I have a few questions about these lenses compared to regular El Nikkor lenses in regards to B&W printing. I am getting a new to me used enlarger (4x5) and am printing from mostly 6x6, 6x7 and 6x9 negatives. (rarely 35mm) What would be the advantage in the above APO lenses compared to lenses I have now (50, 80 and 105 El Nikkor enlarging lenses)? Can you use the Schneider 90mm lenses for 6x9? Is the performance similar between the APO Schneider 90 and the APO Rodagon 105. I've been told the APO Schneider 90 is a better performer but can it still be used for 6x9 negatives effectively? I would be purchasing either new if needed.