For Outdoor Photography
Whether you're photographing in color or black and white, there are filters that, placed over your lens, can help you achieve the best possible results under the specific conditions for which they are intended. Filters change the color, quantity and the quality of the light that passes through your lens. Some are intended for use with black and white film, some for color, and others may be used with both.
Filters are basically available in two forms. One is the screw-in type that fits into the threads on the front of your lens barrel so that it appears to become another element of the lens itself. This is the traditional form, and its only drawbacks are: (1) If you have several lenses with different diameter lens barrels, you will either have to buy a set of filters for each lens diameter, or buy a set that will fit your largest lens and use adapter rings to make them fit the other lenses. (2) These filters are made of glass which can break. If that were to happen, it could scratch your front lens element.
The other form is a flat plastic square or rectangle (Cokin is the most commonly known brand, but there are others) that fits into an adapter that can be used on all your lenses, provided you buy the proper size adapter and the required adapter rings to mount it to your lenses. Generally, this is a more economical way to buy filters. (Similar to the plastic filters are the Gelatin filters. These have become quite expensive in recent years and they require great care in handling, for they can be warped by heat, easily scratched and are not as easy to clean as the other types. I do not recommend them for photographers who work outdoors.)
By function, there are five kinds of filters--(1) polarizing (2) contrast control, (3) neutral density, (4) color correction and (5) special effect. Probably the single most useful of these is the polarizing filter.
I have often said that if I could afford only one filter it would be a polarizer. A polarizer works with both black and white and color film, eliminates glare, produces greater color saturation, and darkens skies. It also can be used as a neutral density filter (see below). Glare reduction is optimized when the camera is placed at a 45º angle to the reflecting surface, and darker skies are produced best when you are shooting in a direction 90º from the position of the sun. Rotating the filter around its axis will also change the degree of polarization and this effect can be observed through the viewfinder of your SLR or on the ground glass of your view camera.
Contrast control filters are the ones we use mostly with black and white film. The most commonly used are yellow, orange, red, green, and blue. These, by transmitting their own color and blocking a portion of their complementary color (opposite on the color wheel), will alter contrast and change the way certain colors are rendered on black and white film.
For example, panchromatic black and white films (generally, the ones you use for normal photography--not infrared or graphic arts films) will produce similar gray values for green and red. You can separate these colors (through contrast) by using a green filter to admit more green and less red light. This will render the green areas darker on the film and lighter in the print, while doing the opposite to the red areas. (Green filters also have little or no effect on Caucasian skin tones and can be used effectively in outdoor portraiture.)
Yellow, orange and red filters are the ones most often used to produce darker skies in black and white photography. Yellow darkens the least, but generally provides better definition between clouds and open sky than you'd get without a filter. Orange filters produce more dramatic skies and greater cloud definition, and red can be used to produce a black sky, especially when combined with a polarizer. Red filters, with nominal underexposure during daylight hours will produce a nighttime effect.
Blue is probably used less often by black and white photographers, but it can produce some very nice effects with subjects such as old weathered wood that tends to take on a blue-gray cast. There are also occasions when one prefers a lighter sky--can you think of any?
Neutral density filters compensate for excess light by reducing all the colors of light that pass through them equally. You might use a neutral density filter when your camera is loaded with high speed film to permit the use of a larger aperture or a slower shutter speed in a brightly illuminated environment. It would have no effect at all on the way colors are rendered on either black and white or color film--it would only give you a lower effective film speed by blocking out a specific quantity of light.
Color correction filters have several uses. Generally, when we think of these, we think of the ones that permit you to use tungsten balanced color film when working in sunlight and vice versa. But there are many more color correction filters for specific applications.
Black and white photographers
don't need to worry about color correction (unlessand this
is strictly esotericayou're using a film with extended
sensitivity to a particular color and you want to alter its range.
The last group of filters are the special effect filters. These will produce stars, kaleidoscopic effects, action lines, false sunsets, bizarre colors, fog, vignettes, and many other results limited only by your own abilities and imagination.
There is one special effect filter that I find especially useful in landscape photography. It is the split neutral density filter. Half of it is gray and half of it is clear. The gray is "feathered" where it meets the clear portion so that when you shoot through it you don't see a line where the two values meet. The gray part holds back light of all colors equally, while the clear part transmits everything.
I use the split neutral density filter when I am faced with a subject that includes a foreground that contrasts too harshly with the background (or vice versa). This permits me to retain desired detail in both areas. Without the split ND filter, you can only compromise, and some value has to give.
For example, on a sunny day in Colorado, the sky is usually much brighter than a conifer forest. If both sky and forest are important to the picture you're trying to make and you want to retain good sky color as well as forest detail, you can use the split ND filter to hold back some of the light from the sky while exposing the forest portion of the image normally. You can slide the filter up and down in the mount to use just the right amount of neutral density where it is needed.
When photographing in black and white, this filter is just as valuable, if not more so, than it is when you're working in color. Where once we had to control such contrast through development and manipulation in printing, we can now produce negatives with a much more "printable" range of tones. You eliminate the need for excessive dodging and burning by reducing (in our example above) the sky density and increasing the density of the forest detail in the negative.
Now you're probably asking, "Should I buy a bunch of filters before this workshop?"
Let me answer that first for those of you who already own some filters. If you want to add to your collection, I suggest you go slowly at this point. You probably have a polarizer and two or three contrast filters for black and white photography. That's enough for this workshop, but you may want to try a split ND filter (like Cokin's 120 or 121). If you don't have a polarizer, that would be a good investment at this time.
If you aren't currently using filters and don't own any, I suggest you buy a polarizer (get a good one--I know they're more expensive than the other filters, but cheap polarizers are rarely worth even what you pay for them. Don't let a discount store tell you that their brand X is just as good as a Cokin or Tiffen or B&W.) And for now, if you want to be careful and try just one contrast filter for black and white, buy a deep yellow or medium orange filter. I'd rather you approached the use of filters slowly and carefully. Learn what just two can do and then add to your arsenal. The polarizer and the one contrast filter will get you through this workshop nicely and you won't be so preoccupied with your new toys that they get in the way of your seeing good compositions.
To use or not to use UV filters? It probably isn't a bad idea for most of you, even if it is only for protection of the more expensive glass behind it.
Finally, it should be said that there are some photographers who never use filters and do quite well without them. I don't happen to subscribe to their brand of "purism," but they have a right to their point of view, and I agree that filters are not a panacea. Some photographers rely on them too much.
Remember, we'll be talking about filters during the course of the workshop and you'll have ample opportunity to ask questions and see samples of what filters can do for you.