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Home scanning - yes or no?

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#26 Michal1

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Posted 25 October 2010 - 11:08 AM

I'm intrested especially in the hardware controls. These software things can be always made in a normal image processing software if the scan is in the 16-bit format, can't they? The only contribution of the scanner's internal software is you needn't to do the same operation for every photo individually. I'd like to verify, that the getting of a 16-bit unadjusted scan from a photo lab is equivalent to a scan made at home.

#27 Dave Kodama

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Posted 25 October 2010 - 11:12 AM

Michal,

There are no hardware controls on any scanner I've used. At least there are no physical knobs to turn. Presumably, the software provided by the manufacturer is actually controlling some hardware internally when you adjust the software exposure, gamma, etc.

Dave

#28 Rick Thurmond

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Posted 25 October 2010 - 10:13 PM

I think an important adjustment that can best be done in the scanning software is the selection of black point and white point. SilverFast allows that, and I'd imagine that on at least some scanners, it adjusts the hardware.

In SilverFast, you can take a prescan, then have the software show a histogram. If you adjust the black point to just below the darkest data, and set the white point just above the brightest data, then it will spread the range of density values on the film across the range of pixel values. If it does that by adjusting the hardware, it can do a better job than doing the same thing in Photoshop.

I typically make a liberal adjustment in the scanner software, then fine tune it later in Photoshop using the levels tool or for more control the curves tool.
Rick

#29 Michal1

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Posted 05 December 2010 - 08:09 AM

I wanted to make sure whether those speckles in the scan I posted above are film grains or scanner noise. I took an image of the film using a microscope and LPI webcam. Here is the comparison of the scanned and micro image (star Xi Cyg). The first frame is 52x34 pixel (0.50x0.32mm) cut from 3543x2516px Cygnus image above. It can be seen the grain size is comparable with the size of pixels in the scanned image. It seems the dark speckles in the scan could be caused by the film grain. The LPI image was calibrated for dark and flat field. The small dark rings in the micro image seems to be diffraction rings incurred by particles of dust on the film or some pimples on it.


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