Resolution is somewhat analogous to film grain. If you capture one image using 100 speed film and another using 1,000 speed film (Figs. 20.8a, 20.9a), you might not notice much difference until you go to enlarge the two images. Then you would see that the 1,000 speed film is much grainier (Figs. 20.8b, 20.9b).
If we take a small area of each image and enlarge it, we see that the higher-resolution image contains much greater detail. Since we have enlarged a portion of the images, we are now looking at only 238,210 and 6,324 pixels, respectively. As you can see, this difference is noticeable.
How many pixels is enough? That depends on how your images will be used. Usually two million pixels is enough for our office work. This means you can select your camera on the basis of features other than resolution. Even if you do not base your decision on resolution, you may find that the camera you end up buying just happens to have a resolution of three or four megapixels or higher. After all, the average resolution is continuing to climb. But should you always capture images at the camera's maximum resolution? Most cameras let you select from several resolution settings.
Today most cameras vary from 1.3 to ten megapixels. The key is knowing what you need from your photos. For photographs of size 8 in.x10 in. or larger, a camera with at least three megapixels is a necessity. For photograph sizes such as 3 in.x5 in. or 4 in.x6 in. you find great results and lower prices in the one to two megapixel class. It does not hurt to have more megapixels than you need, as it leaves room to grow. Just remember to shoot at a higher resolution.
Digital cameras come in all shapes and sizes. While there are some very small digital cameras on the market that produce beautiful photos, their petite size cannot physically house all the features consumers want. Keep in mind that while your neighbor has a digital camera that will fit in his pocket, your need for a x10 optical zoom or an external flash calls for an average to larger-size camera. If a small camera tops your list of important features, be aware that you may be sacrificing other features.
Now even if you do not need six million pixels you might want to have a camera that offer this. But there are higher costs of high resolution. Higher resolution leads to larger files that take up more storage space, require more RAM and may slow down many systems. Unless you have a specific reason for capturing extremely high resolution images, we recommend capturing images at a resolution of two million to three million pixels.
It does not matter how many images the camera can store because of removable storage media that allow you to transfer the images to a computer and reuse the memory card. Images are a part of the patient record. They need to be transferred to a hard drive or network server that is backed up on a regular basis.
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