jjs wrote:
"Stephan" wrote in message
Do you check sharpness with your picture open a 100% of its size?
Well, of course. And they just suck. The scanners that we modestly incomed people can afford just suck. They ALL need a USM treatment because the ‘tween shit is just terrible.
To paraphrase young Dr. Frankenstein,
USM, USM,
There’s no escaping USM!
But, unlike the fate of Gene Wilder’s character, there’s nothing wrong with Unsharp Mask (USM). It’s a practical and mathematically valid way to make resampled images look better. Even our own eyes use a biological variation of USM to enhance edges.
Conventional printing and enlargement had similar techniques for sharpening that used optics and chemistry. For example a condenser based enlarger would print a very harsh, grainy image. A diffuser placed in the enlarger would produce a softer, but still optically sharp image. Different methods of development could enhance or reduce the contrast and apparent sharpness of the image.
The name USM came from film based photography, using a blurred negative (unsharp mask) sandwiched with the original to create sharpness. Photoshop, and other programs, have "digitized" the methods used by conventional photography.
USE FILM.
There ain’t nothin like a chrome, nothin in the world. But unless you are using conventional development all the way to the final print, and few people are these days, pretty much every pixel you capture on film will be USM’ed at almost every stage in its digital life cycle, exactly as if it were a digital image.
When negs and chromes scanned and digitally printed yes, Virginia, they are will be resampled and sharpened at some point in that process. Drum scanners, still the best scanner technology, have operator controlled USM built into the electronics that sharpens the image as it is scanned, and the Printer RIP does similar resampling and sharpening of image color values as it figures out where the final dots of color should go.
But you need not look far at all to find USM. Our eyes, in a way, defined not only the CRT’s we use to view images, but the underlying algorithms that we use to process those images for our own convenience. Our own visual apparatus uses USM-style edge enhancement to sharpen the retinal image. So, you see, resistance is futile, there is no escaping USM. —
Mike Russell
www.curvemeister.com
www.geigy.2y.net