Stops and Exposure

Do you know what are stops and exposure? Stops is a method to measure light that is allowed to pass through and exposure is how much the picture is being exposed to sunlight.

Stops is just a term mainly used in photography. It is a relative measure of light but it can’t be used to quantify light. For example we cannot say that there are 2 stops of light coming from that source. On the other hand we should say that the amount of light here is 2 stops more from another source. When one stop of light is being added, the amount of light is being doubled and is vice versa when one stop of light is being removed. For the older cameras, there is a dent in the dial so that it is easier to stop when the desired setting is reached.

You use relative measures for light because there is no real definition or standard of light. How bright a certain colour depends on how well lit is the background: a charcoal has more reflecting light when there is direct sunlight shining to it compare to when you put it in a dark pit. The important thing is not how bright your object is in that particular scene but their relative brightness to each other or in photography terms: how may stops are they apart from. The exposure setting is adjusted so that the shirt looks whiter or the charcoal looks black in sun light.

The amount of light recorded is controlled by the camera's exposure settings: ISO, shutter speed and aperture. Opening the shutter longer by a stop or opening the aperture by a stop or increasing the ISO by a stop all have the effect of doubling the brightness of your scene. Below is a general overview of ISO, shutter speed and aperture in ascending order of 1 stop:

ISO: 100, 200, 400, 800, 1600, 3200, 6400 and so on

Shutter speed: 1", 1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500 and so on

Aperture: 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 20, 32

The setting 1/125 f5.6 ISO100 is as bright as:
1/250 f4 ISO100 which is as bright as:
1/ 500 f4 ISO200

However, the shutter speed and aperture have their own special effects when being set differently. They can affect how creative a picture looks which is very hard to add or remove in Photoshop. So plan your shoot beforehand so that you can get the results that you want.

For a correctly exposed photo, the image should neither be too bright or too dark unless it was suppose to be. To get a correctly exposed photo, you must make sure that the photo is indicated by a centered meter.