Filters for color film

Color film filters are mainly for slide film

DIFFERENT FILMS ARE MADE FOR DIFFERENT LIGHT SOURCES

The type of light (daylight or artificial) striking your subject affects the way in which color is rendered on the film and also on the sensor of your digital camera. It’s impossible to make one film that will accurately record color under all light sources, so film manufacturers make some films specifically for shooting under normal daylight and others for photography under artificial light.

Different types of light are identified by their “color temperature” which is expressed in the Kelvin temperature scale (K). (See Light and its color for information on color temperature.)

Daylight film is balanced for light that has a color temperature of 5500K, based on the color temperature of the combined light from the sun and the sky at noon. Type A tungsten film is balanced for standard 500-watt photoflood lamps which have a temperature of 3400K, and Type B tungsten film is balanced for quartz lamps or 500-watt photoflood lamps which have a temperature of 3200K.

When a color film is used with a type of light for which the film is not balanced, (say, daylight film where the subject is illuminated by photofloods) colors will not be properly rendered. However, satisfactory color-balancing can usually be achieved through the use of filters. In other words, by using the correct color-balancing filter, you can use tungsten film in daylight or daylight film under artificial light and still achieve satisfactory color results.

COLOR-BALANCING FILTERS

Color-balancing filters (also sometimes called light balancing, color-conversion [CC], or just conversion filters) convert the temperature of light striking your subject so that it more closely matches the type of film in use. Amber-tinted filters are used for cool lighting, and blue-tinted filters are used for warm lighting. Many filters are available in differing grades, and are usually numbered to indicate their grade (or strength). Usually, the higher the number, the greater the filter's effect. Note that a grade 2 filter is not necessarily twice as strong as a grade 1; it just means it's the next grade up.

Color-balancing filters are far more applicable to color transparency film than to color negative film, since much of the needed color correction can be made when negative film is being printed. However, color-balancing filters can still be used with color negative film since their effects apply equally to either slides or negatives. You will just be making the printer’s job easier.

FILTERS COMMONLY USED WITH DAYLIGHT COLOR FILM

Color film intended for use in daylight can generally be balanced for artificial lighting through the use of the following filters.

• 1A: known as a “skylight” filter, this filter absorbs UV radiation and reduces excessive blue. It is meant primarily for color slide film that is being shot at higher altitudes (aerials and mountain heights), but is also useful on overcast days or in bright shade. Since the filter is almost clear (it has a slightly-rosy tint), no exposure correction is necessary.
• 80A: a blue filter that converts daylight film for use with incandescent tungsten studio lamps (3200K lamps) - filter factor of 4 (increase exposure by 2 stops).
• 80B: a blue filter that converts daylight film for use with photolamps (3400K lamps) that give unfiltered daylight film a yellowish cast - filter factor of 4 (increase exposure by 2 stops).
• 81A: a pale yellow (straw-colored) filter that has a more emphatic effect than the skylight (1A) filter, and is intended for use with electronic flash where the light it casts is too blue. It can also be used as a color-correction filter for tungsten film, and has a filter factor of 1.2 (increase exposure by 1/3 stop). Other filters in the 81 series tend to be brownish and will enhance color portraits by adding warmth to skin tones, making subjects appear to have a healthier, tanned appearance. They are also beneficial on overcast days by increasing overall color saturation.
• 81B: This is probably the most-popular "warming" filter (see note below) and is also used with electronic flash when pictures are consistently too blue.
• 82A: a light blue filter intended to reduce the warmth of early-morning or late-afternoon light by neutralizing its reddish cast - filter factor of 1.2 (increase exposure by 1/3 stop).
• FL-D: also known as FLD (the “D” stands for daylight), FL-Day or FL-W. This filter helps eliminate green cast when using fluorescent light - filter factor of 2 (increase exposure by 1 stop). Another film for use with fluorescent lighting is the CC 30 magenta filter. These filters are also useful for outdoors night-time photography in the city. (See the note below on Fluorescent lighting.)

FILTERS COMMONLY USED WITH TUNGSTEN FILM

Tungsten-type slide films are color-balanced to record optimally at 3200K and 3400K, so photographs made indoors on tungsten film with common household lighting will appear neutral or perhaps slightly warm in color.

• 81A: a light yellow color-balancing filter - filter factor of 1.2 (increase exposure by 1/3 stop).
• 82C: provides slightly-cooler results when using household lamps - filter factor of 1.5 (increase exposure by 2/3 stop).
• 85B: an amber or orange filter that converts tungsten type-B film for use in daylight - filter factor of 1.5 (increase exposure by 2/3 stop.). Without this filter, tungsten film would have a bluish cast when shot in daylight. The amber filter is also useful in removing the blue tinge that results from using daylight film in the shade, under cloudy conditions or indoors using light from a north-facing window in fair weather.
• FL-T: Filters designated FL-T or FL-B help eliminate green cast when using tungsten-type film under fluorescent light. They have a filter factor of 2 (increase exposure by 1 stop).

A NOTE ON WARMING FILTERS

Warming filters, which are sold in a variety of strengths and tonal qualities and can be used with digital cameras as well as traditional film cameras, find all-round use from landscapes to portrait photography. They compensate for excessive blueness in shade, prolong morning light and can enrich the overall tonal quality of images. The Wratten No. 81B is perhaps the most-popular. The 81 series is straw-toned and available in various strengths. A lesser known, but pleasing warming filter is the 85C, which has more of an amber tone and simulates very early or late sunlight. KR series warming filters (from German filter makers) possess a different tonal quality than 81 series filters – it's more of a coral tint, which some photographers prefer, especially for portrait work.

CORAL FILTERS

Coral-tinted filters are available from some manufacturers in a range of gradation from light to heavy. They are used to compensate for the gradual change in color temperature of daylight as the sun travels across the sky, permitting the photographer to match a series of pictures so they all look as if they were taken under identical lighting.

DIDYMIUM FILTER

Also called “enhancing filter,” this filter’s glass contains didymium.

Didymium is a mixture of two elements – praesodymium and neodymium. Neodymium is a rare-earth yellowish metallic element that will combine with other metals or salts to result in rose to violet-colored compounds. Interestingly, the salts of neodymium are used to color the lenses of glassblowers’ goggles to filter out the sodium glare.

The didymium filter increases the saturation of orange, reddish and certain brown objects, making them warm, rich and intense while diminishing or at least having minimal effect on other colors. Scarlet (bright red, tending toward orange) and crimson (deep purplish-red), in particular, are maximized.

Think of the four seasons, and you can probably guess at its principal application, which is autumn photography, when the didymium filter is used for deeply-saturated fall foliage. However, it is also useful at other times of the year, in enhancing the reds in any scene, including sunsets. It can play havoc with skin tones, however, making them excessively warm.

MIXED LIGHTING

Undoubtedly, you will at some time come across lighting conditions that combine different color temperatures – an interior scene, for example, that is lit by both tungsten lamps and daylight streaming through a window, or an early-evening exterior scene that also has a good deal of artificial lighting in it. It is impossible to use one filter for both types of light.

To achieve proper balance for the type of film you are using, you can filter one or the other light source itself using filtering material made from large sheets of acetate film. This is a lot of work, since it's always easier to place a filter in front of the lens instead of the light source.

If you have a hand-held, ambient light meter, you can check to find out which of the lighting types is the dominant light source by measuring the incandescent light then turning it off and measuring the daylight. If the latter is dominant, use daylight-balanced film, especially if the center of interest is illuminated mainly by daylight. The tungsten lighting will still either warm the overall color or just portions of the scene, depending on its influence, but your resultant image should turn out all right. If incandescent light is the dominant source, use tungsten film and expect some bluishness in the areas illuminated mainly by daylight.

If fluorescent lighting enters the mix, your problems are compounded, but the solution is the same, only it is based on measuring the dominance of three lighting sources.

A NOTE ON FLUORESCENT LIGHTING

Lighting from most fluorescent tubes tends to give film a green cast. The exception is the “full-spectrum” fluorescent tube, which gives off a wider, more-balanced light than other fluorescent tubes, and therefore provides acceptable results with color film. Corrective filtration is likely not needed when your subject is illuminated by full-spectrum fluorescent tube lighting, however it is always best to shoot a test roll.

With other fluorescent lights, different coatings on the tubes produce a range of greenish casts, making it almost impossible to predict precise results on film. Although the FL-D and FL-B filters produce good and sometimes excellent results, if absolutely-natural appearing color is a must in your image, you should expose a test roll using different strengths of fluorescent filtration. Keep a record of the filter strengths used for each frame, process the film and compare the results to determine the best filtration method.

Don’t have the time to process a test roll? Don’t give up. There are other options.
1) You can replace the existing fluorescent lights with tubes made especially for photography, like the full spectrum fluorescent lights mentioned above.
(2) You can filter the lights themselves using magenta gels or fluorescent-correcting gels made for the movie industry.
(3) You can switch to a color negative film like Fuji Reala that is made for daylight but performs well under various light sources, including fluorescent lighting, and that can also be color-corrected at the printing stage.
(4) Depending on the type of shot you’re after, you can shut off most or all of the fluorescent lighting, and use flash, or use flash discriminately to overpower the fluorescent lighting in key areas.

OTHER FILTERS FOR COLOR FILM

The sepia tone filter produces a warm brown tone, simulating the appearance of early photographs from the turn of the century. Bright colors may reach the film unchanged, distracting from the desired effect, so subjects should wear muted, monochromatic (different shades of a single color) clothing for the best effect. Beige, light grey, white and tan colors will work best. An exposure increase of two stops is required to compensate for the light absorption of this filter. If you are shooting color negative film, notify the printing lab that the color cast is intentional so they will not attempt to adjust it to more normal tones.

The red filter, normally associated with black and white film, is useful in underwater photography with color film (See Film speed underwater.)

Neutral-density, polarizing, ultraviolet (UV) and a number of other less well-known, color-balancing and special effects filters can be used for color film, and many can be used for both black and white and color film. They can also be quite effective in digital photography.