WELLOG                                 DISPLAY RESOLUTION

 

Revised 5-22-2008

© 2007-2008 WELLOG

All Rights Reserved

 

COMPUTER DISPLAYS:

 

Computer displays use picture elements referred to as “Pixels” to form characters and images. Each horizontal and vertical line is divided into picture elements. All computer displays have a specified number of pixels. Common specifications in terms of horizontal and vertical pixels are 640x480 (VGA), 800x600, 1024x768.

 

 

Note: it is an unavoidable fact that a digital computer display will show a stair step behavior when showing a straight line drawn at an angle.

 

 

RESOLUTION:

 

The resolution of a computer display is equal to the number of pixels available for display purposes. Therefore, the more pixels used in a display, the better the resolution.

 

View an example of a line drawn at 45 degrees on a strip chart – evaluate your display.

 

 

COLOR:

 

Computers use a digital representation for color display.

 

Basic 16 color displays a created using one of 16 possible colors.

 

True color is represented using 24 bits and can generate 16,777,216 different colors.

 

Color resolution is based in the number of bits used for generation of color.

 

LIMITATION OF DISPLAY:

 

The pixel resolution of the display limits the amount of data that can be graphically represented. If a computer display is used for presentation of waveforms that have greater resolution than the display, then the number of data must be reduced by compressed to fit within the limited resolution of the display. Data acquisition systems may have a resolution of 12 bits which provides 4096 possibilities of data representing voltage levels. If a display is used that has a vertical resolution of 768 pixels vertical resolution, then the display can only represent 768 possible voltage levels. In order to accommodate 4096 voltage levels, the 4096 voltage levels must be reduced to 768 pixels. One process used is to divide 4096 by 768 = 5.333 voltages per pixel. In order for the waveform to be fully displayed on the computer, 6 voltage levels are averaged and the required pixel is selected to represent the average of those 6 voltages. The signal may then be presented on the display using 683 pixels. If a smaller portion of the available display is used, then fewer pixels are available to represent the number of possible voltage levels. For example, if 100 pixels are used, then 41 voltage levels are averaged and the appropriate pixel is selected for each of the 100 averages of voltages.