Although Retinex automatic image enhancement featured in PhotoFlair® works on any digitized image, it gives the best results with original uncompressed digital images: i.e., uncompressed images acquired directly from a digital camera, frame grabber, or slide/negative scanner.
A. Compressed Images
Compressed images (e.g., JPEG format) often have, so called, compression artifacts in them. The extent of the compression artifacts depend on the degree of compression and the sophistication of compression algorithm. Sometimes, when enhancing a compressed image using Retinex, these artifacts also get enhanced and become visible. This can be avoided by using Retinex on uncompressed images (e.g., TIFF format), where available.
B. Scanned Images
Images that have been scanned from photograph prints can be enhanced so that the scanned image looks close to the original photograph but details in shadows are lost, making enhancement of dark areas difficult.
Retinex works better on images digitized by scanning negatives rather than prints. Negatives retain the dynamic range of the original scene at least an order of magnitude better than prints. Thus they retain the color information that allows the Retinex to perform better. Scanned negatives from a flatbed scanner provide better digitized images than prints scanned on a flatbed scanner; however, best digitized images are obtained by scanning negatives on specialized negative scanners.
C. Old Photo Restoration
The Retinex process works particularly well for restoring images obtained from scanning faded photographs (see example below).
If you have old pictures that you would like to enhance, then your best bet is to scan the negatives rather than the printed photographs. Click here to see more examples
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