Understanding Digital SLR Lens Types and Focal Lengths - dummies

Understanding Digital SLR Lens Types and Focal Lengths

By Robert Correll

Part of Digital SLR Photography All-in-One For Dummies Cheat Sheet

Lenses are an important part of digital SLR photography. Knowing what types of lenses there are and what they do will help you choose the right lenses for the type of photography you want to pursue.

The general lens categories are:

  • Zoom lenses: Lenses that have a zoom ring that enables you to change the focal length are called zoom lenses. They come in several types. The most common, and in many ways, versatile type is called the Standard (or Normal) Zoom lens. There are also wide-angle and telephoto zoom lenses.

  • Prime lenses: A prime lens has a fixed focal length. A lens with a fixed focal length cannot zoom in or out. They are specialized lenses that do what they do well. Buy the lens that matches the focal length you like the best. When you compose your shots, you have to physically move closer or further away to zoom in and out.

  • Macro lenses: Macro lenses specialize in taking photos of close objects with a reproduction ratio close to 1:1. Most macro lenses are primes.

  • Other specialty lenses: This includes creative and artistic lenses such as:

    • Lensbaby: Nontraditional but creative. There are several different types of lenses that have different creative focus and depth of field effects.

    • Holga: A plastic Holga lens that is compatible with your dSLR and can be mounted directly. Awesome!

    • Diana+: Similar to Holga lenses, but have much more zoom in them. Requires an adapter.

    • Tilt-shift: Tilt-shift lenses tilt and shift, producing interesting depth of field and perspective effects.

    • Pinhole: Simply a pinhole that lets light into the camera. There is no focus. The aperture is so small the depth of field is huge. Expect longer exposure time. Pinhole cameras create soft dreamy photos.

Lenses are also categorized based on their focal lengths:

  • Ultra-wide angle: Ultra-wide angle lenses have a very wide angle of view. Their focal lengths are 20mm and below for full-frame cameras, 15mm and below for APS-C, and 10mm and below for Three Fourths dSLRs.

  • Wide-angle: Wide-angle focal lengths include from approximately 20-40mm for full-frame, 15-25mm for APS-C, and 10-20mm for Three Fourths cameras.

  • Normal: Normal focal lengths are around the same diagonal size as your camera’s sensor, give or take a small range. This includes 40-60mm for full-frame, 25-40mm for APS-C, and 20-30mm for Three Fourths cameras.

  • Near (also known as medium) telephoto: Near telephoto focal lengths run from approximately 60-200mm for full-frame cameras, 40-135mm for APS-C, and 30-100mm for Three Fourths system cameras.

  • Telephoto: This range is considered “proper telephoto.” It extends from the end of near telephoto and stops before things get ridiculously expensive. Typical telephoto focal lengths are from 200-300mm for full-frame, 135-200mm for APS-C, and 100-150mm for Three Fourths cameras.

  • Super telephoto: These lenses are singularly optimized to shoot incredible shots with ridiculous focal lengths. They run from 300mm and up on full-frame cameras, 200mm and over for APS-C, and 150mm and up for Three Fourths cameras.