Kenneth Waller <[EMAIL PROTECTED]> wrote: >>If it proceeds to chuck away information after getting that instruction, >it is not a clever file format for photographic use > >Mike, jpeg, by definition is a compression program. No matter what the >setting, when utilized, it will by definition toss out some info.
Furthermore, JPEG is not a bitmapped image format: It works by transforming an image into its amplitude and frequency components. When an image is transformed into the frequency domain, it's relatively easy to progressively throw away information starting with unnoticeable data and proceeding to gross loss of image quality, depending the amount of image compression desired and quality required. But a JPEG image must be rendered in bitmapped form to be displayed on a computer monitor. And after being opened it's stored (and manipulated by Photoshop) in memory in bitmapped form. If this bitmapped version in memory is changed in any way it obviously has to be transformed back into the frequency domain again in order to be saved as a JPEG, so every time you open a JPEG file and change it in any way it will go through the JPEG conversion process (which is slightly lossy, even at maximum quality settings) again. This also applies if you open a file, make no changes and do a "save as". -- Mark Roberts Photography and writing www.robertstech.com
