Increase of space angle with angular radius
[ICO]NameLast modifiedSizeDescription

[PARENTDIR]Parent Directory  -  
[   ]illumin_cz.gnp2014-07-04 18:59 1.2K 
[   ]illuminanceP.gnp2014-06-25 19:07 1.6K 
[   ]illuminance.gnp2013-05-06 13:30 1.5K 
[   ]illumin_cz.pdf2013-02-08 11:15 8.1K 
[   ]illuminance.pdf2012-11-27 19:58 11K 
[IMG]illuminance.png2012-06-18 22:48 7.9K 
[IMG]space_a15dg2.png2006-11-27 18:49 9.9K 
[IMG]space_a15dg.png2006-11-27 18:49 9.5K 
[IMG]space_a15.png2006-11-27 18:49 9.9K 
[   ]space_ang15.gnp2006-11-27 18:49 1.5K 
[IMG]space_a30dg2.png2006-01-04 11:03 10K 
[IMG]space_a30dg.png2006-01-04 11:03 10K 
[IMG]space_a30.png2006-01-04 11:03 10K 
[IMG]space_an_dg2.png2006-01-04 11:03 11K 
[IMG]space_angle.png2006-01-04 11:03 11K 
[IMG]space_an_dg.png2006-01-04 11:03 11K 
[   ]space_angle.gnp2006-01-04 11:00 1.5K 
[   ]space_ang30.gnp2006-01-04 11:00 1.5K 

Increase of space angle with angular radius is shown with various horizontal and vertical scales: radians or degrees, steradians or square degrees.

It is amazing, how well a planar approximation of pi*r^2 works... The graphs going just to 30 degrees radius show, that up to 15 degrees, even cosine correction (giving illuminance of a plane) is completely negligible.

*.gnp are programs which have produced the resulting *.png by a command like
gnuplot space_angle.gnp
– it's easy to adapt them to produce scalable PostScript output instead.

(made by Jan Hollan, subject to GNU public license)