Camera ISO: a brief description

Camera ISO: a brief description

ISO is one of the three pillars of photography, along with aperture and Shutter speed.

If you understand how these three work together you have total control over your camera and anything is achievable. This is what turns an amateur photographer’s work  into professional looking images.

What is ISO?

The sensor in your camera captures the light which enters through your lens. The sensors sensitivity to that light determines if your image will be too bright or too dark. You can tell the sensor how sensitive it will be for the photo by using a low ISO figure if the light source is bright and a high ISO if the light source is dark.

Digital Camera ISO

At ISO 200 the image is exposed correctly at ISO 1000 it is overexposed

In the image above the section of the image on the left ISO 200  is exposed correctly, by making the ISO bigger the image gets brighter and is overexposed. You strive most of the time, in photography to replicate the images exposure to the exposure of what your eyes see.

Origins of ISO

The first inventors of photography found that different chemicals mixed together was light sensitive. When placed on grains silver halide and exposed to light ,the exposed areas burnt to black and the dark areas remained white. This created a negative image of what the camera’s lens was looking at. Reverse the dark areas to bright and the bright to dark and the image the camera captured was replicated in black and white. The stronger the mix of chemicals the more sensitive the silver halide became to light so increased sensitivity ISO had an important role in photography from then on. With increased ISO photographers could take photos in doors and in low lighting.


When sensitivity is increased so also does the chances of your image becoming grainy (when you look closely at the image you can see the dots clearly which make up the image). This is caused because the ISO is too high for your cameras sensor. The cameras sensor is the most expensive part of your camera, the more money you spend on a camera the better the sensor is able to  function with high ISO. Have you ever taken a photo with a camera phone and you were so pleased with it that you wanted to print it at maybe 10″ x 8″, but when the size of the image was increased the image was all grainy and no good. Camera phones have small cheap sensors which means the quality of the image blown up will be terrible. Maybe one day camera phones will have a large sensor but this will be reflected in the price also.

Digital Camera High ISO

“Night time prayers” High ISO was used taking this low lit image