Anamorphic widescreen is a cinematography and photography technique for capturing a widescreen picture on standard 35mm film. It can also refer to a related technique for maximizing picture quality in DVD video recordings.
Figure 1. Without an anamorphic lens, the available film area is not used completely; some of the film surface is wasted on the black bars.
Figure 2. With an anamorphic lens, the picture is stretched to cover the entire film surface, resulting in a better picture quality. When showing the movie, the projector must squish the image back to its original proportions.
Anamorphic widescreen in cinematography was first popularized with CinemaScope, which was one of many widescreen formats developed in the 1950s. The need for anamorphic widescreen arose due to an incompatibility between the aspect ratio of the photographic film, and that of the resulting picture. One common widescreen format has an aspect ratio of 2.35 to 1, meaning the picture width is 2.35 times its height. 35mm film has an aspect ratio of 1.37 to 1, which is not as wide (or, conversely, is too tall). If the picture is recorded on film so that its full width fits within the film frame, some film recording area is wasted on portions that will not be visible in the finished film (Figure 1).
To make full use of the available film, an anamorphic lens is used during recording; this lens effectively stretches the picture vertically so that it fills the available film area (Figure 2). Since a larger film area is being used to record the same picture, quality is increased. The distortion introduced in the picture must be corrected when the film is played back, so another lens is used during projection that returns the picture to its correct proportions.
It may seem that it would be easier to simply use a wider film for recording movies; however, 35mm film was already in widespread use, and it was more economically feasible for film producers and exhibitors to simply attach a special lens to the camera or projector, rather than investing in a new film format, along with the attendant cameras, projectors, and editing equipment.
VistaVision and Cinerama were earlier attempts to solve the problem of incompatible aspect ratios, but anamorphic widescreen eventually proved to be more viable.
The most common anamorphic widescreen film format in use today is commonly called scope or 2.35:1 (sometimes 2.39:1 or 2.4:1). It uses a 2:1 anamorphic projector lens that expands the image by exactly twice the amount horizontally than vertically. This format is essentially the same as CinemaScope except for minor technical differences.
There are artifacts that can occur when using an anamorphic camera lens that do not occur when using an ordinary spherical lens. One is a kind of lens flare that has a long horizontal line usually with a blue tint and is most often visible when there is a bright light, such as from car headlights, in the frame with an otherwise dark scene. This artifact is not always considered to be a problem. It has come to be associated with a certain cinematic look and is in fact sometimes emulated using a special effect in scenes that were not shot using an anamorphic lens.
Another characteristic of anamorphic camera lenses is that out_of_focus elements tend to be blurred more vertically. An out_of_focus point of light in the background will appear as a vertical oval rather than a circle. When the camera shifts focus, there is often a noticeable effect where elements appear to stretch vertically when going out of focus. An anamorphic lens will also have a more shallow depth of field compared to a spherical lens for a given aperture.
While the anamorphic scope widescreen format is still in use as a camera format, it has been losing popularity in favor of flat formats, mainly Super 35. There are several reasons for this:
- An anamorphic lens can create artifacts as described above.
- An anamorphic lens is more expensive than a spherical lens.
- Because the anamorphic scope camera format does not preserve any of the image above and below the scope frame, it may not transfer as well to more narrow aspect ratios such as 4:3 or television.
- Film grain is less of an issue because of the availability of higher quality film stocks and digital intermediates.
Anamorphic scope as a printed film format, however, is well established as the standard for 2.35:1 widescreen projection. Regardless of the camera formats used in filming, the distributed prints will be in anamorphic widescreen format. This is not likely to soon change because cinemas around the world already have an investment in the equipment to project this format.
Other widescreen film formats (commonly 1.85:1 and 1.66:1) are simply cropped in vertical size to produce the widescreen effect, a technique known as masking or hard matte. During filming, part of the picture is masked out, producing a recording similar to that in Figure 1. Some films are shot without a mask, though the film is framed for the intended aspect ratio; this approach is called full frame filming. In these, the film captures additional information that is masked out during projection or video transfer in a soft matte process. This approach allows filmmakers the freedom to include part of the additional picture in a pan and scan transfer of the film, though doing so may introduce areas of the picture that were not intended for viewing, such as microphone booms or other filming accessories that would not have been visible in the widescreen frame.
A similar anamorphic technique is used to store video on DVD. DVDs using anamorphic widescreen make the most effective use of the available resolution, as well as allowing a film to automatically expand to fit widescreen television sets. Widescreen pictures on DVD are stored in a vertically stretched format, in order to maximize the available storage space, and not waste as much on storing the black letterboxing bars. Sources that are close to 16:9 are transferred to DVD taking up the entire 16:9 frame. Sources that are wider than 16:9, such as 2.35:1 video is transferred to DVD with black bars.
When a DVD is inserted into a player, the player will do one of two things depending on the type of television set in use: If the DVD player is set up to output a widescreen image, the player will signal to the TV that the video is anamorphic, and then sends the video, still stretched, to the television, which will stretch it horizontally to fill the screen. The combination of the two stretches involved restore the video back to its original widescreen aspect ratio, minimizing the loss of quality. If the DVD player is setup to output a letterboxed picture, the DVD player squishes the picture vertically to restore the correct aspect ratio, and adds letterbox-style "black-bars" before sending the signal to the TV.
This technique is not used on all DVD discs; some use the standard letterboxing technique. Those that do use the anamorphic technique typically specify "anamorphic widescreen", "enhanced for 16x9", "enhanced for widescreen televisions" or a similar statement on the packaging, though there is currently no widely accepted standard for such labeling. If a DVD claims to be widescreen, but does not have a label like one of the previous, it may use the standard letterbox technique, resulting in decreased resolution for widescreen pictures. Some DVD packaging explicitly mentions that the lower-quality letterbox technique is used; when viewing such a letterboxed DVD on a widescreen display, it may be necessary to zoom in on the picture in order to utilize the full width of the screen.