From what I've seen of TK-42 footage eg Alic Cooper on Tubeworks 1971
http://www.youtube.com/watch?v=QRHFIVJtqpc and Johnny Winter on Tubeworks 1970
http://www.youtube.com/watch?v=-SeLISb0xyg , having an image orthicon tube as the luminance channel you get lots of haloing on the highlighting like you would on a standard B&W IO camera, apparently TK-42s were deemed as inferior to the TK-41 due to jerky zooming and grainy pictures and a few other design flaws which is why NBC hung onto their 41s till the 44s came in. From those 2 examples of TK-42 footage it looks like the 42s gave TK-44 style pastel pictures with TK-41 style purple halos on the highlights.