Integrated Circuits
CMOS
TTL
A to D
D to A
Voltage Refs
CMOS Switches

Microprocessor
Microchip
Atmel
Programmers
Crystals
Boards and Jigs

Sensors
Light to Freq
Color
Photomultipliers
Barometry

Test Equipment
DVM's
Calibrators
Tek Plug-Ins
Audio Analyzers
Signal Generators

Masking a photographic negative is done for several reasons. First, a mask can be used to alter the contrast of a negative.  By controlling the degree to which contrast is altered subtle highlights or shadow detail can be brought out in a way that would otherwise take hours of painstaking burning and dodging.  The second reason for masking, unsharp masking, is that an image's apparent sharpness can be enhanced by building up the contrast around edges. 

	To the left is a scan of a Stauffer Graphic Arts 4*5 step wedge.  Each step represents a 0.15 change in density
	The image on the left is a mask of the Step Wedge above, Ilford Lith Film taken at f/16 with a 135mm lens at 21 inches. The film was developed in Dektol 1:10  for 4 minutes.  The denisty range of this mask is about 0.37
	The image is a mask, same exposure, developed in Dektol 1:10 for 8 minutes. The density range of the mask is about 0.75