A chronogram is a strip of video frames sampled at equal time intervals and saved as one image. Where a kinogram shows hand-picked positions, a chronogram shows time itself: equal gaps in time, so unequal gaps in the picture reveal exactly where the movement speeds up, slows down, or hesitates.
Chronogram vs. kinogram
| Kinogram | Chronogram | |
|---|---|---|
| Frames chosen by | You — key positions | The app — equal time steps |
| Answers | "What do the positions look like?" | "How is the movement timed?" |
| Best for | Technique review, position checklists | Rhythm, tempo, acceleration, hesitation |
| Effort | A minute of frame-picking | Two taps |
The two are descendants of chronophotography — Muybridge's galloping horse and Marey's flying pelicans were chronograms before film existed. The equal spacing is the whole point: it makes time visible.
What to read in a chronogram
- Bunched frames = slow, spread frames = fast. In a sprint chronogram, the athlete should travel a growing, then constant distance between frames. A cluster mid-strip is a deceleration you'd never spot at full speed.
- Rhythm faults. A golf transition that rushes, a serve toss that hangs, a lifter who stalls at the knee — all show up as an uneven progression across the strip.
- Consistency between reps. Export a chronogram of the good rep and the bad rep with the same frame count and compare them frame column by frame column.
How to export a chronogram
- Load the video and trim the timeline to just the movement — drag the trim handles so the sampling window doesn't waste frames on walking up.
- Tap Save, then choose Chronogram.
- Pick the frame count (5–40; 30 is the default — fewer frames for a short explosive movement, more for a full sprint) and Horizontal or Vertical orientation.
- Export. The strip is saved to Photos as one image.
Any drawings you've made — reference lines, angles — are part of the picture, so you can add a horizontal line at hip height first and then read hip-height consistency across all 30 frames.
When to reach for which export
The app's Save menu offers four formats; a useful habit is:
- Video — the full review with sound and motion.
- GIF — a short loop for chats.
- Kinogram — positions, hand-picked. Technique discussion.
- Chronogram — timing, automatic. Rhythm discussion and quick progress records.
Export chronograms in Coach Video Analysis
Chronogram export is built into the Save menu: pick 5–40 evenly spaced frames, horizontal or vertical, one image to Photos. Pair it with the trim handles for a clean sampling window and with Markup reference lines to make the timing story obvious. Free to download on iPhone, iPad, and Mac.
