Dissolve (film projection)
In film projection, a cross-fade is the invisible change from one film projector to another.
background
When a cinema works in so-called reel mode , the entire film (approx. 2500 m for a film of 90 minutes running time) does not usually fit on one reel . Therefore it is divided into several acts , whereby the individual act roles traditionally only have a length of approx. 600 m (corresponds to approx. 20 min. Running time). For this reason, a second projector is required in cinemas without cross-country facilities to ensure an uninterrupted performance.
Another reason for dividing a film into nudes is the previously limited burning time of the carbon arc lamps used in projectors, as well as the previously non-existent possibility of operating coils with a larger diameter (and thus greater weight) with the required active (i.e. electronically regulated) control (The mechanical unwinding friction as well as the purely mechanical slip clutch during winding reach their limits at act lengths of 600 m). There are also practical reasons for transporting a film with a running time of 90 minutes on a single reel: the required 2500 m corresponds to a reel diameter of around 70 cm, while five files of 600 m each are sent in a box of approx. 42 × 42 × 21 cm can be.
An act lasts 15 to 20 minutes. For a 90-minute film, the film copy normally consists of 5 files (around 7 files for 110 minutes), which are distributed on two reels in the projector room on the turntable , provided that the coupling of the film files is permitted (this is not the case with Archive and other valuable copies). If the copy is not allowed to be linked, it must be presented act-wise, which means a corresponding number of fades.
The fade from one projector to another should not be visible to the viewer. Nowadays, large coils (1800–2000 m) are mostly used, so that only a cross-fade is necessary. Operation with projectors that can hold a 5000 m coil, i.e. are combined with a cross-country facility, is an exception.
preparation
For cross-fading, it is important that the correct start and end bands are available at the ends of the nudes intended for cross-fading . If, for example, these were separated for an earlier demonstration with cross-country skiing equipment and were not stuck on again when decoupling, this must be done later.
If the film is now available on several reels, the first reel (with up to four files) is first inserted and shown on a projector. During the projection, the second roll of film (i.e. the spool with the following file (s) of the film) is inserted on the second machine, precisely in such a way that the first film image can be seen in the image window seven seconds later . Before inserting the start tape , the seven seconds at the beginning of the picture are marked. The film is threaded in and transported manually until the marked image is in the image window. The second projector is now ready for the crossfade. If the film consists of more than two film reels, this must be repeated alternately with each additional reel on the film projectors. As the first reel of film on the first projector approaches the end, the presenter has to keep an eye on the upper right corner of the film image on the screen.
The Aktende of the film is determined by the transition character is selected, the short appears in the form of circles, dots, triangles or squares in the upper right corner of the image on the screen. The position of the dissolve characters is internationally defined: The first character (start character or warning sign ) is 193 to 196 frames (corresponds to eight seconds at a film speed of 24 frames per second) in front of the end tape , the second character (dissolve character) is 22 to 25 frames ( around a second) before the end tape (dimensions according to DIN). If the presenter misses the first fade mark, the fade will fail. Thus, the transition characters for the trained eye remains visible, it has a length of four successive images ( 1 / 6 second, longer than a blink). The mark must be in the same place in each frame in relation to the entire film frame . In the past, the cross-fading signs were punched out by the rental company or a film testing company with punch pliers . There are also dissolve marks carved into the photographic layer.
If a dissolve mark is no longer in the right place (e.g. due to mechanical shortening of the film strip), new, correctly counted dissolve marks must be set during preparation. This is done with a (red) grease pencil in the form of discrete short horizontal lines, small dots or small crosses, always in such a way that the trained eye can see them in the upper right corner of the image during projection. When setting a dissolve mark, both the presentation image size ( aspect ratio of the picture window mask ) and the visibility of the dissolve mark must be taken into account. They are more difficult to see on a very dark background or in "wild" images with a lot of movement and many lines. These "hand-made" fade marks must always be applied to the carrier side of the film in order not to damage the photo emulsion . After the last performance, the hand-made characters should be removed with a soft cloth when decoupling the film copy.
Another technical requirement for a successful and “invisible” cross-fading for the audience is that the sharpness of the second projector and its image brightness and light color match that of the first projector. In addition, the image line of the start tape must be checked and correctly set when threading, and the volume on the second projector must be exactly the same as on the first.
process
When the first character (start character / warning sign) appears, the motor of the second projector is switched on immediately. If the projection lamp is not already switched on, it will also be ignited. If the second sign (cross-fading sign) appears, the projectionist has about one second to let the actors speak, switch the sound and open the image flap (an opaque flap in the beam path) on the second projector.
As soon as the second projector is switched to and projects, the picture flap of the first projector is closed so that the projected images that are still running cannot reach the screen. If the image and sound only get into the cinema from the second projector, the cross-fading is successful. In the best case scenario, the cross-fade succeeds without the audience noticing the switch.
It is possible to automate the process, for example using a matrix machine . Here, aluminum foil glued to the film (see picture) or barcode stickers at the end of the expiring act initiate the transition.