ISO can be an intimidating feature but it doesn’t have to be. In this tutorial we will unmask the ISO feature.
First things first, ISO stands for “International Organization Standardization”. Now I’m not going to go in depth about the acronym of ISO. Not because it’s not important because it is. It’s just boring. I only bring it up because it’s one of the first questions you get about ISO. So there it is. If you feel compelled to learn more about International Organization Standardization, Google it.
So let’s jump right in. The ISO setting tells your camera how sensitive to light it needs to be. The lower the ISO, the less sensitive your camera will be to light and the higher the ISO, the more sensitive it will be to light. The spread of ISO setting for most cameras is 100-1600. However, many D-SLR’s now (and over ambitious point and shoot cameras) are going to 3200 and even 6400 ISO.
As a general rule, you want to use the lower ISO settings when possible. At this point, very high ISO settings, although cool, are a bit unrealistic in practice because too much noise is processed into the image. On the other hand, too low of a setting (depending on your shutter) can process an image that’s too dark. Remember, you don’t always have the luxury of using a tripod, controlling the light source and asking everyone to stay perfectly still. This is where It gets a little tricky so here are a few sample pictures to help out.
The Image to the left was a jpeg taken using a Canon EOS 40D with an ISO of 3200, 1/25 Exposure and an F/4 aperture. The main light source was a large window about 10 feet to the right with the blinds half closed. It was also a cloudy day so the room was fairly dark. Also let’s imagine I could not use a tripod, flash or change the lighting. I did this to illustrate a what a difficult lighting situation might look like. For example, this is sometimes the case in a church or museum. Now if you click on the Image you will get the Higher resolution version of this picture and you will see how much noise was processed into the image, definitely too much noise for a Coke bottle and a plant. However, what if this was a family member doing something extraordinary or an item at a museum and you forgot your tripod (not that you would want to lug one around a museum anyway). Sometimes noise can be acceptible if it means capturing the moment. We don’t always look at our pictures for critical analysis.
Here is an image of the same subject taken at 500 ISO with all other setting were the same. If I wanted to use this ISO setting, I would have had to slow the shutter considerably. Remember to imagine I can’t use a tripod. Check the image below to see what full auto with no flash looks like. The camera chose a shutter of 1.3” seconds and I could not hold the camera still enough to keep the image sharp. This is one of the key principles around ISO. If you can sacrifice a bit of noise you can get a much faster shutter and help eliminate image blur ether from your self or someone you’re taking a picture of. On a side note, image stabilization can help but it can only help so much and if its your subject that is moving it does nothing.
So thats it for now, go out and try different settings your camera has and see what you get. Remember It does take some trial and error. Have fun.
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