Lens Focal Length: What to Use When
A sometimes overlooked, but major factor of composition is your choice of lens focal length. DSLRs and pro video cameras have removable lenses and can accept prime (fixed focal length) lenses, while other video cameras have a zoom lens permanently affixed to the camera. To adjust focal length on any zoom lens you simply zoom in or out to wide, normal, or telephoto lengths. In the footage below, the model stood in the same spot while I adjusted a fixed zoom lens, then moved the camera forward or backward to maintain the same subject framing.
Zoom Technique: Zoom lens to midpoint
Prime Lens Equivalent: 50 mm
- Both foreground and background remain in focus
- Most resembles the eye’s natural perspective
Zoom Technique: Zoom fully in
Prime Lens Equivalent: 70 mm
- Background soft-focused
- Much less of the background is visible
- Distant objects appear closer and more compressed
Zoom Technique: Zoom fully out
Prime Lens Equivalent: 14 mm
- Objects close to lens are distorted
- Distance greatly exaggerated
- Much more background is visible
- Background objects shrink in size
Which Focal Length to Use for Which Shot?
There’s no straight answer to this question, because it partly depends on your particular shooting situation as well as what you wanna show and how you want to show it. Want to show that a downtown street is really crowded? Break out the telephoto lens and compress that mass of humanity for the audience. Need to cover a convo of two subjects in the front seat of a moving car? Better have a wide angle lens in your kit. Gotta cover a short one-time-only event? No time to be switching up lenses during a firefight! Use a zoom lens to get full coverage with close-ups, mediums, and wide shots in three minutes flat.
If you know you’ll be shooting in tight quarters like cars, small rooms, or just a packed crowd, a wide lens is a must.
Excerpt from The Shut Up and Shoot Documentary Guide: A Down & Dirty DV Production, 2nd Edition by Anthony Q. Artis © 2014 Taylor and Francis Group. All Rights Reserved.