It wouldn't hurt to fill-out custom's forms in advance of your trip.
Information from these USA forms can be photocopied by Canadian officials at the boarder.
Most photo equipment has serial numbers...include all of these #'s on the declaration forms.
This will save you paying duty on items you already own...in both directions, coming and going.

Marc

Certificate of Registration For Personal Effects Taken Abroad

http://forms.cbp.gov/pdf/cbp_form_4457.pdf