International Organization for Standardization: ISO

12th February 2021

A note on ISO

…One of the great advantages of digital over a film camera is the adjustable ISO – the sensitivity of the sensor or film to light. A digital camera actually only has one ‘real’ ISO, which is ISO 100. ISO values above this base setting are made possible by amplifying the signal from the camera sensor; this produces noise, the low-contrast, ‘grainy’ look clearly visible at higher ISOs…

…While it’s tempting to always rely on ISO Auto and leave ISO to float, in order to be fully aware of the limitations the available light will set on your image quality you may prefer to turn off ISO Auto for rest of this course.

OCA Expressing Your Vision course folder p.43

Below are the two pages from the Panasonic Owner’s Manual for advanced features, Digital Camera DC-GH5, which inform users about the ISO function of the LUMIX camera:

ISO is a camera setting that will brighten or darken an image. As the ISO number is increased, images will become brighter. This is useful when taking photographs in a darker environment although the higher the ISO number setting the higher noise visibility also known as grain can be seen in the image. If a lower ISO number is used then the camera is less sensitive to light and the grain within the image is finer.

As already stated in the above quote from the OCA’s course folder, ‘A digital camera actually only has one ‘real’ ISO, which is ISO 100. ISO values above this base setting are made possible by amplifying the signal from the camera sensor’ Course folder p.43

When using base ISO the images captured should be of a high quality which means the noise visibility should be minimal.

Self portrait showing noise also known as grain

However there are times when a high ISO has to be used for example when I am in a low light sport hall watching my daughter take part in Taekwondo. Using a high ISO helps me to stop unwanted motion blur so that I can obtain a frozen, sharper image of, for example, my daughter performing a kick, as well as gaining a brighter image.

Other examples I use a higher ISO for are:

  • If I need grain for aesthetic or conceptual reasons
  • Indoor shoots for example concerts, galleries and museum visits
  • When I am not allowed to use flash
  • When photographing movement

I alter my camera settings depending on the outcome I want for my images which includes aspects such as, Do I want a grainy image? Do I want motion blur? etc… I also take into consideration the available light and if I have my tripod or camera bean bag with me.

Planning for the above criteria informs my decision making to which ISO setting I would use. However, there is such a large variation in ISO numbers on the digital camera that I know that I do not have full control over my decision because I am not aware how each one will alter the final visual outcome of my image. In the ‘good old’ days when using 35mm film, the choices were very limited and I mostly used ASA (American Standards Association) 100, 400 and 800.


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