Read Sharp PG-A20X Handy Guide online
Image Measurements
Version 1.5
Issue 04/2006
Issue 04/2006
22
SHARP ELECTRONICS (UK) LTD
PROJECTOR TECHNICAL SUPPORT
TECHNICAL SERVICES GROUP
I know the diagonal screen size, how do I calculate the screen width?
Consider the following triangle in relation to your screen
The most common image format for CTV, PC and projected images is 4:3 (4 by 3). This is
also known as the image aspect ratio. This means that the height measurement is ¾ that of
the width. Using the 3-4-5 triangle rule, the diagonal measurement can be used to calculated
width.
also known as the image aspect ratio. This means that the height measurement is ¾ that of
the width. Using the 3-4-5 triangle rule, the diagonal measurement can be used to calculated
width.
Examples
Diagonal = 10m Width = (Diagonal ÷ 5) x 4 = 10 ÷ 5 x 4 = 8m
Height = 6m Width = (Height ÷ 3) x 4 = 6 ÷ 3 x 4 = 8m
Height = 6m Width = (Height ÷ 3) x 4 = 6 ÷ 3 x 4 = 8m
Although 4:3 is a popular aspect ratio there are others:
5:4
Some PCs are able to produce SXGA images, which offer a resolution of 1280 dots
horizontally by 1024 dots vertically. This aspect ratio is 5:4
Some PCs are able to produce SXGA images, which offer a resolution of 1280 dots
horizontally by 1024 dots vertically. This aspect ratio is 5:4
16:9 and 21:9
The majority of DVD format films are now mastered in Wide-Screen format, of which there are
two popular aspect ratios; 16:9 and 21:9. Sometimes these ratios are quantified with respect
to 1, so expect to see 1.85:1 and 2.35:1 respectively.
The majority of DVD format films are now mastered in Wide-Screen format, of which there are
two popular aspect ratios; 16:9 and 21:9. Sometimes these ratios are quantified with respect
to 1, so expect to see 1.85:1 and 2.35:1 respectively.
Knowing the diagonal measurement, calculating the screen width with these other ratios can
be done in a similar manner.
be done in a similar manner.
For 5:4 (1.25:1) Width = (Diagonal ÷ 6.403) x 5
For 16:9 (1.78:1)
For 16:9 (1.78:1)
Width = (Diagonal ÷ 18.358) x 16
For 21:9 (2.35:1)
Width = (Diagonal ÷ 22.847) x 21
Focal Length
This is the distance between the display panel and the focal point. The focal length is usually
printed on the lens ring and is usually preceded with a lower case f. If it is a zoom lens then
two figures will be present, one each for the maximum and minimum zoom. eg. f=32.5-44mm.
This figure can be used to calculate the image size and throw distance values if the size of
the display panel is known.
This is the distance between the display panel and the focal point. The focal length is usually
printed on the lens ring and is usually preceded with a lower case f. If it is a zoom lens then
two figures will be present, one each for the maximum and minimum zoom. eg. f=32.5-44mm.
This figure can be used to calculate the image size and throw distance values if the size of
the display panel is known.
SCREEN WIDTH
SCREEN
HEIGHT
HEIGHT
DIAGONAL
HEIGHT-WIDTH-DIAGONAL RATIO=3:4:5
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