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Tricks for Fixing Bad Images

(September 2003) posted on Thu Sep 25, 2003

Coudray describes techniques you can use to overcome resolution, color, image-quality, and file-format issues.

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By Mark A. Coudray

Problems with customer-prepared art often fall into two main categories. The first has to do with image sharpness and focus. If the problems are not too extreme, you can use Unsharp Masking, as mentioned earlier, to greatly improve those aspects of the image file. David Blatner and Bruce Fraser devote almost 100 pages to sharpening techniques in their Real World Photoshop series. The techniques for rescuing images are numerous and impressive and include dealing with film grain, facial complexions, edge sharpness, water, ice, subject textures, and many others. If you have an image you feel is too far gone, consult Real World Photoshop before you give up. You will be pleasantly surprised.


Tone and contrast are two other big problems. Images lacking in these departments look dull and lifeless because all of the values are in the same area. An example might be a lady wearing a gray coat, riding a gray horse on the beach in the fog. Not much life there! Adjusting tone and contrast can save these types of images. This is done in Photoshop under &gt;Image&gt;Adjust&gt;Curves. To add contrast to an image, you would typically apply a classic, contrast-correcting "S" curve. <B>Figure 1 </B>shows a typical curve where the highlights are lightened, the shadows darkened, and the midtones slightly lightened. This is the quickest and easiest way to dramatically improve the appearance and printability of a flat image.


JPEG file format


JPEG is a file format used to save digital photographs. It is a compression method that greatly reduces the size of the stored file. But the problem comes in the fact that JPEG is a "lossy" compression method. This means the data are lost forever when the file is compressed. The method by which JPEG works generates strange digital artifacts in the image. Artifacts typically appear as regular squares mixed into the pixels of the image. Artifacts also are highly visible along the edges of items in the image file, and often look like smoke or heat waves.


The JPEG format progressively destroys digital images. More information is lost each time an image file is opened and closed. If you were to open and close an image enough times, you would degrade the image to the point where it would no longer be useable in a commercial way.



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