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31. PIXELS and RESOLUTION

The word "pixel" has come up over and over again in the preceding lessons as a way to measure widths and heights. Today's lesson discusses pixels and a related concept, resolution.

You'll need a RULER for today's lesson!

INDEX CARD #31:

PIXELS AND RESOLUTION (31a)

What is a "pixel"? "Pixel" is short for PICture ELement; a pixel is a single point in a graphic image. Graphics monitors divide the screen into rows and columns of pixels: for example, the author's laptop monitor is 1024×768, which means that 1024 pixels can be displayed across each row, and 768 pixels can be displayed in each column.

What is "resolution"? "Resolution," in general, refers to the sharpness and clarity of an image. Resolution is measured in different ways for different devices.

"Monitor resolution" is measured by stating the number of pixels on the screen. For example, the author's laptop monitor has a resolution of 1024×768. The higher the resolution, the more detail can be rendered on the screen.

Printer resolution is often measured in units of "dots per inch" (dpi). For example, a 300 dpi printer is capable of printing 300 dots in a line 1 inch long.

LENGTHS MEASURED IN PIXELS (31b)

Will a 100 pixel line look the same on everyone's monitor? Absolutely not! Its length will be determined by both the resolution of your monitor and the width of your monitor. Consider the 100-pixel line below:

On the author's monitor, it is 1.1 inches (about 2.8 cm).
On my daughter's machine, it is 1.9 inches (about 4.8 cm).
How long is it on your machine? (Measure it with a ruler.)
Let's see why this line is 1.1 inches long on my monitor:

The screen area on my monitor is 11.2 inches wide (I measured it).
I know that my monitor is 1024 pixels wide.
Therefore, there are 1024 pixels per 11.2 inches.
If there are 1024 pixels in 11.2 inches, then there are 100 pixels in 1.1 inches. How did I get this? Click here to find out! Due to the web's current inadequacy in displaying mathematics, you'll need Adobe Acrobat Reader, which you can download free at: http://www.adobe.com/products/acrobat/readstep2.html

Printable version of Index Card 31a

Printable version of Index Card 31b

WORKSHEET #31:

(W31.1) If necessary, download Adobe Acrobat Reader, and view the explanation on card 31b.
(W31.2) Then, solve this problem: Bob's screen area is 17 inches across. His monitor resolution is 800×600. How long will the 100-pixel line appear on his machine? (SOLUTION)

ASSIGNMENT #31:

(A31.1) Please read pages 14–16 in the Weasel Book (up to "Monitor Color Issues").