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Old 05-02-2008, 8:30 PM
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Arrow ISO Noise

ISO Noise

ISO stands for International Organization for Standardization but I've more commonly heard it called International Standards Organization. It refers to the sensitivity of camera film or a digital camera's sensor and is sometimes called "speed". The higher the ISO "speed" the more sensitive to light the film or digital camera sensor is, resulting in brighter photos. The lower the ISO, the lower the sensitivity is and the darker the images will be. I guess the
International Standards Organization does a lot of things, so why in the world this particular camera setting is called "ISO" is beyond me. Personally I would have simply called it brightness.

There is one big drawback with using too high of an ISO setting. It results in photos that have a grainy appearance like they have sand in them or like an old TV set getting a weak signal. This is referred to as noise, and the higher you set the ISO, the more noise you'll have in the photos. The first 2 images below were taken with an ISO of 80 and the next 2 photos were taken with an ISO of 800. (For some reason the Canon A710 IS camera doesn't seem to be saving the ISO setting in the EXIF data, so you'll just have to take my word for it. )









Clearly, the last 2 photos (with the much higher ISO of 800) are inferior in quality. Grainy noisy photos are a common thing I see in the forum once in a while (especially with cell phone camera shots - another reason to avoid cell phone cameras! ), so I thought I'd mention it here. ISO noise becomes less noticeable when the photo is resized to a smaller percentage, but it can still cause photos not to look as sharp and crisp as they would with a lower ISO.



If using the camera's auto mode, the camera might choose a high ISO in low-lighting conditions which will cause this graininess, so the more ambient lighting ( "ambient" = the normal light in the room/environment), the better. Any extra lamps, worklights, lanterns etc. that can be setup and used will help cause the camera to choose a lower ISO when in auto mode so that the photos won't be as noisy. This explains why people using auto mode on their cameras (or other auto settings on the dial such as "Portrait", "Landscape", or "Fireworks") sometimes get nasty grainy photos. Then again, there's plenty of times where with good lighting the auto mode works great and there's lots of nice shots on the forum to prove it.

Really, the best thing to do (in my opinion) is to shoot in full manual mode and use a tripod. This allows you to manually choose the ISO setting yourself so that it won't be too high and thus you won't get those sandy-looking photos of your scanners. With a tripod, you're free to use a slower shutter speed without camera shake blur, so that the picture won't come out too dark.

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Camera Settings Are About Tradeoffs

Now that you know a bit about the 3 main camera settings that make up the exposure (shutter speed, aperture, & ISO), you can see with a little bit of trial and error in full manual mode how you must compensate for changing one setting, by having to then change another setting. Increasing the shutter speed makes for a less blurry photo when shooting handheld, but it also makes the picture come out darker. To then compensate for this and make the picture brighter, you could increase the ISO, but that might make for a noisier photo, -OR- you could open up the aperture (choose a lower f-number) to let in more light, but that may cause some objects at different distances not to appear in focus. Then again, if the lighting is too low to begin with, a faster shutter speed could cause the photo to come out completely black altogether so that you have no choice but to accept a little bit of blurriness due to camera shake.

It's all about tradeoffs and making decisions depending on what you're shooting, because there's a limit to how far the camera settings can be adjusted in any direction. You could literally be up until MIDNIGHT trying all the different combinations of settings. Even attaining an exposure value (EV) of a perfect -0- on the camera's exposure meter on the LCD display could still render an underexposed photo ("underexposed" = too dark) if the scanner is black in color or the desk has a dark wood color.


Thank God for auto mode!


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