L IS USM ($1,800–$2,400 used)
