Take notes so you can identify which color
filter was used to take which photograph. In fig 1, a Red filter was
used, while in fig 2, a Green filter was used. Since Red has a wavelength
of 700nm while Green has a wavelength of about 550nm, Red has the longer
wavelength. Thus the first photograph is the "Long Record".
By using a tripod and exercising care not to
jar the set up when you change filters over the camera lens, the two black
and white images should be the same,- except for the fact they both record a
different part of the scene's color spectrum.