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Learn Photography

Beecher's Handouts >

9 – ISO


Again, the sensitivity of the sensor to light is called ISO.

ISO is the International Organization for Standardization.

They set standards for companies to follow.

Low ISO Settings

A smaller ISO value, say 100 or 200, means the sensor is less sensitive to light.

You need lots of light to use a low ISO.

However, the quality of the photograph is better.

High ISO Settings

Higher ISO values, such as 400, 800, 1600, are increasingly more sensitive to light.

Higher ISO values enable you to photograph with less light.

But, the quality decreases as the sensitivity increases, due to noise.

Auto ISO

Auto ISO is the default setting on your camera.

It will change the ISO value automatically depending on the intensity of the light in the scene.

If you prefer to change the ISO yourself, use the values below.

Typical ISO Values

Light Intensity

ISO Values


50, 100, 200

Shade, overcast



800, 1600, 3200


Noise in digital photography corresponds roughly to grain in film.

There are two types of noise:

1) Specs of anomalous colors (color noise).

They're often magenta (pink) and green.

2) Specs that are brighter or darker than they should be (luminosity noise).

They look grainy.

Noise is most visible in areas of a photograph that have a similar color or tone, such as shadows.

Noise Examples

The photograph immediately below was taken at an ISO setting of 200.

The lower photograph was taken at an ISO setting of 1600.

You can see degradation in the color in the bottom photograph.


ISO 200


ISO 1600

In the enlargements below, you can better see this deterioration in color fidelity.

You can also see the increase of noise, most easily seen in the shadow area and background.


ISO 200


ISO 1600

Reasons to Use

Different ISO Values


Use Lower ISO

Use Higher ISO

Not enough light


Need to use a faster shutter speed, such as when using a zoom lens at 300mm


Want highest quality blacks, such as when doing night photography


Want the best color  
Want less noise