Focal length
Also known as: lens length, millimetres
The optical property that decides how wide a lens sees, quoted in millimetres and the single biggest influence on how a shot feels.
Updated
What it means
Focal length determines angle of view. A short length sees a wide scene and a long one sees a narrow slice, and the number alone tells somebody almost everything about the character of a shot.
It also changes apparent depth. A wide lens pushes the background away and exaggerates whatever is near the camera, where a long lens compresses the distance between foreground and background.
The quoted number means nothing without the sensor. A Crop factor translates between formats, which is why an action camera lens of a few millimetres sees roughly what a much longer lens would on a larger body.
How it works in practice
Action cameras are wide and fixed, which decides most things. A Wide lens of that kind makes a mount feel immediate and close, and it is the reason mounted footage looks the way it does.
Distance is the only control when the lens cannot change. Moving the camera closer is the equivalent of zooming in, except that the perspective changes with it rather than staying put.
A longer lens is what makes a trick look big. Compression flattens the gap between the rider and the landing, which is why filmers shoot jumps from far away rather than from beside them.
What to watch out for
Wide lenses make everything look smaller. A jump filmed on a mounted camera reads as half its real size, which is the single most common disappointment when reviewing a card.
They also distort near the edges. Fisheye distortion bends straight lines and stretches anything at the corner of frame, and correcting it crops into the picture.
Digital zoom is not a longer lens. Cropping into a frame narrows the view and keeps the wide perspective, so a Digital zoom shot looks like a wide shot that has lost some resolution.
How RawClip handles it
Clips from wide mounted cameras and from longer lenses are analysed together, and the difference in how big the action reads is part of what scoring weighs. Filming at least some of a session from a distance is what gives a sequence a sense of scale.