Category Archives: English

Things to take care when buying a used Lens

Ever considered buying some second hand camera lens? twiching.com has written a post for the non expert.

Know what you’re after. Do a bit of research on the lens you want. Classifieds, eBay, etc will give you an idea of the price, and camera forums will give you an idea of common problems to check for with specific models. Both of those are probably more useful than most of the stuff below.

With that in mind, here’s some general steps for checking out a lens…

Read more on twiching.com

LA Youth Hack Jam

Want to Teach Kids to Code? Send ‘Em to a ‘Hack Jam’
100 Kids and their adults gathered last weekend in Los Angeles to learn how to program, how to think, and how to start making things. This is what happened and why.

Enhanced by Zemanta

Elapsed time in UNIX shell

The other day I had enough calculating the time so I just wrote this script:
cat > ~/bin/timediff
#!/bin/sh
if [ -z $2 ]; then
echo "usage: $0 "
echo
echo "ex. $0 11:49 12:51"
exit 1
fi

end=`date +%s -d"$2"`
start=`date +%s -d"$1"`

diff=$(($end-$start))

diff=$(($diff/60))
hours=$(($diff/60))
min=$(($diff%60))
# Prepend a 0 if minute <10
if [ ${#min} -eq 1 ]; then
min=0$min
fi

echo "$hours:$min"

Of course, it works in some cases only. This one is fine:
$ sh ~/bin/timediff 11:49 12:51
1:02

Whereas this one will not work:
$ sh ~/bin/timediff 11:49 1:51
-9:-58

But the output is quite obvious.