Half a breath

The standard instructions for having a chest X-ray taken are to take a full breath and hold it, then press yourself against the X-ray plate and stand still. When I first got one taken, both the first and second attempts were unusable. An expert (there are geniuses in every field, as Richard Feynman says) was called in, who glanced at the film and told me "Only take half a breath." Apparently my lungs when fully inflated are larger than the standard chest X-ray plate!