1963 – 1977
Subtractive 3 color: Chromogenic monopack, 16mm and 35mm reversal
Original Technical Papers and Primary Sources
Anonymous (1961): What is Color Correction? In: American Cinematographer, 42,2, Feb. 1961, p. 104 and p. 108.
“What is Color Correction?
The Importance of color correction in the process of printing or duplicating color films is something not to well understood by many who photograph and produce 16mm color motion pictures.
“Apparently the term means different things to different people,” suggests General Film Rewind in its December, 1960, issue from which the following information is excerpted:
The University Film Producers Association Nomenclature Committee in its listing of “16mm Terms” (journal of the UFPA, Winter, 1960, issue) gives the following definition:
Color Correction: –1: Alteration of tonal values of colored objects or images by the use of light filters, either with the camera or printer. 2: Lens design which corrects chromatic aberration.
Color correction doesn’t pose too much of a problem in 35mm color work, the Rewind points out; the confusion centers on 16mm color – probably because of the different materials, and therefore, different process which are involved.
In 35mm, the article explains, a color negative is exposed from which 35mm color positives are made – either release prints or an interpositive from which is made the 35mm color internegative. To correct color, each scene is judged against a norm, with a color timer actually viewing how the scene would appear with the normal printing light, and with changes in color achieved by varying the proportion of the three primary colors. The color corrections, or changes, are then achieved in printing a positive direct from the camera negative. This system works rather well, and there is little occasion for review of the results.
However, in 16mm color we have quite a different situation. First, the film exposed in the camera is a color reversal-positive, such as Eastman Kodak’s Ektachrome 16mm film. The selected scenes of the processed camera film are usually edited in A&B rolls, to set up for the use of fade and dissolves in printing. From the edited A&B rolls may be made 1) direct reversal color prints, or 2) a 16mm color internegative to be used in making color positive prints.1 In the first method, both camera and dupe stock are similar. In the second method the negative-positive color duplicating stock is basically different from the reversal camera stock.
Color correction in 16mm film printing is accomplished by the same basic method as in 35mm – by varying the proportion of light from the three primary colors.
So, where does the confusion come in?
On three different points – the mechanical method (How is it done?), the process (What is accomplished?), and on cost (Why does it cost more?).
First, method – How is it done?
The color may be altered, between original film and dupe, by either of two basic methods – known as “subtractive color printing” and “additive color printing.” The former utilizes a single light source in the printer, and the color is varied by the insertion of a filter in the light path. In effect, the filler serves to screen out, or subtract undesirable color variations in the print. If the scene to be printed is too red, the filter will reduce the red values in the normal printing light, allowing more blue and green to come through.
Additive color printing utilizes three separate light sources, each representing one of the primary colors. By varying the quantity of light from, each of the three beams, a new “color mixture” is achieved in the light exposing the dupe stock, and the color tone or separate color content is thus varied within the scene.
Both subtractive and additive systems are used, and each can do a satisfactory job. However, it is generally believed that the additive method provides a greater degree of control. Next, process – What is accomplished?
This is the area of greatest confusion for users of 16mm color film – both as regards just what is done, and how this affects the print. Each of the following operations has been referred to as involving color correction:
Normal timing (measuring of the over- or under-exposure of each scene), and alteration of the volume of the printer light during the printing process to lighten dark scenes, darken light scenes. The purpose is to achieve a more even exposure of the scenes in the print, and professional timing does result in a better looking print. But, it is not intended to alter color tones in printing.
The use of a single filter in printing a show edited from one emulsion, as recommended by the film manufacturer or indicated by laboratory tests, to achieve more normal and desirable over-all color balance in the print.
The use of a filter, or filters, to change the color duplication of a few scenes which are noticeably off-color (usually resulting from exposing daylight film with artificial light, or vice versa, or similar camera errors). This may involve one to a half dozen or so scenes, scattered throughout the edited roll.
The use of filtered light in printing to affect the color duplication of every scene in the edited film. This is “scene-to-scene” color correction – each scene being “read” or judged for color in the same manner it is read or judged for density.
Now, only two of these operations involve color correction. Number 3 might be termed ”problem scene color correction.” Only Number 4 is color correction in the professional sense a scene-by-scene judging of color balance, with the necessary changes made in the additive color printer to achieve a smoothly balanced print.
Obviously, the results achieved will vary with the type of handling, as outlined above. This is one reason why opinions vary so in the 16mm field – we use the term “color correction” in referring to different methods.
This brings us directly to the cost factor – why does it cost more? Here, again, it depends on which of the methods we are considering. There’s no additional charge involved in normal timing of prints, with the resultant variation of the quantity of printer light utilized on printing the different scenes. As mentioned above, the only purpose of this light adjustment is to darken light scenes and lighten dark scenes. Usually the service of preparing for and doing the normal type of release printing is included in the listed price of the print. (In the making of 16mm color workprints, there’s a small additional charge for making a timed color workprint, as compared with the price of a one light color workprint.)
Similarly, most film labs make no additional charge where a single filter is used in a printer to affect the over-all beginning-to-end length of the print. This is a normal requirement included in the usual price of a print.
When laboratories encounter what they call “problem scene color correction,” this involves special handling and additional work, which usually leads to additional costs. It’s possible to set up a printer to vary the color balance of the printing light only for the specific problem scenes, but this requires almost as much time as setting up for color timing of each individual scene. It also requires the use of a specialized additive color printer which is much slower in operation than a standard production printer. The laboratory has two options – omit any charge and absorb the additional cost, or charge on the same basis as for a fully color corrected print.
Fortunately, there’s another simpler and less expensive method for accomplishing the same end-result, if the producer is aware of this possibility and edits his film accordingly. The problem scenes which require similar color correction may all be edited on a third or “C” printing roll. This permits the use of a single filter to achieve the desired color balance for that roll, and the print is charged for on AB&C roll basis – considerably less than the cost of A&B roll scene-to-scene color correction.
When a film is to be set up for scene-to-scene color correction, the individual scenes must be judged, not only for density (involving the total quantity of light to be used in printing), but also for color balance (involving the choice and preparation of the primary color mixture to be used in printing). This involves the judgment of an experienced color timer, the use of specialized equipment, and the setting up of separate control strips for the printer. Then, the edited film rolls are put on an additive color printer, which is considerably slower in operation than standard production printers. Time is the basic cost factor in any business operation, so slower speed in printing means increased cost of production.
Since motion picture printing is a combination of science, art, and personnel opinion, the making of a fully satisfactory color-corrected print may be achieved with the first print, or it may not. It’s entirely possible that two, three or more prints may have to be made where originals involve difficult color-correction problems. Obviously, this, too, adds to the basic costs involved.
Thus far we have been discussing color-correcting the 16mm color reversal print made from a 16mm color reversal original. The same basic factors are involved when the color reversal originals are to be translated into a 16mm color internegative for color positive release printing. Since the color systems are somewhat different, the results of color correction may vary. That is, the same filter that produced a desirable result from a scene reproduced on color reversal film may not provide a satisfactory result in a color positive print. If not, there are two alternative laboratory procedures possible. Either start all over again and make a new color infernegative, or introduce color timing in printing from the existing color internegative. Each procedure involves cost. If a new internegative is made, the costs involved are raw stock, labor, and overhead. If the same internegative is to be used, with additional color correction to be made in printing, the printing speed factor again enters – since the internegative must be taken off the faster production printer and put on the slower color-correction printer.
“In our experience,” says General Film Laboratories, “35mm color negative clearly requires color-correction, and correcting of color is an apparently stable and satisfactory process. The well-exposed 16mm color reversal original film does not require color-correction, except for the occasional problem scene. To judge by the requirements and requests of customers, color correction is standard in 35mm work, but little required in 16mm work. However, like so many occasional requirements, 16mm color-correction is a lifesaver when you really need it!”
1 Also possible to make a 16mm color reversal master from which contact second generation prints can be made. However, this method is little used now that 16mm color internegative-positive process is available – except for special purpose requirements.
(Anonymous (1961): What is Color Correction? In: American Cinematographer, 42,2, Feb. 1961, p. 104 and p. 108.)