Now by using an ordinary black and white
panchromatic film to negate our image as in Fig 5, AND switching filters,
to negate the image once more, we get a double negation, which is really
no negation at all. We get a positive color image, without bothering
with black and white reversal films. Any Black and White Panchromatic film
will do, including the old standby of "Kodak Verichrome Pan."
At the right, we have used the Green filter
for the Long Record instead of for the Short Record. Thus we need a new color
for our Short Record. In this case we have used Blue for the short record.