CC filters are available as thin gels, somewhat like thick cellophane sheets, which are placed in front of the lens like any other filter. The filters alter the color balance of the scene, shifting it toward the color of the filter just as if they were cellophane sheets—except the filter’s shift is quite subtle.
In the previous chapter, I pointed out that outdoor color film tends to shift toward blue in the shadows or under cloudy conditions. This can be an advantage at times, but it can be harmful as well. Color correction filters can neutralize this blue shift (Figure 7-3 and Figure 7-3). My own experience shows that a combination of CC10M and CC05Y, or alternately, CC10Y and CC05M, returns the color shift to the colors I see. If I want to subtly emphasize yellows or greens in the transparency, I use the CC10Y + CC05M combination, but if I want to bring out warmer tones, I tend to use the CC10M + CC05Y combination. I have used the two combinations often when photographing the deep, red-walled canyons of Utah and Arizona (Figure 7-4).
In this deep canyon of Northern Arizona, I combined CC10M and CC05Y filters to warm the scene. The major emphasis was on warming the walls and tree trunk to prevent a blue cast.
Figure 7-4. Shiva the Dancer, Paria Canyon
CC filters can be used not only to neutralize unwanted color shifts, but also to enhance moods by enriching colors. Suppose you have a composition dominated by green leaves, but they are rather dull in color. A combination of yellow and green CC filters could lighten and enliven the colors. In a similar way, slight amounts of red CC filtration could warm skin tones for portraits—or, you could do a variation on Newman’s portrait of Krupp by using a green CC filter for a more macabre look! Only the slightest amounts of filtration (CC05 or CC10) should be used, or the results may look too contrived.
It takes some time, and a good feel for mood, to learn how to effectively use CC filters, but the emotional shifts they can create are quite remarkable. The emotional connotations of slight color variations have extraordinary impact. CC filters should be an indispensible part of any serious color photographer’s tool kit.
An abundance of other filters can be used for color filtration. The most well known are the haze, skylight, and ultraviolet (UV) filters, which correct for the blue cast of ultraviolet light in bright sun or high altitudes. Film responds strongly to UV light. Since the eye compensates and we tend not to see the blue shift, these correction filters can be very valuable in reducing the blue.
Many people place a filter permanently on the lens, feeling that the correction is proper and that the filter affords protection from damage in case of an accident. This strikes me as a strange approach. First, permanent use of a filter reduces options for later filtration. Second, if the film looks better with the filter on permanently, it may indicate that you should seek another film with a more pleasing color balance. Finally, if you need protection from lens damage, it may indicate that you are too careless and should change your habits, pronto!
One final note on color filtration: CC filters can be combined in extremely high levels to correct for the green shift of fluorescent lighting. However, there are many different types of fluorescent lights, and each requires its own filtration packet. You can write to Kodak or Fuji and obtain their booklet explaining fluorescent filtration. As an example, the appropriate filtration for old Ektachrome or current Fujichrome indoor 4 × 5 transparency film is CC50M + CC60Y for “cool white” fluorescent, with a filter factor of 2 stops. This is a great amount of filtration, but since it does negate the unpleasant green shift associated with fluorescent lighting, it’s worth using.
Many digital cameras avoid this issue entirely with an automatic white balance feature that recognizes fluorescent lighting and rebalances color for it. On some cameras, you have to do it manually. Either way, it’s a valuable feature, one that removes a lot of guesswork and discolored images that can be the bane of traditional color films. Of course, fluorescent lighting is never a problem with black-and-white film because it sees only light levels, not colors.
Neutral Density and Polarizing Filters
Two types of filters are useful for both black-and-white (including infrared) and color photography: neutral density and polarizing filters. The neutral density filter essentially amounts to putting sunglasses on your camera. It cuts the amount of light entering the lens equally from all parts of the visible spectrum. It does not alter color balance, nor does it selectively block specific color wavelengths while allowing others to pass unimpeded. Its purpose is to force longer exposures.
Neutral density filters allow anything from slight exposure increases (1-stop neutral density filters) to extreme exposure increases (10-stop neutral density filters). This may seem like a strange approach considering today’s emphasis on faster films and lenses (i.e., lenses with wider maximum apertures), but it does have wonderful uses. Consider the example of Wynne Bullock’s extended time studies cited in Chapter 3. I don’t know whether Bullock’s exposures were made at dawn or dusk under low light levels, or whether he artificially created long exposures at midday through the use of neutral density filters, but the effect is magical. It could not have been done with standard exposures.
Most photography today emphasizes stopped motion; but if you are interested in exploring the effects that motion can produce under long exposures, neutral density filters are mandatory. They can be expressive and creative tools with more applications than most photographers realize (Figure 3-16).
Two light waves travel along the Z-axis from left to right. Light wave #1 is in the X-Z plane (the vertical plane), perpendicular to the Y-axis. Light wave #2 is in the Y-Z plane (the horizontal plane) perpendicular to the X-axis. The “pickets” of the polarizer are aligned parallel to the X-axis (i.e., vertically). Light wave #1 passes through the filter. Light wave #2 is stopped, for its angle of orientation is 90 degrees to that of the filter.
Figure 7-5. The Polarizer—How It Works
The polarizing filter (or polarizer) is a neutral density filter with a 2-stop filter factor. Beyond that, it reduces glare, which is highly polarized light. In order to understand what a polarizer does, we must first understand what polarized light is. Again, we must become somewhat technical, but not very much so.
For our purposes, we can say that light propagates as waves from its source (the objects in the scene) to the receptor (your eye, the camera lens, etc.). If you drew a straight line through space from the source to the receptor, there would be millions or billions of light waves traveling along that line. Each individual wave would be oriented at a slightly different angle to the direction of travel. Most objects emit or reflect nonpolarized light, in which approximately equal numbers of waves are oriented at any given angle to the direction of travel. Some objects emit or reflect polarized light, in which most waves are oriented in one plane perpendicular to the direction of travel. If we drew a coordinate system in space, with X, Y, and Z axes at 90 degrees to one another, and polarized light traveled along the Z-axis from left to right, there would be a predominance of waves in the X-Z plane (i.e., the vertical plane) compared to the Y-Z plane (i.e., the horizontal plane).
In a sense, the polarizer acts as a visual “picket fence”, allowing only waves oriented in the same direction as the pickets to pass through the filter. Therefore, if the pickets are parallel to the X-axis, waves in the X-Z plane pass through while those in the Y-Z plane are stopped. If the polarizer is turned 90 degrees so that the pickets are parallel to the Y-axis, then waves oriented in the X-Z plane are stopped and those in the Y-Z plane pass through. Those at intermediate angles pass through in direct proportion to their closeness to the angle of the pickets.