ISO Sensitivity in Photography
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In tradition film photography, ISO sensitivity is a measure of how sensitive the film is to light. Film with lower ISO rating requires longer exposure (e.g. leaving the shutter open longer) and is also known as slow film. Vice-versa, film with higher ISO rating requires shorter exposure and is known as fast film.
But digital photography doesn’t use film, you say? That’s right but ISO sensitivity still plays a big role. In the digital world, ISO measures the sensitivity of the image sensor to light. The higher the ISO setting, the more sensitive the sensor is to light and vice-versa. ISO settings will appear as ISO 100, ISO 200 up to ISO 3200 and above.
However, as with film photography, the higher the ISO, the more visible grains will appear in your images. The grains that appears is also known as noise.
When to use which ISO Settings?
Most modern digital cameras are equipped with Auto ISO setting which will adjust the ISO according to the lighting conditions. This function is great, most of the time. Occasionally, the Auto ISO setting will not be able to choose the right settings. It is important to know when to use which settings so that you can select the right settings when Auto ISO is not giving satisfactory results.
In a bright and well lit environment, as a general rule, try to use the lowest ISO setting as possible. Most cameras can go down to ISO 100. This will make your images appear tack sharp and crisp. Low ISO settings will only work if you’re in a well lit environment. Low ISO does not work well in badly lit and low light conditions (e.g. Indoors, Night time etc.)
For dark or indoor environments, it is slightly more complicated. You have several options:
- Turn up the ISO to make the sensor more sensitive to light. This will allow more light into your images and make your scene appear brighter. Remember, there is a trade off for using high ISO. Grains/noise will appear in your photos making it less crisp.
- If your subject is stationary, like cityscapes, you can use a Low ISO but you will need to have a tripod to keep your camera still so that your images won’t turn out blur due to handshake.
There are times when you want the grainy effect to add more character to your images. You can also turn up the ISO setting for such circumstances.
To summarize:
Bright, outdoor environment - As low ISO as possible.
Dark, indoor environment - Use low ISO with a tripod for stationary subjects. Use high ISO for moving subjects.
Special circumstances - Use high ISO to get a grainy effect in your photos
Play with ISO, aperture and shutter speed to experiment and get a better feel of what each setting does for your images. Don’t forget to leave us a comment of your experiences!
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