Sam's Photography Tips

ISO

What is ISO

ISO in basic terms describes how sensitive your camera is to the available light. A lower ISO value makes the camera less sensitive to light, while a higher ISO value make it more sensitive to light. The image sensor is a component within your camera that can change its sensitivity, its job is to collect and process the light into an image. Increased sensitivity allows your camera to capture images in low light without a flash, the downside to a higher ISO is that it adds grain or ‘noise’ to your image.

Cameras have a base ISO this is a value that will produce the highest quality image it can with adding noise or grain to the image. Camera usually start with ISO 100 and increment in powers of two, for example the first four values would be 100, 200, 400, 800. ISO 400 is twice as sensitive to light that ISO 200 and four times more sensitive than ISO 100. It is best to stick to a low ISO number as this will produce the best results but sometime we may need to use higher values in the case of low light conditions.


ISO and Shutter Speed

ISO Number Shutter Speed
ISO 100 1 second
ISO 200 1/2 second
ISO 400 1/4 second
ISO 800 1/8 second
ISO 1600 1/16 second
ISO 3200 1/32 second

Using the table above, if your camera needed one second to take a photo at ISO 100, then changing the ISO value to 400 will allow you to capture the same image at ¼th second or 250 milliseconds.


Using ISO

You should always aim to stick with the base ISO of your camera, use a low ISO value when there is a good amount of light available as this will retain the most detail and produce the highest photo quality. A low ISO can be used in low light situations but the camera should be mounted onto a tripod or placed on a stable platform. You will also most likely need to adjust the shutter speed to a lower value as this will allow more light to hit the sensor, this is sometimes referred to long exposure.


When to use a higher ISO

You may need to increase your ISO value if you need to capture an image quickly but the light level is too low. When increasing the ISO, you need to ask yourself if you think its ok to add noise to the image.

The two images below show how changing the ISO can effect your image. The image of the left was taken using an ISO value of 100, when taking photos you should try to stick to this number as it produces the best quality images. The image on the right however was taken using an ISO of 6400, if you compare it to the other image you will notice it contains some noise.

ISO Example 1
ISO Example 2