Espon V750-M Pro Scanner

[neil poulsen]

That is the posterisation I referred to. You mention doing it at the scanner, but with most scanners, you are not doing it "at the scanner". Most edits during the scan process are to data that has already been scanned, and it does not make a difference if you do it immediatley after the scan (as in the scanner sw) or later (in PS). Hence, it should make no difference. This is assuming that you are working at the same bit-depth.

Steve

This has been my contention, that (most) prosumer scanners inherently aren't doing anything different from Photoshop. For example, if it were possible to adjust gains, or the brightness level of the scanning light, then I could see an advantage. Or, if the scanner were collecting the data at a higher bit depth than 16, I could see an advantage. But, I've yet to hear a credible engineering argument as to why it's better to do edits at scan.

If anyone has an engineering based (how does it work) argument as to why editing at scan works better, I'd be interested in hearing it.

[Helen Bach]

Wouldn't there be some advantages if the scanner software only exported non-linear files - ie if the exported file was always a transformation of the linear data coming from the CCD/ADC? A similar argument to the one used for explaining why some adjustments are better made on a camera RAW file rather than one that has been converted to a non-linear form (for example the difference in the treatment of highlights between editing in Adobe Camera Raw and in Photoshop).

Best,
Helen

[neil poulsen]

In spite of it's deterministic nature, I can see one case where Photoshop "creates" noise. By a reasonable definition, "noise" is the difference between the actual image and what's in the data. (A computerized image is just a data file.) In the interpolation process, Photoshop models pixels that are likely different than they would have been, had the original image been captured at the desired resolution.

It's interesting. In many respects, Photoshop is a statistical engine. I wonder if there are indeed Photoshop algorithms based on random number generation.

[Kirk Keyes]

Air brush...?

[Keith S. Walklet]

A note to Bob on the diminished quality of 1800 spi vs. 1200. It is best to stay with whole derivatives of the claimed optical dpi. The 4800 dpi of the Epson is their 4800 dpi, represented by 4800 picture elements on the scanning array, which are arranged in offset rows.

Other threads go into this in more detail, but in short, 4800 spi on a drum scanner is not equivalent to 4800 spi on a flatbed, but you should notice incremental improvements in your results up to the claimed max optical resolution of the flatbed, after which you are getting interpolated data.

To scan an 8x10 at full optical resolution with a 4800 dpi flatbed will result in an impractically large file, that could only be managed with a reduction in size (see Layer Transfer Technique) that permits editing in PS.

[Greg Lockrey]

What are we saying here? Are we saying that making the scan at whatever the profile determend to be correct. Don't do anything to that file at the scanner send the file to PS and make the corrections there, the file will be the same as if I made my corrections first? I must be missing something, I don't see this to be the case. Why are the histograms broken if I do my corrections in PS and not when done at the scanner?

[Steve Kefford]

In spite of it's deterministic nature, I can see one case where Photoshop "creates" noise. By a reasonable definition, "noise" is the difference between the actual image and what's in the data. (A computerized image is just a data file.) In the interpolation process, Photoshop models pixels that are likely different than they would have been, had the original image been captured at the desired resolution.....

Obviously the definition of what noise is is important when discussing it. I don't understand your definition because, as you suggest, the image is the data. Besides, noise is a fairly standard concept.

A definition from Wikipedia "Image noise is a random, usually unwanted, fluctuation of pixel values in an image. Image noise can originate in film grain, or in electronic noise in the input device (scanner or digital camera) sensor and circuitry, or in the unavoidable shot noise of an ideal photon detector. Image noise is most apparent in image regions with low signal level, such as shadow regions or underexposed images."

Originally, the discussion was about level/curve changes, which can not produce noise, not interpolation. However, I don't see how this could create noise either.

Steve

[David Luttmann]

Obviously the definition of what noise is is important when discussing it. I don't understand your definition because, as you suggest, the image is the data. Besides, noise is a fairly standard concept.

A definition from Wikipedia "Image noise is a random, usually unwanted, fluctuation of pixel values in an image. Image noise can originate in film grain, or in electronic noise in the input device (scanner or digital camera) sensor and circuitry, or in the unavoidable shot noise of an ideal photon detector. Image noise is most apparent in image regions with low signal level, such as shadow regions or underexposed images."

Originally, the discussion was about level/curve changes, which can not produce noise, not interpolation. However, I don't see how this could create noise either.

Steve

That's correct Steve. Adjusting curves in PS creates NO additional noise....it does however, make the noise that is in the original scan a heck of a lot more apparent by bring the junk in the shadows up into the midtones.....where they are now as plain as day.

[Steve Kefford]

... Adjusting curves in PS creates NO additional noise....it does however, make the noise that is in the original scan a heck of a lot more apparent by bring the junk in the shadows up into the midtones.....where they are now as plain as day.

Absolutley. But so does making the same adjustments with the scanner sw.

Steve

[Greg Lockrey]

Absolutley. But so does making the same adjustments with the scanner sw.

Steve

Not to be argumentative, I'm just trying to understand. If you make the adjustments at the scanner prior to the actual scanning, wouldn't this allievate the effects of noise and posterization, etc?