Camera Exposure

A very important part of photography is the concept of exposure. Exposure is a term used to describe how bright or dark an image is. Exposure is controlled by three different parameters on a camera. If you use your camera in an automatic or preset mode, all these things are controlled automatically by the camera. In order to access this control for yourself, you need to put your camera into manual mode. Most cameras, even point and shoot ones, have a manual mode, so you don’t need to spend thousands of dollars to experiment with exposure.

Shutter Speed

The first major control of exposure is the shutter speed. This controls how long the shutter opens to let light hit the sensor. typically, this can easily range from 1/4 second to 1/1000 of a second on point and shoot cameras to around 30 seconds and 1/4000 of a second on SLR’s. Sometimes they could be even more on specialized cameras. Shutter speed controls the exposure because it controls how much time light has to hit the sensor. The longer time, the brighter the image. The shorter the time, the darker the image. Shutter speed can be used creatively to create very interesting photos. One example is light painting. The images below are pictures created by using light (like a laser or a flashlight) to draw on a surface during a long exposure time of  a camera. When the picture is taken, it appears that light has been “painted” in mid-air.

Image by Taylor Pemberton

Image by Lichtfaktor


You can also use shutter speed in the opposite direction. You can capture fast-moving objects or people and essentially stop them mid-motion using a very fast shutter speed. The image below shows a waterfall taken with multiple different shutter speeds.


In photographs, the camera shutter speed can h...

Image via Wikipedia

By Gregory F. Maxwell


The next control used in determining exposure is called lens aperture or f/stop. Inside a camera lens, there is a kind of shutter that widens or narrows the diameter of the light allowed to enter the camera. The f/stop controls how wide or narrow the diameter is. I’ll go into more detail on how aperture works and how to use it artistically in another post. For now, all we need to know is that the larger the f/stop number, the LESS light is allowed to enter. The smaller the number, the MORE light is allowed to enter.


Finally, the last control is called ISO. ISO stands for International Organization for Standardization. Why does the S come before the O? No one knows. Basically, ISO is a standardized way of measuring the sensitivity of a camera’s sensor. So instead of controlling how much light is coming in, ISO controls how much the sensor is affected by light. High ISO numbers increase the sensitivity, while low ISO numbers decrease the sensitivity. The downside of using ISO to brighten an image up is that your images begin to have more pronounced image noise. Image noise is grain or spots that show up in images because of inaccuracies within the camera’s sensor. noise shows up more when you use high ISO values because increasing the sensitivity of the camera to light, increases the sensitivity to noise as well. This is especially seen in point and shoot cameras which already have problems with noise even with low ISO numbers. It does also apply SLR’s however. SLR’s can have much higher ISO numbers without having too much noise, which allows them to be able to take pictures of dark areas much better than point and shoot cameras. In short, no matter what camera you have, it is good to keep your ISO as low as possible while still being able to maintain correct exposure.

Learning about the technical aspects of cameras is important if want to create quality photos. But even more important than learning is doing. Now that you’ve been given an introduction of the basics of camera exposure, go experiment and have fun!

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