Hi Merlin66
1988 it started with the TV 4" f5 Genesis with a Petzval design (optical).
1992 came the Genesis-sdf Pentzval design with a fluorite corrector lens
1995 the TV-101 was born
2001 came finally the NP-101 this time Al Nagler modifies the Petzval design
http://www.televue.com/engine/page.asp?ID=191
I have never seen one of those bad read a lot about them because at one stage I wanted to buy a Genesis-sdf.
To make a long story short, the NP-101 is the only true APO. The TV-101 is good for photography (with film) but visually not that well colour corrected. The Genesis-sdf is slightly worse especially visually. The older Genesis is rather pure corrected by today’s standard and can be compared to a F8 Achromatic lens.
Because of that I never bought the Genesis-sdf nor the TV-101 (and I can not afford the NP-101).
If you read between the lines of the tests you come to the same conclusion.
http://www.cloudynights.com/item.php?item_id=940
http://www.cloudynights.com/item.php?item_id=934
http://www.cloudynights.com/item.php...1141&pr=2x6x15
http://www.cloudynights.com/item.php...=707&pr=2x6x15
http://www.cloudynights.com/item.php...=970&pr=2x6x15