Film formats

Simulator

What the drawings show

• The gauge

  The gauge is the width of the film: 8, 16, 35 or 65 mm. It says nothing on its own about the frame, which depends on how many perforations the camera pulls down for each picture, whether a sound track takes a share of the width, and whether the film runs vertically or sideways through the gate.

• Perforations and pitch

  The holes along the edge are what the camera's claw pulls on, one tooth at a time. The pitch is the distance from one hole to the next: 4.75 mm on 35 and 65 mm, 7.62 mm on 16 mm, 3.81 mm on Standard 8, 4.23 mm on Super 8. The frame pitch is that figure times the holes per frame, and it fixes how much film a second of picture uses.

• The frame line

  The thin dark bar between frames is unexposed film. On 16 mm and Standard 8 the perforation sits on the frame line; on 35 mm the line falls between two perforations, and on Super 8 the hole sits beside the middle of the frame. The gap is a few tenths of a millimetre, so a projector's gate can hide it.

• Camera aperture, projected picture

  The frames drawn here are camera apertures, the opening in the gate the camera exposes. A projector's aperture is a little smaller, so the edge of the frame is never seen, and a widescreen release crops more: the 1.85:1 picture on the Academy strip is dashed because the film records the whole Academy frame and the cinema shows the middle.

• Sound on the film

  A grey band beside the picture is the optical sound track, a photograph of the sound wave that a lamp and a cell read in the projector. It took its share of the 35 mm width from 1929, which is why the Academy and anamorphic frames sit to one side. Camera negatives have no track; it is printed onto the release print.

• Film that runs sideways

  VistaVision and IMAX turn the film ninety degrees. The width of the film becomes the height of the frame, and the frame's width is set by the number of perforations instead: eight on VistaVision, fifteen on IMAX. The same stock gives a far larger frame at the cost of moving the film much faster.

• What the frame's area buys

  A larger frame holds more grains, so the picture is finer and sharper for the same stock, and a longer lens is needed for the same view, which gives a shallower depth of field at the same stop. The same is true of a digital sensor, which is why the cards give each sensor's area as a share of the frame.

• The digital cards

  Each card is a sensor near the frame in size, drawn against it in blue over rust. The percentage is the sensor's area against the frame's: a sensor at 95 percent frames almost as the film did with the same lens, one at 40 percent needs a lens about half as long. Clicking a card lays the sensor on the strip's frame.

• Where the figures come from

  The frame sizes are the camera apertures Sensor sizes uses. Perforation sizes, pitches and edge distances are the nominal figures of the film standards, rounded to the nearest hundredth. The margins between the perforations and the picture follow from those figures, so they may be a few tenths of a millimetre off a particular camera's gate. Sensor sizes are the makers' active areas in the modes named.