Lesson 6 of 12 · Module 2: Lenses and Focus
Focal Length and Lens Choice
Shoot two 8 second clips of the same subject at the same frame size, one at your kit lens’s widest focal length and one at its longest, repositioning your camera distance between the two so the subject fills the frame identically both times.
Cinematographer Explains 3 Different Camera Lenses
a working cinematographer physically repositions the camera between wide and telephoto lenses on the same subject, showing compression directly, exactly the walk-back drill in the lesson. Uploaded 2019.
Lens Compression Doesn’t Exist, Here’s Why
reputable photography education channel, real side-by-side across a wide range of focal lengths (15mm–1000mm) isolating distance vs. focal length as the actual cause of compression. Uploaded 2018.
Objective
Why This Matters
A zoom lens isn’t just a way to get closer without walking, it’s a way to change how the background relates to your subject. Two shots that frame a person identically at two different focal lengths and two different distances can look like they were shot in two different rooms. This is called compression, and it’s invisible until you deliberately isolate it, which is what this drill does.
The Technique
Set your kit lens to its widest focal length (often 16mm or 18mm depending on your specific lens). Position your subject with a background at least 10 feet behind them, more if you can manage it, something with visible scale reference (a doorway, a row of chairs, a person) helps show the compression effect. Get close enough that the subject fills a comfortable portion of the frame. Record 8 seconds.
Now zoom the kit lens to its longest focal length (often 50mm or 45mm depending on your specific lens). To keep the subject the same size in frame, you have to physically move backward, sometimes a significant distance, since a longer focal length magnifies everything including the walking-back you just did. Reframe until the subject occupies roughly the same amount of frame as the wide shot. Record another 8 seconds.
Compare on playback. At the wide end, the background should look smaller and farther, with generous context visible around your subject. At the telephoto end, that same background should look larger, closer, and squeezed up right behind your subject, even though nothing in the room actually moved. That apparent squeeze is compression, and it comes entirely from focal length and shooting distance, not from anything you did to the subject or the room.
If the two clips look nearly identical, you probably didn’t move back far enough for the telephoto shot, or your background wasn’t far enough behind the subject to register the difference.
Watch For This
Good
- Wide shot: subject matched in size to the telephoto shot, background visibly smaller and farther, more context in frame.
- Telephoto shot: subject matched in size to the wide shot, background visibly larger and closer, less context but stronger compression.
- The comparison is clean because subject framing size was actually matched, not just eyeballed loosely.
Classic Failure
- Subject size doesn’t match between the two clips because the camera wasn’t repositioned enough, making it an unfair comparison.
- Background was too close to the subject to show meaningful compression difference.
- The zoom was changed but the photographer never actually walked, defeating the entire point of the drill.
Your Drill
Position a subject with a background at least 10 feet behind them. Shoot one 8 second clip at your kit lens’s widest focal length, then reposition and shoot one 8 second clip at its longest focal length, matching subject frame size both times. 2 takes each, submit your best pair.
Shot it? The AI coach below reviews your clip against this lesson's pass checklist.
Pass Checklist
Lesson complete
Criterion met: At the wide end, the background appears smaller, farther away, and more of it is visible in frame; at the telephoto end, the same background appears larger, closer-looking, and more compressed behind the subject, while the subject’s size and framing match closely between the two clips.
Next: Lesson 7: Manual Focus and Focus PeakingHow solid did that feel?
Noted.
Coach Note
You zoomed to the long end but stayed in the same spot, so the subject blew up to twice the size instead of staying matched, and the comparison told us nothing about compression. Walk backward until the subject is the same size again, that walk is the whole lesson.
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Resurfaces In
Lesson 12 (Capstone).