A #25 red filter would turn the sky dramatically dark. The white clouds would jump out boldly, and the mountains would be even more visible, as atmospheric haze would be cut to a minimum. The orange poppies would be quite light, but the grass would be even darker than with an orange filter—so the contrast between the two would remain about the same as it is with the orange filter. The red barn, however, would appear quite light, and if it were a newly painted, bright red, it could be rendered nearly white! If it were a typically dark red barn, weathered and unpainted for many years, it would still be lightened significantly. A somewhat less intense #23 red filter would slightly subdue each of these effects; an even stronger #29 red filter could dramatically intensify them.
Before looking into the effect of green and blue filters on the scene (and you are certainly permitted to think about them before reading on!) consider the most appropriate filter among those discussed. Recall the general mood of the scene, which is one of vivid colors and crispness, yet one of peace and restfulness. The red filter would be too strong for me because it overdramatizes the scene and the mood. I would want my gray tonalities to be rich and brilliant, but not so sharply rich and brilliant. Without any filter, the photograph would be rather bland, lacking the required crispness that I feel the scene deserves. Thus, for me, it comes down to a choice between the yellow and orange filters. I will make my choice, you make yours!
Back to the remaining filters:
A green filter would slightly darken the sky, about as much as the K2 filter, but it would lighten the grass and darken the poppies. The barn would be darkened considerably, which could be interesting. However, the effect it would have on the grass and poppies would be highly unpleasant to me, and I would avoid its use.
A blue filter, in my opinion, would be utterly inappropriate, for it would turn the sky almost white and do much the same for the mountains. The clouds would effectively disappear. The barn would be dark gray, while the grass and poppies would be nearly equivalent mid-gray tonalities. That is not the effect I would seek.
Those are my opinions about the desirability of each filter in a hypothetical scene. You may prefer one of the other effects, perhaps even the last one that I rejected so thoroughly. You may wish to concentrate your vision on only a small portion of the scene, rather than the full panorama, and use a different filter to alter its qualities. Your approach could be perfectly wonderful and could show great insight. There is no “right way”. There are many things to consider, and they should all be considered.
Keep in mind the fact that all black-and-white filters perform two tasks: they make their own color (as well as closely related colors) relatively lighter, and they turn other colors darker. (Actually, they only darken colors away from themselves on the color wheel—progressively more for colors toward the opposite side of the color wheel from that of the filter.)
Both effects must be considered on all parts of the scene and all elements of the photograph before the exposure is made. Too often the careless photographer considers only the prime purpose of the filter, without considering its side effects on other areas of the photograph. You may commonly find the most appropriate filter to be a compromise choice. The best filter for one purpose—the primary purpose—may be decidedly harmful to other aspects of the image, whereas a filter that is not quite as effective for the primary purpose could be either neutral or helpful to secondary effects (Figure 7-1).
Filters are important aids in black-and-white because the effects they produce cannot be duplicated by even the most intricate darkroom maneuvers. Imagine trying to photograph the hypothetical scene of the previous example without a filter, and then in the darkroom attempting to darken the sky without darkening the clouds, or brightening each poppy without brightening the grass! It would be a miserable task, indeed.
Contrast Control with Filters
At the same time that filters alter the relative tonalities of objects based on their colors, they also change contrast between objects. They can actually alter the composition by directing the viewer’s eye toward objects or areas that are accentuated and away from those areas subdued by filtration. Thus, they are important compositional tools. A #25 red filter increases contrast in a landscape because it cuts through the blue atmospheric haze, even when the air seems crystal clear. A #12 deep yellow filter has a similar, but milder, effect because it also cuts through blue haze very effectively (Figure 7-2 and Figure 7-2). I consider the effect that filters may have whenever I set up my camera for a photograph, even though I may use them in only a small percentage of instances. I feel that landscapes can benefit most from thoughtful filtration because colors are so unsaturated in nature, and therefore have a tendency to be rather gray under soft lighting. With filters, tonal variations may be separated with clarity.
Not only can filters be used to separate tones, but they can also be used to bring diverse tones closer together—as the green filter brought the grass and poppies together in the hypothetical example above. Jay Dusard often uses filters in this manner, separating the tonalities later in a very different manner during negative development. There may be times when a darker or lighter color can be intrusive or disruptive to a composition, and it can be better blended with its surroundings through filtration.
An example drawn from my experiences in the Utah/Arizona canyon country helps explain this idea. The dominant features of the landscape in that area are the enormous sandstone cliff faces. Some cliffs that are nearly white in color have visible horizontal lines of various red/purple hues caused by the stratification of ancient dunes or clay deposits. They also have dark, vertical eroded crevices caused by water pouring down the cliffs. Photographing these cliffs with a green filter further darkens the horizontal streaks, making them the dominant feature. A red filter, however, lightens the horizontal streaks almost to the point of tonal merger with the rest of the cliff. When the horizontal streaks nearly disappear, the vertical eroded crevices become the dominant feature. Thus, the choice of filter can potentially change the dominant line structure of the image from vertical to horizontal!
Just as with any other aspect of photography, no two photographers will have the same approach. This is the meaning of personal expression, and it is as it should be! The important thing is to use your tools with understanding and with a purpose in mind. Filters can be exceptionally useful tools.
Digital Filtration for Black-and-White
The approach that digital photography takes to filtration is quite different. Using a digital camera, all photographs can be—and most logically are—initially made in color. The color is rendered through three separate channels: red, green, and blue (RGB). Later, at the computer, the image can be broken down into each of those channels, allowing you to choose one channel or percentages of all three channels for the final photograph. Furthermore, the image can be broken down into sections so that different percentages of the channels can be used in different portions of the print. This process can be the rough equivalent of filtering one portion of the image with the most appropriate filter for that section alone (perhaps a red filter for a sky with billowing clouds) and another portion of the image with a different filter (perhaps a green filter for the grasses and trees). It can be tedious, of course, but it allows for extreme control.
With traditional photography, it would be possible (though highly impractical) to make two exposures in the field with different filters, then print one portion of the final image using the negative that benefits from the first filter and the remainder of the image from the negative that benefits from the other filter. Pin registration of the two negatives (Chapter 10) would be required.