Anamorphic lenses explained

An anamorphic lens squeezes a wide view sideways onto the sensor, and the picture is stretched back out in post. The squeeze is why those lenses frame wider than their focal length suggests, why they pair with near-square recording modes, and why their out-of-focus highlights turn into ovals. This guide does the arithmetic with real modes and one worked example.

Squeeze and desqueeze

A lens with a squeeze of S records S times more width than a spherical lens of the same focal length would on the same sensor. The picture on the sensor looks thin and tall. In the edit (or in the camera's monitor output) it is stretched by S horizontally, the desqueeze, and everything looks normal again.

For framing, the rule is simple: along the squeezed axis, treat the sensor as S times wider. A 2x lens on a mode 20.22 mm wide frames as if the mode were 40.44 mm wide. The vertical is untouched. So a 2x 50 mm has the horizontal angle of a 25 mm on the same sensor, with the vertical angle of a 50.

Why 6:5 and 4:3 modes exist

Multiply a mode's aspect by the squeeze and you get the shape of the desqueezed picture. A 6:5 mode is 1.2 wide for every 1 high; with a 2x squeeze that is 2.4, a hair wider than 2.39. A 4:3 mode with a 2x squeeze is about 2.67, so the sides are cropped for 2.39. Lighter squeezes go the other way: a 1.33x squeeze on a 16:9 mode lands close to 2.39 with almost nothing cut.

That is why makers offer anamorphic modes, and why the gear data flags 194 recording modes as made for anamorphic, like the 6:5 and 4:3 ones below. Here is what each combination needs to reach a 2.39 delivery:

"Kept" is the share of the mode's area inside the 2.39 frame. A delivery aspect is cut from the middle of the mode, as the app does it: 2.39 ÷ squeeze, in sensor terms. Figures computed from the recording mode sizes in Cutvey Viewfinder's gear data, counted November 2, 2026, with the app's own rules.

Two things stand out. A 2x lens on a 6:5 mode keeps almost the whole sensor, which is the reason the format exists. And a 4:3 mode with a 2x lens throws away a good slice of each side, which some DPs accept for the extra protection and others avoid.

A worked example

The scene is a two-shot in a living room on an ARRI ALEXA 35 in 3.3K 6:5, with a 50 mm from the Cooke Anamorphic/i S35 T2.3 (2x) series, delivering 2.39.

1. The mode. 20.22 mm × 16.95 mm, an aspect of 1.19.
2. The crop for 2.39. In sensor terms the frame is 2.39 ÷ 2 = 1.195 wide for every 1 high. The mode is a touch narrower than that, so the full width is kept and the height trimmed to 16.92 mm.
3. The horizontal angle. 2 × arctan(2 × 20.22 ÷ (2 × 50)) = 44.0°.
4. The vertical angle. 2 × arctan(16.92 ÷ 100) = 19.2°.
5. The spherical comparison. A spherical lens covering 44.0° on the same camera in 4K 16:9 (24.88 mm wide) would be a 30.8 mm. On the 6:5 mode itself it would be a 25 mm.

So the 2x 50 frames the room about as wide as a 31 mm would in the camera's ordinary 16:9 mode, and it keeps a 50 mm's depth of field.

Depth of field does not shrink with the frame

That last point is where anamorphic gets its reputation for shallow focus. You frame like a wide lens and focus like a long one. At T2.8 and 3 m, with the S35 circle of confusion of 0.025 mm the app picks for this mode's size, the 50 mm holds focus from 2.77 m to 3.27 m. A spherical 25 mm framing the same width from the same spot would hold from 2.25 m to 4.50 m.

Thin-lens figures, the exact forms the app uses. Distances from the lens's front principal plane; the marked T-stop is used as the stop, which reads slightly deep.

Cutvey Viewfinder's depth of field panel works the same way: it uses the marked focal length and stop, and does not account for the squeeze. The panel says so on screen. If you want to allow for the squeeze when judging how soft the background will look, do it by hand; the figures above are the unadjusted ones, which is what the panel shows. How depth of field is worked out explains the rest.

What the app knows about anamorphic

• The lenses. 108 anamorphic lens series in the gear data, with squeezes of 1.3x, 1.33x, 1.5x, 1.6x, 1.65x, 1.8x and 2.0x. A custom series takes any squeeze from 1.0 to 2.05, for rehoused or unusual glass.
• The modes. 194 recording modes are flagged as made for anamorphic, so a 6:5 or 4:3 mode is easy to find.
• The desqueeze. Pick the series and the frame is desqueezed on screen with the series' squeeze. A mixed kit uses each lens's own.
• Frame lines. Choose the delivery aspect, 2.39 for example, and add a second frame line inside it if you want to see a protection or a second delivery.
• Vertical. On a camera turned on its side, the squeeze moves to the vertical axis with it.

Anamorphic lenses and desqueeze shows the setup step by step. The anamorphic calculator works out the desqueezed aspect and the crop for any mode and squeeze in your browser.

A short checklist for an anamorphic job

• Pick the mode for the squeeze: near 6:5 for 2x, near 16:9 for 1.3x and 1.33x.
• Decide the delivery aspect before the scout, and frame to it.
• Check that the monitor or EVF is set to desqueeze, or the operator will be framing a thin picture.
• Expect a longer minimum focus from many anamorphic lenses than from spherical ones; check it on the rental sheet before you plan a close insert.
• Plan the focus marks with the real focal length, not the framing equivalent.

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