size+and+download+times

I do a unit on "essential image information for the www" (year 10)

I talk about image formats (bmp, jpeg, gif, png, xcf, psd), file sizes (images tend to be larger), the difference b/w a byte, KB, MB, GB, TB etc., the importance of compression, download times (6 KB/sec for 56K modem), that people don't like waiting - Jacob Nielsen studies show more than 10 seconds is intolerable, etc.

I have a worksheet about all of this

I try to make it concrete - for example I get students to convert a bmp (260 KB) to a gif (6 KB) and then a JPEG (20 KB) and then calculate download times for each file over a 56K modem bmp 43 secs gif 1 sec jpeg 3 secs

It's hard work teaching this - there is a lot of learning involved here

some brief points:


 * by default Windows XP now conceals the 3 letter file endings, so that's another thing to teach - how to not hide them
 * many students can't do maths, can't convert KM to MB, don't realise you have to divide by 6 to calculate download times etc.
 * a lot of students in disadvantaged schools such as my schools don't have computers and / or internet at home
 * some who had internet lose it because they haven't kept their virus protection, firewall and updates in place
 * the significance of different image formats is new to most - some are native formats (xcf, psd), some are old (bmp), some are compressed (gif, jpeg), some are new and not used as much (png)

I'm just trying to teach the essentials but it sometimes feels like I'm not making a lot of progress