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ISO is the digital camera equivalent of ASA in film cameras. When buying film, you would choose the ASA based on what you were taking pictures of. Now on a digital camera you just adjust the ISO setting. Here are the different settings and what they're used for:
High ASA film would use larger crystals of light=sensitive chemicals. They would capture more of the available light, allowing you to shoot in low light situations. I tried ASA 1000 film several times. It would, for example, let you take a photo of people sitting around a campfire in the dead of night, but use the illumination from the fire to light up the faces. The trade-off was that the larger crystals made the photos noticeably grainy. High ISO settings are accomplished in a digital camera by increasing the amplification of the electrical charge coming from the sensor as light hits it. Here the trade-off is that higher amplification introduces 'noise' into the signal, making the image lose contrast and appear blurry. High ISO values are extremely useful for making your photos brighter in low light areas, and will also let you increase the shutter speed; I used it a lot when shooting indoor sports. What you choose for the ISO will depend on what you're using the photos for. You can set it quite high if you're making small digital images for the web. However , quality printed enlargements may show blurriness if you set it too high. How high you can set the ISO without noticeable image degradation is almost exclusively a function of how expensive your camera is. Incidentally, the danger in letting your camera set the ISO for you, which inexpensive cameras do automatically without letting you change it, is that they prioritize brightness regardless of the image quality. You may see a nice bright image on your camera or phone, but it will be noticeably degraded when you see it on your computer screen. |