What the heck is a "rebuffal"?? Gosh, Ian, where have you been for the last half century, ever since optical multicoating began? My comments were
about polyester filters. Acrylic resin filters are something completely different, but nonetheless easily marred, electrostatic (attract dust like all acrylics), and prone to secondary reflections. ... In other words, not ideal outside a studio environment. Gel filters are downright fragile, expensive,
and not optically equal to better modern glass ones. I don't care what source you quote from 1942 concerning them allegedly having no effect on the
image. There are better choices these days, unless you need a very special type not available in glass. These were made for various scientific and
technical lab application, not just conventional photography, so the choice at one time was impressive. I can still remember unpacking my Sinar up
on the windy end of Titcomb Basin in the Wind River range a number of years ago. The sun was setting. Another guy showed up with a Tachihara
4x5, with seven lenses in his pack, and then started fooling around with a stack of about twenty Wratten gels. Most of them were messed up with
grit and creases - inevitable in that environment. I had plenty of time to notice what he was doing, cause I had taken my shot and was all packed up
again while he was still fooling around. The sun set before he got a chance to do anything. Gels filters flapping in the wind, granite sand flying around
his little stack of them on a rock, trying to keep one or two of them actually flat in a gel holder under those conditions. Gosh, even the wretched
Tiffen sandwich-style glass filters I owned back then were dramatically better.