1 The idea
A pan turns the camera in place; a zoom changes the focal length in place. In both the camera doesn’t change position, so near and far things slide or grow together: no parallax. A dolly, orbit or crane moves the camera itself, so near things move faster than far ones: that’s parallax.
In VFX this is the first question for every shot. No parallax (a camera turning on a tripod) means a nodal/tripod solve or a 2D patch can work; with parallax, anything placed at depth usually needs a 3D camera track, though a flat surface (screen, wall, floor) can still be planar-tracked and a distant background or sky can often be 2D-tracked. Watch the numbers: in a zoom everything grows by the same amount; in a dolly the robot grows much faster than the poles.
2 Hands-on
Task: watch clips #A and #B and name the camera move in each
Compare “robot ×” with “poles ×” and the parallax angle. Explore mode shows every move with its name.
3 Deep dive
One question: did the camera change position?
Camera moves split into two groups: the camera stays put (pan, tilt, zoom, roll) or the camera travels (dolly, truck, orbit, crane, handheld). The first group has no parallax: the whole picture changes together. In the second, near and far separate.
| Move | Camera travels? | Parallax | Tell-tale |
|---|---|---|---|
| Pan / tilt | no | none | everything slides, angular sizes fixed |
| Zoom | no | none | everything grows equally |
| Dolly | yes, in/out | yes | near things grow much faster |
| Orbit | yes, around | strong | background sweeps the other way |
| Crane | yes, up/down | yes (vertical) | horizon shifts against the subject |
Measuring parallax as an angle
This room measures parallax as the angle between the direction to the robot and the direction to a pole behind it. If the camera only turns or zooms, that angle never changes (0°), because all directions turn together. If the camera travels, it changes straight away.
On-screen size is measured as angular size × focal. In the dolly the robot grows about 2.6× while the poles grow only about 1.4×; in the zoom both grow by the same ~2.7×.
The no-parallax point
A pan is truly parallax-free only when it turns about the lens’s centre of perspective (the entrance pupil, often called the nodal point). Ordinary tripod heads turn about the camera body, behind that point, so real pans show a little parallax, most visible when something is close to the lens.
For panoramas or tiled plates, crews use a nodal head that slides the camera so the pivot sits at the lens.
Something near the lens is what gives parallax away
Choosing a track from parallax
No parallax: a 2D track, planar track or nodal/tripod solve can work, and is faster and steadier. Parallax: anything placed at depth usually needs a full 3D (free-move) camera solve with tracks near and far, spread over the frame, though a flat surface can still be planar-tracked and a distant background or sky can often be 2D-tracked. Pick the wrong method and the first frame looks fine, then things slide as the camera moves.
- 1Watch near vs far
- 2Parallax or not?
- 3Nodal/2D or 3D solve
- 4Check with near and far cards
4 In real work
In Nuke
- Tracker: a pan/zoom shot without parallax can use a 2D track (translate, rotate, scale).
- CameraTracker (NukeX): dolly/orbit/crane shots need a 3D camera solve, with camera motion set to match the real move.
- Card + ScanlineRender: put cards near and far; if both stick to the plate through the shot, the solve holds.
- Project3D: in shots with parallax, project the plate onto simple geometry for clean plates or set extensions.
Common mistakes → the fix
- ✗ Using a 2D track on a dolly shot✓ Near and far move differently, so anything placed at depth needs a 3D camera (a 2D or planar track only holds for a flat surface or a very distant background).
- ✗ Reading a zoom as a dolly because the subject grows✓ Check whether the background grows as much as the subject; if it does, it’s a zoom.
- ✗ Solving a no-parallax shot as free move✓ Use a nodal/tripod solve, or the solver invents distances and focal.
Before you send the shot
- Know whether the shot has parallax before choosing a track
- Tracks near and far if solving in 3D
- Test cards don’t slide through the shot
- A zoom is tracked as a changing focal, not a changing distance
5 Check yourself
In a plate, the foreground and the background grow by exactly the same amount. Which move is it most likely?
🔒 Answer the question above and this card opens
1. In an orbit around the robot, its size barely changes but the background sweeps fast. Why?
2. A camera on an ordinary tripod pans slowly past a branch near the lens, and the branch shifts a little against the hills. Why?
Where the numbers come from: On-screen size is measured as angular size × focal length; parallax as the change in the angle between the robot and a pole 12 m behind it. Exact for a pinhole camera turning about its lens centre; real tripod heads rarely turn exactly about that point, so real pans can show a little parallax. The camera is an ideal pinhole (no lens distortion) with a 36 mm wide sensor cropped to 16:9 (36 × 20.25 mm). The set and robot are built in code with three.js.