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Flatbed Scanning Hints

MIDDLE TONES AND GAMMA

  
Gamma primarily adjusts the Midtones, and leaves the end points alone.

Normal Gamma Curve
Normal Middletone area, Gamma 1.00

If a scanned picture appears too dark (common when colour pictures are converted to B&W greyscale), do not use the brightening options to fix the problem as this will simply lighten the picture range but not improve picture-detail contrast.

All scanning software should come with the option to alter the gamma of the scanned Image, and studying the 3 pictures on this page will show how gamma adjustment works. The small 'o' spots the Middletone value.

Consider not only the two faces but also the graduation beneath them. Altering the gamma does not effect the blackest Shadows or the whitest Highlights, but pushes the Midtones (areas around the middle of the Greyscale) higher giving us an apparent darker picture or lower giving us an apparent lighter picture.

In the area at the top right hand corner of the images are the letters AVR. By using Gamma to move the midtones you either increase the quarter-tone detail contrast and flatten the three-quarter-tone detail contrast, or vice-versa. This result can be seen slightly with the AVR lettering. Once understood, the gamma control can be used to enhance light cloud detail in skies or enhance the subtle detail in the dark areas in and under trees etc..

Note: If a picture requires the use of the Brightness control and/or the Contrast control, then adjust these first before altering the gamma.

Bright Gamma Curve
Middletone area Gamma 0.50

Dark Gamma Curve
Middletone area, Gamma 2.00

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e-mail 1997 '98. Last Revised:  Friday, 31 October 2003 22:04