Why do you have to put the shades in a airplane up during take off and landing?

It's also so you can see outside the window if there is a crash. There might be fire or debris blocking one of the exits and you need to be able to see this before you try to get out through that exit. Plus if it is much lighter or darker outside than in the plane, your eyes need to adjust before you can see where you are going, and even though it only takes a couple of seconds, you might not have much time. Having your eyes already used to the outside lighting will make getting out in an emergency a little bit faster and in an emergency, even a couple of seconds makes a big difference.

Sorry I don't have a definite answer but I am curious to see if someone else does. I always assumed that they made us do that on landing so the flight attendants would have less work neatening up the plane for the next flight.

(yikes, I just read the other answers and I was wayoiff. Guess I won't take it so lightly next time they ask me to raise the shutter)

i flew on us airways and there was nothing like that at all, the only requirement we had was to be seated at certain times and have a seat belt fastened at certain times. i watched outside as we took off and landed and the kids loved it, it was really interesting. we even flew passed a lightning storm with the shades up, it was really awesome...we saw the clouds actually hit together and it made the whole sky light up. I'm sure we were miles from the storm, but it looked like we could reach out and touch it.

Most crashes occur at that time. If the are shades are up, it's easier to see if the lights fail. Also, a fly-by jet can see in and make sure everyone is OK if there is a hijack warning. If the shades are closed when they are supposed to be up, you can assume there is trouble inside.

Yes it's to allow light in from outside if the internal lights fail.

cordial is talking bullshit.

Letting in the ambient lighting outside will allow your eyes to adjust just incase of an emergency

This should be specific to your country. In Europe there is no such thing.