Hi - I'm new to DV and have an XL1s - I've been looking up accessories and have been looking into the wide angle lens - but I was told that I would need a matte box to go with it?

Can anyone tell me why a matte box is necessary and what it does?

A matte box is a device which holds mattes and filters in front of a lens. A matte is a cut-out shape which you shoot through. A common one is the old double-circle "binoculars" matte from countless war movies of the '50's and '60's.

You do not need a matte box to go with a wide angle lens, but you should be careful to block any extraneous light from directly entering the lens.

Thank you Chris

Do you know which one is a good matte box for the XL-1 ? I saw they are all quite expensive (and i really don't know why, because technically it is only something made out of light metal, not very complicated). Do you know if the 3/3 or 4/4 works together with the filters of the Cokin P series ?

Matte box machining actually has to be quite precise in order to securely hold the filters, and in some cases one or more of the filter stages can be rotated, all of which adds to the cost of trhe box.

At this time I have no specific brand or model to recommend. 3x3 filters will work with the XL1 but you're pushing it... 3 inches is 80mm and the XL1 lens diameter is 72mm. I think 4x4 filters would be a better choice.