Understanding F Stops, Aperture, Shutter Speed and ISO

This is the second of the series of posts by Mili Sharma on the technicalities of photography. 

game of light

Photography is nothing but a game of light. If you understand the light and you know how to play with it, then congratulations! You are a photographer!

Light keeps on changing depending upon various factors like weather conditions, structural design, locations etc. This is where “Aperture” comes into picture. This is a mechanism by which we can control the amount of light required for clicking photos according to various light conditions. Aperture is nothing but the size of the hole from where the light enters into your Digital Camera. It refers to the diameter of the hole. The more the diameter is, the more light will enter into your Camera sensor.

Now let us understand what an F-Stop is. It is also referred to as focal ratio, f-ratio, or relative aperture. It is the ratio of the focal length of the lens and the diameter of the hole from where the light enters the camera.

F stops

The common F Stop numbers are:

1.4   2   2.8   4   5.6   8   11   16   22

A trick to remember this series is that just memorize 1 and 1.4 and then start multiplying it by 2 in this way –


F Stop 1.4 would be the biggest opening whereas F Stop of 22 would be the smallest opening in the camera lens.

Another important term to know is the Shutter Speed. Shutter speed is the duration for which the shutter is open to expose light into the Camera sensor. It is measured in fractions of a second. Slow shutter speeds allow more light into the camera sensor. Slow shutter speed is used in low light conditions. Shutter Speed is inversely proportional to the Aperture. Examples of shutter speed are 1/2, 1/4, 1/8, 1/15 etc.

Once you understand the F Stop, Aperture and Shutter, you should know how sensitive your camera is to the available light.  This is measured by a term called ISO. If the ISO number is low, you Camera would be less sensitive to the light whereas if the ISO is high your camera would be more sensitive to the light. When ISO is doubled, the exposure is also doubled. This means that the ISO and Shutter Speed are proportional to each another. Low ISO is used for low image noise. Examples of ISO are 100, 200, 400, 800, 1600 etc.

I hope this would have helped you understand your Digital Camera well. Happy Clicking!!

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