There was a time when I took a lot of photos. A common comment in photo mags was to put a plain glass filter over the expensive glassware to protect it. I also had a desire for undistorted images. That led me to set a tripod at the front door and a large gridded target at the fireplace. I had a shifting lens that I could rotate through 180 deg and a 2x extender made for short lenses. This gave me a 70mm side looking lens that would copy onto slide film the same detail visible to the eye at the camera location.
I was hunting big game. I had spotted a new Ontario Northland 50-foot boxcar in dark blue and the yellow zig-zags, without a spot of dust or dirt on it, up in Baltimore set out next to a little-traveled public street. I went to the tripod, slipped my gridded focusing screen in, and tested for pincushioning in both directions followed by a check that the detents to flop 180-deg to look sideways the other way was exactly in the same plane. To Baltimore! Kodak made two 10 x 7.5" color print enlargements for splicing. I think they were very close to being exactly O-scale (each technician used his own magnification for "8x10 full frame", but the Kodak color fidelity was always impressive).
The moral here is, if you want undistorted results, don't put anything thicker than a gel film filter in the lens' light path. Then only if you have to. So, having spent $25 on this TV camera, cut the molded plastic insert out of the window. Wasn't that intended to diffuse light, not transmit it? 
--Frank
PS-- Camera should be able to see signals if towed behind TMCC F3 that uses postwar-dimensioned shells and has a trailing cab (F3A) unit. In rare instances, a train could have a caboose on both ends.
