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Aspect ratio refers to the width to height ratio of a movie image. For example, an aspect ratio of 2.39:1 means that the width is 2.39 times the height.
All movies are not the same size. Nearly all movies shown nowadays are either 1.85:1 or 2.39:1. Please read my movie formats document if you want to know why. Theatres should be built to handle both sizes, with movable masking at either the sides of the screen, or at the top and/or bottom of the screen.
Two theatres in Huntsville, the Regal Hollywood 18 and Regal Madison Square 12, which were originally built by Cobb Theatres, had many auditoriums with fixed-sized 1.85:1 screens not capable of handling scope (2.39:1) movies without 23 percent image loss on the sides. This problem is currently being corrected, beginning in November of 2002.
| Scope sized image (2.39:1). You'll always see the entire image at Huntsville's Carmike Cinemas 10, and at all Decatur, AL theatres. |
| The image, as was seen at Huntsville's Regal Hollywood 18 and Regal Madison Square 12 theatres in some of their thoughtlessly Cobb-designed 28' auditoriums that originally lacked movable masking. Approximately 22.6% of the image is lost on the sides when 2.39:1 movies are shown at 1.85:1. |
ANSI/SMPTE Standard 195-1993 specifies the following maximum dimensions for projector apertures:
| Format | Width | Height | Aspect Ratio |
| Flat Widescreen also called flat 2.5 perf |
0.825" (20.96mm) | 0.446" (11.33mm) | 1.85:1 |
| Scope (Cinemascope compatible) | 0.825" (20.96mm) | 0.690" (17.53mm) | 2.39:1 (with 2x unsqueeze) Often called 2.35:1 (was changed to 2.39:1 in 1971 to keep splices out of the projected image) |
These standard dimensions are shown in the following table:
| Flat 1.85:1 |
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For a correct presentation, the area within the red rectangle (projector aperture of 0.825" by 0.446") is projected onto a 1.85:1 sized screen. Examples: Good Will Hunting, Saving Private Ryan. |
| Scope 2.39:1 |
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For a correct presentation, the area within the red rectangle (projector aperture of 0.825" by 0.690") is projected with a 2x horizontal unsqueeze onto a 2.39:1 sized screen. Examples: Star Wars, October Sky. |
To quote the standard,
"In the absence of specific instructions to the contrary, it is intended that the actual projected film image area be the largest appropriately-shaped figure that can be inscribed within the specified dimensions."So, any theatre that crops scope movies to fit a 1.85:1 screen is probably using an aperture plate which allows an area approximately 0.639" wide (compared to the standard 0.825") and 0.690" high for their scope films, which covers up about 22.6 percent of the horizontal width of the images. This is not an "appropriately-shaped figure" for a "scope" movie. Compare the following diagram with the "Scope 2.39:1" diagram in the table above, remembering that the area within the red rectangle is projected with a 2x horizontal unsqueeze.
If a screen is of fixed size with no movable masking, 2.00:1 may, at first glance, seem to be a better aspect ratio than 1.85:1. The amount of image cropped from a scope film will be 16.3 instead of 22.6, but the amount of image cropped from a flat film will be 7.5 percent instead of zero percent! Assuming half the movies are scope, and half are flat, then the average loss of image is 15.1 percent with the 2.00:1 screen and 11.3 percent with a 1.85:1 screen. The 2.00:1 screen causes more image to be lost, on the average, even though it is between the two standard aspect ratios! Flat films look very tightly cropped and framed when played on 2.00:1 screens instead of 1.85:1 screens. No movies, except a few movies filmed in the Superscope process back in the 1950s, are shown properly on a non-adjustable 2.00:1 screen. There is no substitute for a screen that can be adjusted to both the 1.85:1 and 2.39:1 standard sizes.
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| A 1.85:1 flat image as it should be seen. |
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| The same image, when projected at 2.00:1. Note the loss of image at the top and bottom, although the image will be wider in the theatre. This is a wrong way to show flat films. Flat films are often tightly framed, even at 1.85:1. 2.00:1 projection often causes chopped heads and titles. |
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| A 2.39:1 scope image as it should be seen. |
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| The same image, when projected at 2.00:1. Note the loss of image at the left and right. This is a wrong way to show scope films. |
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| The same image, when projected at 1.85:1. Note the loss of image at the left and right. This is a wrong way to show scope films. |