With film photography, ISO was the indication of how sensitive a film was to light. If you remember going to buy film, you had your choice of different sensitivities. There was one for shooting outdoors (100), one for indoors (400), one that was indoor/outdoor (200), and one for shooting in low light (800). The lower the number was the lower the sensitivity of the film was and the finer the grain was in your photograph.
In Digital Photography, ISO is the measured sensitivity of the image sensor, just like film sensitivity. So the same principles apply as in film photography. The lower the ISO number the less sensitive your camera is to light and the finer the grain.
In Digital Photography, an ISO of 100 is generally accepted as ‘normal’ and will give you crisp shots with minimal noise or grain. However, each camera manufacturer actually has a native ISO setting that produces the best quality exposure. One way to find your native ISO is to set up your camera and take multiple shots; with each shot only change your ISO level, and then compare your images.
Digital cameras have an auto ISO setting, this feature allows the camera to calculate the scene and make the best decision for what the camera thinks will produce the best exposure. This is a great feature if you are just documenting what is going on in a scene. However the feature will hinder you if you are trying to be creative. The second downfall to the “Auto” setting is it can easily be tricked, this usually happens when you have a scene with very strong contrast between highlighted areas and shadows.
Almost all cameras, including camera phones, will allow you to select your own ISO setting. This is helpful and most effective when you want to use different aperture and shutter speed settings to create your photographs. Taking the controls over also allows for more creativity in your photographs and gives you a wider range of subjects to shoot. For example, say you wanted to photograph a moving car, or a bird flying. The ISO only judges the light; it does not take into account what the subject is or is doing. So the auto setting will give its best guess on how much light should be in the scene. By having control over the settings, you can do multiple things with your image…here are a few examples and explanations.
What to think about
When choosing the ISO setting there are a few things to take into consideration:
- Lighting – Is the subject well lit in the scene or is there little light?
- How do I want the light to affect the overall image?
- Grain – Do I want a grainy shot to give an aged look or one without noise?
- Stability – Is a tripod needed?
- Subject – Is my subject moving or stationary?
- How fast is the subject moving?
- How would you like the movement to be displayed?
If there is plenty of light, the subject is stationary, and you want crisp image with very little grain keep your ISO low. However, if it’s dark or the subject is moving at a fairly rapid rate, consider increasing the ISO so a faster shutter speed can be used. ISO is an important aspect of digital photography and exposure. Take your time exploring the setting so you can gain more control of your digital camera and your creativity.
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