[LargeFormat] Turner Reich Orange Filters

[Les Newcomer]

Clive Warren wrote:
> 

> 
> Hardly an APO lens - however apparently capable of excellent performance as
> they are a protar design with an additional element to avoid being sued I
> guess .......
> 

That's what I've heard from Ken, Don Cardwell and Kingslake. The 5
cemented elements created two problems. For  added  cemented surface,
you increased the likely hood of all elements not being concentric by at
least a magnitude. This made assembling a TR accurately painfully
difficult and I suspect quality control got a bit lax from time to time.

Second, some of the surfaces were fairly strong curve. This put greater
strain on the balsam at the edges--which is why you rarely see a perfect TR

Les