8 Apr 10
Foil, mirrors and similar material fixed to card is equivalent to a spotlight - very sharp shadows, bright highlights and an excessive dynamic range for most purposes. For portraits and most group shots. a sheet is fine - just roll it up and carry it with you - it is also large enough to do the opposite task of blocking excessive light. Plain white card is fine and so is poly sheeting - just be careful that the reflected light does not convey a colour cast onto your subject. Even if it is really white (or whatever colour you choose), combined with the colour of the ambient light, it can fool your camera's white balance system.