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ISO/Film Speed and Noise

February 2, 2010 Comments off

ISO/Film Speed (100, 200, 400) and Noise

***Most Digital cameras will only allow you to change your ISO if you are in full Manual mode. You camera may allow you to set an ISO range while shooting in Automatic mode, and adjust your shutter and aperture for you depending on what ISO it determines. For best results with controlling your ISO***

In film cameras it describes the films sensitivity to light.

The lower the ISO (100) the more light it needs for correct exposure.

The higher the ISO (1600) the less light it needs for a correct expore.

In digital cameras the concept is the same except that you replace the film with the camera sensor.

The lower the ISO (100) the more light the camera sensor needs to correctly expose a photograph.

The highter the ISO (1600) the less light the camera sensor needs to correctly expose a photograph.

ISO can determine your image quality. ISO in a digital camera will control the amount of noise you see in your image.

Noise

Your digital camera uses a sensor instead of film to capture the light. What your camera’s sensor will do is if you are shooting at night with a high ISO and a fast shutter speed your camera will take that small amount of light and amplify it. Because your camera’s sensor is less accurate the less light it receives it will randomly generate pixels. This is more noticeable in areas of flat color and in your shadows since noise in dark areas appears as random sparkles of color.

***Noise can be used for artistic effect, but you have to have meant to do it, otherwise a photo may just look bad***

The image below was shot at ISO 100

While this image was shot at ISO1600

As you can see the image shot at ISO 100 looks cleaner.

When you are out in daylight or in a studio working with controlled lighting use the lowest ISO you can get out of your camera. ISO100 is usually a good one. The lower the ISO the less grain you will see in your photographs and the better they will look.

However, higher ISO’s are useful when you are out at night and don’t have the luxury of a setting up a tripod, like at a concert or night sporting event. Setting your ISO at its highest (ISO1600 is usually a good high ISO), will allow you to shoot at night with fast shutter speeds. This will allow you to shoot at night and still take photographs that are not just a huge motion blur mess.

As a rule of thumb

ISO100 – ISO200 for shooting outdoors in sunny conditions

ISO400 maybe ISO800 is good if you are shooting in doors or in dimmer conditions. This allows you to still take advantage of faster shutter speeds, but still get a good image quality.

ISO1600 if your lighting is very bad, as in you are shooting at night. However the higher your ISO the more noise you will see in your camera.

Just keep in mind that with a Lower ISO you will need a slower shutter speed and a wider aperture (lower f/stop number) to allow more light to get to the sensor.

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Categories: ISO/Film Speed