Film

You know that there's black-and-white film and color film, print film and slide film. We'll definitely consider the pros and cons of each. But, in harmony with our theme of predicting how our camera sees, we must also examine how different kinds of film record light differently.

Some are more sensitive to light than others, but that is just the beginning. Light itself comes as a spectrum of colors, so we can expect that some films will be more sensitive to one end of the spectrum and others will be more sensitive to the other, and so on.

After reading this page, you should be well prepared to select whichever film best serves your creative purposes.

Films are classified by their speed. No, the film doesn't move; speed is a way of describing how light-sensitive it is. Really, it's called speed because it's an indication of how fast of a shutter speed you can use to expose the film a given amount. Fast films are very light-sensitive, so you can adequately expose the film with a fast shutter speed (or a narrow aperture). On the other hand, slow films require more light, so you must use a slower shutter speed or a wider aperture to adequately expose it.

The International Standards Organization (ISO), has made film speed easy to describe. Instead of using complex scientific units, we just use an ISO number, like ISO 100 or ISO 400. Typical values for 35 mm film are 25, 50, 64, 100, 200, 400, 800 and occasionally 1600. Intuitively, the higher the number, the faster the speed, and the more light-sensitive the film is.

The mathematically oriented among you will have noticed a pattern by now: With the negligible exception of 64 (since it's close to 50), each ISO number is twice the previous one, just as each shutter speed is twice the previous one and each f-stop doubles the entering light intensity. In fact, doubling the ISO number is equivalent to going up one f-stop or halving your shutter speed, meaning that you compensate for double the film speed by stopping down one or by doubling your shutter speed. This all works nicely because the range of light intensities that our eyes and film are sensitive to fits on a logarithmic scale (base 2), not a linear one.

If you use a point-and-click camera, you usually can't adjust the aperture or shutter speed; they are usually set at a relatively narrow aperture and medium-high shutter speed, so selecting the proper film speed is the most important adaptation you can make, especially since your flash is almost always useless in nature photography. You will find a guide to using 100, 200, and 400 speed films on the film package. You will also find it here:

• ISO 100: For a point-and-click, 100 will be underexposed in all but the brightest conditions, meaning full sun. However, if you use an SLR you have enormous flexibility with this speed, and it is usually my film of choice.
• ISO 200: An all-purpose speed, useful for most kinds of weather conditions, but with a point-and-click this speed is not for twilight unless you want silhouetting.
• ISO 400: Likely to overexpose your film in bright sun, unless you use, say, f-16 or f-22 and 1/500 or 1/1000 sec shutter speed, underexposing more than your point-and-click might do. I usually have to stop my camera all the way down on bright days to avoid overexposure. This takes away the option of minimizing depth of field or using longer exposures, which for certain effects are often desirable. However, with a point-and-click especially, 400 gives you the most flexibility to deal with varied light conditions such as stormy weather, deep forest, early morning, and twilight.

For serious nature photography, you may want an even lower speed than 100, because in low light you can often just decrease your shutter speed and open your aperture if you use a tripod. Professional film is probably your only option in this case: For example, Fujichrome Velvia has a speed of 50, and Ektachrome 64 Professional EPX and Kodachrome 64 are, to our great surprise, ISO 64. Kodachrome also comes in ISO 25. You may also be interested in black-and-white film. It comes in most of the standard speeds also.

  Film Pros and Cons

Professional photographers use several different cameras at a time, each loaded with a different film, so they can use the best one for the occasion, because different film brands are sensitive to different ends of the color spectrum. For those of us without that kind of budget, however, utilizing those effects is more of an optimization than a necessity, so we will postpone our discussion of it 'til we study color. For now, we will consider the pros and cons of black-and-white, print, and slide film.

Black and White
Despite the color film revolution, many photographers continue to prefer black-and-white for its very fine grain and the certain classic artistic sense it conveys. It also is equally sensitive to the full range of color tones, presenting them in an accurate grayscale. The disadvantage is no color, of course.

Color Prints
Compared with slides, print film tends to produce more subdued colors, an effect some photographers dislike while others claim presents the scene more naturally. Also, in a sense you make two exposures: one of the film and the other of the paper. This allows you to correct small exposure mistakes when you make your prints. Of course, since most of us don't have our own darkroom, I highly recommend that if the processing company exposes any of your prints differently from how you expect, under- or over-exposing them to produce an undesired effect, you ask them to reprint them for free. If they have any business sense, they probably will; they have for me. The main disadvantage to print film is that the grain is not quite as fine as with slide and B&W film. However, a large-format camera can make up for this.

Color Slides
This is the film of choice if you want to publish; the slides are cheaper and easier to transfer to books and magazines. Furthermore, you get the finest grain and most vibrant color rendition with slides, although some argue, as I said above, that subdued colors are more natural. If you like vibrant colors, then, the only real disadvantage to slides is that you might want prints! But you can make prints from slides; it's just more expensive than printing from negatives.

You be the judge; you experiment. I have not personally used every film extensively, so I'm taking some of this information from books written by more experienced photographers. This means your job is not to just read this site but to try things out for yourself. Anyway, isn't that the point?

  Determining the Light Intensity

After experimenting upon what we've covered so far, you should be well prepared to make accurate exposures that neither wash out nor blacken the colors in your photographs—except for one extremely important thing: we know all about how to contol the light entering the camera, once we know the incoming light's intensity. But hopefully you have noticed we have said nothing about how to determine exactly what that intensity is and how that translates into an f-stop/shutter speed combination at your particular film speed. On the next page, we will learn all about that. With the right tools it's easier than it sounds.