Understanding The exposure triangle : Aperture, Shutter Speed and ISO

In the earlier post we discussed in brief the very basics of photography to give an outlook about what creates an image you click. In this post we will try to understand more deeply about those factors- The exposure triangle (Aperture, Shutter Speed and ISO).

Before moving on to next levels, perfection on basics is essential. So after having a rough idea about the three pillars a deeper insight will make things more clear.

We can say that ; in photography, what measuring is to a tailor, Exposure plays the same for a photographer. It’s the backbone of photography.Understanding the whole exposure triangle and how it works is one of the basic steps to start with.



  • Every image require a suitable setting and location. In portrait style, a larger opening of he camera lens is required so that it focus more on the foreground and makes the background blurred.
  • Plus make sure you focus properly so that you get a proper aligned focus.
  • For which aperture’s fstop value f/2.8 or f/5.6 is recommended.
  • Besides Aperture, focal length and distance from the object also matter in depth of field.
  • Lens of focal length 200-300mm should be used not a wide angle lens like that of 25mm. As a wide angle lens will focus on overall image.
  • For making the background blur, minimise the distance from the subject which can be done by using the longest lens one possess.

    Landscape / Street Photography

  • Here a wide angle lens with small aperture opening such as f/16 is recommended.
  • It will provide you better shots keeping everything in focus and giving you a crisp sharp image with highlighting small details.
  • A wide angle lens maybe of 21mm or 55mm is recommended which will take everything in focus for a winning shot.

Shutter speed

  • Controls not only the amount of light entering the lens but also the duration of the light into the lens.
  • When hand held, in case of long lens the shutter speed should be much faster than a short lens.
  • The background shake more with the shaking handss, with longer lens shutter speed should be set much faster so that the shaking is reduced as compared to short wide angled lens.
  • So rule of thumb is shutter speed should be equal or more than he length of the lens.
  • For example, for a 21mm lens the shutter speed should be 1/30th of a sec and for 135mm the shutter speed should be of 1/200th of a sec.

Eliminate all camera movements by a tripod while focsuing on shutter speed.

Hand held


  • As we have discussed earlier ISO is the amount of sensitiveness of lens to light.
  • In case of low light use high ISO, above 400.
  • In low light your main concern should be ISO as exposure will mainly depend upon the light that is entering the lens.
  • Aperture and shutter speed will be metered by camera itself. (Why is it so ? Read in the next point)
ISO 200 ( 100 is best for daylight)

The Exposure Triangle

  • After getting some points clear abourt the main aspects, now we can understand how to use them.
  • The triangle works interdepending on all the three factors.
  • These days cameras come with metering.
  • In which we change the fstop value of aperture than we have to change either of the two (shutter speed or ISO) accordingly, third one is adjusted automatically.
  • For example-
    1. if you are shooting with an aperture of f/16 then the suitable shutter speed would be 1/30 and ISO around 200.
    2. When the aperture is f/8 then the shutter speed has to be increased from 1/30 to 1/250 and the iso value increases automatically from 200 to 400.
    3. Similarly when the aperture is f/4,  then the shutter speed has to be increased from 1/250 to 1/500 and the iso value decreases automatically from 400 to 200.
exposure triangle
the triangle


So notably we can say-

  1. ISO 100: – with slow speed – Use for daylight, bright sun, beach. snow
  2. ISO 200: – wih slow speed – Best for overcast days and in the shade
  3. ISO 400: – with fast speed – Good for sports photography and rainy days
  4. ISO 800 :- with high speed – Used in low light, evenings, sunset, indoors with a flash

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