Let the picture talk...
That would only work if all the watches were the same age.It would also be nice to know the exposure settings for each shot taken, and in addition, for each watch to also be imaged at an agreed upon standard ISO, f-stop, and shutter speed so we can compare brightness between models...
Also, I'm not sure how similar various "ISO/ASA" ratings are in the digital era. In other words, I'm not sure that 200ISO on a Canon is really the same on a Nikon or Oly. The chips used vary as do receptor site size. But even among closely related cameras from the same manufacturer, the processing and firmware improvements result in dramatically different pictures at given ISOs.That would only work if all the watches were the same age.