Start a slow motion shot with the delivery frame rate and the amount of time you want to give an action. To stretch one second into four seconds in a 25p film, consider capturing 100 frames per second and playing those frames at 25fps. Then choose the shutter for the capture rate and check lighting and sound. Selecting a high frame rate alone does not determine the finished result.
A falling drop, moving fabric or a brief expression may contain detail worth extending. Identify that detail before selecting the frame rate. Slowing an entire demonstration can make an otherwise clear sequence feel unnecessarily long.
Calculate the slowdown from capture and playback rates
If every captured frame is retained, played once and given no further speed change, slowdown factor = capture frame rate ÷ playback frame rate. Speed relative to the real action is the inverse: playback rate ÷ capture rate. Capturing at 100fps and playing at 25fps gives a factor of four, or 25% of real time speed.
| Capture → playback (fps) | Relative speed | 2 seconds becomes |
|---|---|---|
| 50 → 25 | 50% | 4 seconds |
| 100 → 25 | 25% | 8 seconds |
| 60 → 30 | 50% | 4 seconds |
| 120 → 30 | 25% | 8 seconds |
These are calculations for integer frame rates, not a camera specification table. Sony’s α7 III S&Q guide separates the capture and recorded file rates and lists their playback relationships. For a project using rates such as 59.94 or 29.97, calculate with the actual values.
The editor also needs to decide how the footage plays. In Premiere, Adobe’s frame rate guide describes Modify → Interpret Footage → Assume this frame rate. This changes interpretation throughout the project, affecting duration and audio. Use Speed/Duration on a timeline instance when only that use of the clip needs a change.
Choose shutter from capture rate, then check the recorded image
A 180° shutter angle is a useful starting point for motion blur: exposure time is approximately 1 ÷ (2 × capture frame rate) seconds. At 100fps that is about 1/200 second. A 25p delivery does not make 1/50 second the corresponding setting for that capture rate. Sony’s Video 201 course explains the common relationship and how faster or slower shutters change the feel of movement.
Treat those numbers as a comparison, not a setting for every shot. With aperture, ISO and lighting unchanged, 1/200 second provides one quarter of the exposure time of 1/50 second. More light, a wider aperture and higher ISO involve different tradeoffs. If you open the aperture, recheck whether the moving product detail stays sufficiently clear; see the guide to depth of field for people and products.
A 180° setting does not establish that lights or screens will be free of flicker. Record the whole action at the intended frame rate, shutter and light output. Check brightness changes and horizontal bands before comparing changes to shutter or lighting. Sony’s high frequency flicker guide stresses checking the recorded image because it can differ from the monitor preview. Availability of fine shutter adjustment depends on the camera.
Check whether the file is already slowed and whether it has audio
Ordinary recording at a high frame rate and an in-camera mode such as S&Q can produce different files. The first can retain footage that plays at real time speed; the second may already create a slowed file at the selected playback rate. Check the mode, file frame rate, duration and audio before applying another slowdown.
Consult the specific camera documentation. For example, the linked Sony α7 III S&Q guide says that its S&Q mode records no sound and creates XAVC S HD files. Those restrictions do not describe every camera. If dialogue or the actual action sound is needed, confirm the recording method before the shoot and plan separate sound recording or material captured at normal speed.
Footage recorded at 25p can also be slowed in an edit, but the missing time samples need treatment. Adobe’s interpolation guide distinguishes repeating or removing existing frames, blending adjacent frames, and Optical Flow analysis that generates intermediate frames. Generated frames are not additional records captured on set. For product detail, inspect outlines, occlusions and moments of contact frame by frame.
Use a short test to settle the shot and handoff
Imagine a fictional 25p product film that gives four seconds to a drop falling into a cup over one second. Capture at 100fps is a starting point to compare, and about 1/200 second is the exposure calculation for a 180° shutter. This is an illustrative setup, not a client case or an equipment test.
- Define the shot’s purpose. Is the important detail the drop’s shape, its contact with the rim or the cup’s construction? Give that event a clear angle and enough space in the frame.
- Confirm delivery and recording mode. Note capture rate, delivery rate, format and any in-camera slowdown. Check the mode’s resolution, crop, focus and audio restrictions.
- Record the whole action. Use the actual lighting and leave room before and after the event. Review exposure, flicker, motion blur and focus. Change one main factor for the next comparison.
- Play it at the delivery rate. Confirm that the one-second event becomes four seconds as intended, without a second slowdown. If interpolation is used, inspect the product’s shape in generated frames.
- Hand over the actual settings. Supply original files with the mode, capture and playback rates, retiming method and sound plan. Retain originals before further speed changes.
If the shot explains performance or elapsed time, also retain a normal speed reference and identify the slowdown in its presentation. Screen duration must be distinguishable from the action’s actual duration. The product test filming and review guide explains how to preserve conditions and process records.
Choose a slow motion frame rate by calculating the required time expansion, then confirming that the setting produces usable clarity, exposure and an explicit sound plan. A short recorded test makes the decision more concrete than selecting the camera’s highest available rate.
Sources and review date
The topic came from filmmaking study notes and was independently developed for this article. Frame rate, recording mode, shutter and editing details were checked against the linked Sony and Adobe documentation on 2 October 2026. The table contains mathematical examples. The workflow and fictional drop setup are editorial suggestions, not equipment tests or universal specifications.