Long Lenses Etc

I have a 9.5 inch Gold Dot Dagor in an Ilex that I'm running on an Ansco

5x7. I'm told it will cover an 8x10 OK (does this sound right?). I'm

looking for either a good 21" Dagor (will this cover an 8x10 when I

upgrade?) or some or other triple convertable lens. Can I get by with a

barrel shutter? And just what is a barrel shutter? How good are these

convertable lenses, and are they at all easy to come by? (I've been

haphazardly looking for a 21" for a couple of years; I've never come

across one in Toronto (I live near there), I came across a 19" in

Chicago, I expect I'll have to go to New York to get the 21". Any

suggestions? I had read somewhere that Andreas Fenninger built himself a

really long lens -- have you ever come across any literature on this

subject?

If you are not tied into older lenses specifically, try wht Nikon has. Possibly the newer Schneiders. Pricey, but excellent quality. Also Ron Wisner has a series of lenses out. I don't know much about them, but if Ron is having them made they are probably good.`