Modern cameras are equipped with a built-in exposure meter, which is able to automatically assess the level of illumination and select the appropriate values of the exposure parameters. If the exposure value offered by the exposure meter does not suit the photographer, he can either switch to manual mode and set the exposure independently, or, while remaining in automatic mode, use exposure correction. Exposure correction or exposure compensation is a forced change in exposure relative to the value determined by the exposure meter. Positive exposure compensation causes the camera to increase the exposure by a specified amount, and negative exposure causes it to decrease. For example, if the camera’s exposure meter allows one step overexposure under certain conditions, you should apply an exposure correction of – 1 EV to get a normally exposed frame.
The modes determine the exposure
Most cameras offer the user four standard exposure detection modes:
P – program line Mode (Program auto). The camera itself determines the optimal (from its point of view) shutter speed and aperture values. If you are not satisfied with the proposed expopair, you can move the program by selecting a different combination of shutter speed and aperture that provides the same exposure. The law of interchangeability in action! You can reduce or increase the exposure by using the exposure correction (+/ -). P is the optimal mode for a novice photographer. I use the program mode myself when I have to shoot in a hurry and I don’t have time to think about small things like shutter speed or aperture.
A (Av) – aperture priority or Aperture value. You set the desired aperture value, and the camera determines the appropriate shutter speed. Exposure compensation only affects the shutter speed, but does not change the aperture value. Aperture priority mode is my favorite mode. For me, it is very important to have constant control over the aperture in the first place, to control the depth of the sharply depicted space.
S (Tv) – shutter Priority (Shutter priority or Time value). The opposite is true – you set the shutter speed, and the camera selects the aperture. This mode is less flexible than the previous one, since the aperture range is always narrower than the shutter speed range. Shutter priority can be very useful when shooting moving objects.
M-Manual mode. Here you are in full control of the situation, setting both the shutter speed and the aperture at your own request. The camera’s exposure meter in this case only suggests the correct exposure, but does not impose it on the photographer. This mode is especially useful for Studio shooting, when the lighting does not change from one shot to another, you are not in a hurry and you need very precise control over the exposure. When working with Studio flashes, the M mode is simply irreplaceable.
Numerous scene modes (portrait, landscape, sport, macro, etc.), as well as the fully automatic AUTO mode are just variations on the theme of P, A or S with a heavily reduced functionality. Leave them for beginners. If you are reading this article, it means that you are able to master the traditional four modes of exposure detection.
The methods of metering
The methods of metering
Depending on your preferences the camera’s exposure meter can use one of three ways to measure exposure:
Matrix (Evaluative) metering evaluates the light the whole frame, takes into account the contrast level and offers a well-balanced exposure. I use matrix metering almost always. If the exposure doesn’t suit me, I apply exposure correction (exposure compensation) and get what I need.
The center-weighted exposamer also collects information from the entire frame, but when calculating the exposure, priority is given to the Central section, which can be useful if you want to expose the frame primarily on the object, ignoring the background. I never use this method myself, but it’s a matter of taste.
The spot metering device takes into account the illumination of only a small point in the center of the frame. This can be useful for high-precision exposure detection, but only if three conditions are met: first, you must have enough time, second, you must have a good understanding of the Zone system, and third, the very process of exposure measurement must be interesting to you, since the practical benefits are questionable. For film, this method is justified – you can’t see the picture you just took on the screen and get into the correct exposure the first time, but when shooting with a digital camera, using a matrix exposamera paired with exposure correction allows you to work much more quickly.