Last week I posted my first photography tutorial covering camera Aperture (F-stop). This week I will be taking a look at camera ISO (formerly ASA). ISO stands for International Organization for Standardization which is somewhat irrelevant for what we will be covering today. Anyway, simply put, ISO represents the camera’s sensitivity to light. A lower ISO number is less sensitive, while a higher ISO number is more sensitive. If you use your digital camera in “auto” mode, you will never need to change the ISO, as the camera does so on-the-fly as it tries to compensate for a number of variables in your shot (lighting, shutter speed, aperture, etc.). If you set your camera to “manual” mode, you gain a magnitude of power and control over your camera. For today’s experiment, I set my camera shutter speed to 1/6 and aperture to f-5.6 and adjusted the ISO after each shot.
Here you can see how the increase in ISO results in a brighter picture (ISO H1.0 = ISO 3200). So when should you use a lower ISO and a higher ISO? Lower ISO numbers between 100-320 are best used under very bright outdoor conditions. A mid-range ISO number of 400-800 is best used indoors where light is not as bright as outdoors. Usage of anything over 800 is not recommended unless absolute necessary to achieve the photograph. You see, the lower the ISO number the better quality your photo will be. Pictures with a high ISO number produce a lot of “noise”, meaning they come out very grainy.
Here is a close-up shot at ISO 800. For the most part, the photo has decent quality.
With the ISO at 3200 you can clearly see the noise in this picture.
So in closing, just remember that a lower ISO number is better for bright lighting and larger ISO numbers should be used under poor lighting conditions. Also, a lower ISO number will produce a better quality photo.