Don't Be Afraid; They Won't Bite: M, P, and S Exposure Modes Demystified

[Below is the first part of a two part article about how to use the different exposure methods that are available on many P&S digital cameras. The aim is to explain the usefulness of each of the modes that come standard on most P&S cameras while taking away some of the panic you might feel about programming your P&S camera.  So, if you're looking to learn more about these modes, then read on.]

The latest digital "point and shoot" (P&S) cameras are truly amazing instruments, able to do just about everything but press the shutter button for you. Actually, if your camera is equipped with a self timer, it will allow you to compose a photograph, run around and insert yourself into the photo and then press the shutter button for you! The degree of automation is extensive, particularly to someone like myself whose first 35mm film camera was fully manual: manual focus, manual shutter speed and manual aperture to come up with proper exposure.  Users had to manually set the camera meter for the speed of the film you were using and manually advance the film after each shot. Today's digital P&S typically offers Auto focus, Auto exposure, Auto ISO, Auto white balance and will keep taking pictures as you keep pressing the shutter button. In addition, many P&Ss offer menus of specialized modes for scenes such as fireworks, backlight, night shots, sunsets, portraits, sports, etc. The camera's settings are then adjusted automatically depending on the mode chosen.

All this automation enables just about anyone to set up their camera for "auto" and make well-exposed photos most of the time, and for many folks this is sufficient. But many P&S cameras offer the shooter the opportunity to exert more influence into the determination of exposure in addition to relying on "auto" or any of the specialized modes. This influence can sometimes produce creativity that may be lacking in purely "auto" shots.

Depending on your particular camera, the standard "auto" mode may be indicated by a symbol resembling the outline of a camera, or some other designator. However, it's not unusual to find a P&S camera that offers "P" (programmed auto), "M" (manual), "S" (shutter priority), and "A" (aperture priority) modes in addition to the "auto" setting or the specialized scene menus. These designations may vary somewhat from manufacturer to manufacturer. Let's look a little closer at each of these modes and see what they might offer.

"P" generally means a programmed auto mode; if you select "P" the camera determines and sets shutter speed and aperture to produce what it considers an optimal exposure. Depending on the particular camera, you may be able to make some additional inputs such as exposure compensation or bracketing, but "P" is still primarily an auto mode and generally produces good results in most situations.

"M" is generally a fully manual mode where the shooter sets both shutter speed and aperture. The camera typically will indicate if the shot will not be optimally exposed at the selected settings; this indication will vary depending on camera brand. You continue to make changes to shutter speed and/or aperture until the camera indicates a proper exposure, then you take the shot. Obviously, some time could be spent finding the shutter/aperture settings that produce the optimal exposure. In most cameras, if for some reason you don't notice that your manual settings are not going to produce a good exposure, the camera WILL NOT prevent you from taking the shot with the wrong exposure. Because of the time it may take to arrive at the proper exposure and the possibility of taking a shot at the wrong exposure, "M" is probably not going to be the mode of choice for most situations. However, if you wish to take long exposures (typically astrophotography of relatively faint objects -- comets, constellations, planets) many cameras will have a "Bulb" setting that will be used in conjunction with "M" to permit the shutter to be kept open for extended periods.

"S" generally indicates "shutter priority" mode -- the shooter sets the desired shutter speed and the camera will set the aperture to produce a proper exposure, or at least it will try to. At first glance, this would seem to be the logical mode with which to set a fast shutter speed to stop action, or a slow shutter speed to cause blurry effects or for use in lower light environments. While this may be true in some cases, "S" mode has the potential to cause exposure problems when selecting fairly slow or fast shutter speeds. Most P&S cameras have a much more limited range of available apertures than their digital single lens reflex (DSLR) counterparts, and this reduces the range of shutter speeds that can be selected in order to produce an optimal exposure. This limited range may be particularly narrow if the camera's lens is zoomed out to telephoto lengths as opposed to being used more as a wide angle.

In photo SP1 (below), I set a shutter speed of 1/15th of a second in order to produce a blurred effect with the water flowing into the pool. Because the P&S was limited to a minimum aperture of f/8, 1/15th of a second caused an overexposure, even on a fairly dark, overcast day. Just as with "M" mode, if you don't notice the camera warning of an improper exposure, the camera WILL NOT prevent you taking the shot with the wrong exposure. The solution here was to set faster shutter speeds until I found one that would produce a good exposure at f/8.

SP1(view large image)

In photo SP2, I set a shutter speed of 1/500th of a second in order to stop or "freeze" the flow of the water into the pool. The camera set an aperture of f/4 and the exposure produced was an accurate representation of the overcast lighting conditions. In this case, "S" mode accomplished my purpose.

(view large image)

Stay tuned for the next chapter, where I complete this discussion by talking about the "A" or aperture priority mode available on the cameras. When using Point and Shoot cameras, this is my favorite mode. The next installment will explain why!

Now published (8/14/2006), part 2: Don't Be Afraid; They Won't Bite: Aaaah, the A Mode and the Perfect Picture