What is ISO

In Photography a term ISO generally came across with context to senstivity of image sensor or film to light.Lower the number the less sensitive your camera is to light and finer the grain.Higher ISO settings are generally used in darker situations.

ISO is measured in numbers: 100,200,400,800,1000,1600,2000,6400 etc depanding upon camera manufacturer settings.

Changing the Aperture affects the depth of field while changing the Shutter speed affects freezing or blurring of motion.And changing the ISO numbers affects the picture quality.Higher the ISO,more grainer the picture will look.Lower the ISO lower the grainy image will look.



                                                           Above picture showing as we shift to higher ISO number, more grainy the image will be.

Whenever choosing for ISO, one must keep in mind these 3 things:

  1. Availabilty of Light : While choosing ISO it is necessary to asess the availability of light.Suppose you are shooting Indoor where there is only available tungston light or dim light,e.g you are shooting in a ambient light at birthday party,where lighting concept is dim light in banquet hall then you have to raise your ISO to higher numbers to get the actual feel of the lighting setup inside.On the other hand if you are shooting a landscape in daylight then you have lower down the ISO to ‘say’ 100.That will give you more crisp images.
  2. Subject Movment: If you are trying to shoot moving subject in low or dim light,then you have to choose high ISO.Very big reason for this is that you can’t slow down your shutter speed.To freeze the motion you will choose higher ISO instead of slow shutter speed.
  3. Noise:ISO is the term which is directly related to the Noise.Hope you must saw somewhere the images having grains over it.That is just because when we choose higher ISO somewhere in low lighting situations.If you want grainy images then you will have to choose higher ISO or vice-versa.


Now a days full frame cameras like Canon Mark III,1Dx Mark II  are producing stunning picture quality even at Higher ISO.