How cold is too cold for your digital SLRs? Living in the Midwest, it gets rather cold here, so I'm a bit concerned about still being able to take pics when the weather gets bitter. I have a Canon Rebel XT, and all they say in the manual is to put it in a plastic bag when you bring it back in from the cold until it adjusts to the warmth, in order to prevent condensation. What is the coldest temperatures you'll go out with your digital SLR? Are the mirrors or lenses in any danger of freezing over in winter weather? Do you actually use the plastic bag trick? Do you have any other cold-weather tips or tricks you use? Thanks in advance!