Bruce Barnbaum - The Art of Photography - An Approach to Personal Expression

A yellow filter requires only a ½ or 1 stop exposure increase, as it is weaker than a red filter. It should be pointed out that even with the appropriate filter factor for correct exposure, a red filter will darken blue far more than a yellow filter because it impedes blue more thoroughly than the weaker yellow filter.

The filter factor is correct only if the scene contains a broad spectrum of color. For example, if a scene is dominated by red and a red filter is used, little exposure increase is necessary because all red wavelengths would pass through the filter unimpeded. However, if a red filter is used on a scene that is dominated by green, an exposure increase of more than three stops would be necessary because a high percentage of the wavelengths would be stopped by the filter. Thus, the filter factor represents a starting point for the average scene. It must be increased or decreased as appropriate if the scene diverges greatly from the theoretical standard.

Examples with a Hypothetical Landscape

Walk with me into an idyllic landscape and consider the effect of various filters on it. The foreground is a rolling pasture of luxuriant green grass with a background of low hills and distant mountains. A red barn is off to one side, large orange poppies dot the foreground grass, and a deep blue sky with fleecy white clouds tops the scene. It is a hypothetical scene that possesses just about every color, so playing with filters can be an interesting exercise. Following are some of the possible effects of using (or not using) filters on such as seen:

Using no filter with any of the common panchromatic films (which have a higher sensitivity to blue light than our own eyes), the sky would come out as light gray. The clouds would not stand out strongly against the light tonalities of the sky, and the distant mountains would also be rather light due to the bluish atmospheric haze—however slight that haze may appear—and therefore would not be terribly outstanding. The barn would be dark, as would the grass, while the poppies would stand out as light gray dots.

With a light yellow filter (#8 or K2), the sky would be darkened to the gray value that your eye would tend to expect. The clouds would be more visible against the darker gray, and the distant mountains would also be somewhat more visible due to the reduction in blue haze. The grass would be slightly lightened and the poppies would be lightened even more, while the barn would be slightly darkened, separating it somewhat from the grass tones. A deeper #12 yellow filter would darken the sky considerably, making the clouds pop out more strongly. Again, the grass would be lightened to about the same extent as with the K2 filter, but the poppies would be made even a bit brighter against the grass. The barn would be darker than with the K2 filter.

A #21 orange filter would darken the sky considerably, bringing out the clouds quite strongly, and the mountains would also be darkened. The orange poppies would be nearly white against darkened grass, and the barn would be slightly lighter than the grass.

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.