I've been asked to take pictures of our town's outdoor Christmas in the Park event, particularly of the main attraction which is the lighting of the town's name and logo in candles. They will light the logo up in candles and want pictures of this, which they will use for the town's Christmas/winter cards and for other publications. Tripod, obviously. How much would I have to up the ISO? I really don't want it to turn out too grainy but worry about the result if I don't turn it up enough. The candles arrangement will be done out in a big field and on snow, so that will give a little bit of reflective light. No flash I'm sure, that would just ruin the effect. Any insight is greatly appreciated!