What is a film gate and how does this affect my negative?

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Konvas 2M
Konvas 2M (no lens)

In a motion picture camera, the size of the film gate will determine the size of the individual frame exposed. A film gate can be seen when you remove the lens and look into the camera body. You may need to rotate the mirror shutter a little to get a clear view, but right there will be the gate. If you have loaded some film into the camera, then you will see a small "window" of the brown negative. The surrounding edge of the window, usually made of metal, is the film gate. It is a rectangular opening that allows a small section of film to be exposed to light (once exposed, it will be called a "frame") when that section passes thru the gate. When shooting with 35mm, if the size of the gate is 18.7mm x 24.9mm (also known as "Super-35"), then the size of the negative's frame that will be exposed will also be 18.7mm x 24.9mm.

There are many different gate sizes, but the most standard for origination with cinematic 35mm cameras are Wide-screen Anamorphic : 18.7mm x 22mm, Super-35 (also called Silent 35 or Full Aperture): 18.7mm x 24.9mm, and Academy (or Standard 35mm): 16mm x 22mm.

In the world of 16mm, there is Standard 16mm (Double-Perf, Regular 16, or just 16mm): 7.5mm x 10.4mm, and Super 16: 7.5mm x 12.4mm. Sometimes you will hear of a very rare 16mm format that most labs/telecine houses don't support, called Ultra 16: 6.23mm x 11.8mm.

In the world of Super-8-mm, the gate is much smaller: 4.01mm x 5.46mm. Regular 8mm, although it uses the same 8mm wide negative as Super-8-mm, was designed differently and the gate is even smaller still: 3.3mm x 4.5mm.

Konvas Gate
Konvas Gate

You can modify a camera's gate to cover more of the negative from exposure. This is often called "Masking", and covers the frame to a desired ratio (this is often done for tighter control by the director: because the film could, theoretically, be played 'full frame', against the director's wishes, revealing things he or she didn't want to be shown). A 35mm Academy frame is 1.37:1 ratio, but the frame can be masked to 1.66:1, 1.78:1, or 1.85:1 ratios. It is usually considered a better idea to shoot in Academy frame, without a mask, to allow a slightly wider tolerance for mistakes.

Using 35mm cinema cameras, there are two different 3-perf gates: one is called "3-perf " or sometimes "3-perf Standard", which is basically 3/4 the height of a Standard 35mm frame and the same width as Standard 35mm: 13.9mm x 22mm. The new ratio is 1.56:1 and a 1.85:1 image can be cropped from that with no difference in image quality compared to "Standard 35 (4-perf)". The other 3-perf gate is "3-perf Super35 " which uses a wider gate. It's ratio is 1.76:1 and a 1.85:1 widescreen can easily be cropped from it. If a 1.85:1 frame is cropped from 3-perf Super35, then the area of the negative exposed from the gate is actually larger than the area of a standard 35mm frame when it has been cropped to 1.85:1 and projected. 3-perf Super35 is often used for transferring to anamorphic widescreen, due to its larger negative and its ability to save film.

Lastly, there's the "2-perf" or "Techniscope" gate for 35mm cinema film. The ratio of a 2-perf gate is natively 2.35:1, which is the same ratio as the projected image of anamorphic widescreen. Techniscope is almost half the height of 4-perf widescreen, and the same width: 9.47mm x 22mm. Techniscope is often used when transferring to anamorphic widescreen, due to it's native 2.35:1 ratio. It is also often used in place of Super16, since the frame area is 2.2 times larger (super16 is 2mm shorter and 11.6mm narrower), 2-perf is considered by some to be less expensive to shoot than super16.

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