Thanks for the input, now I know what to look for. I have been offered a Emil Busch Comb 36" II lens. I have no idea if it will cover that format. The guy selling has no experience with lenses (he sell antiques). I has no lensboard and is very cheap. I am thinking about using it on my 12x16" camera too. I guess it will cover that format without any problems.
If a man does not keep in step with his fellows it may be because he hears a different drummer... Thoreau
In the modern era the best buys would be process lenses in the 30-35" range. Any lens of this type (Apo-Tessars, Apo-Nikkors, Red Dota Artars, etc.) will cover 20X24 easily. For super modern types, the 600mm Fujinon A would be a great lens, and the best of all is the 550 XXL Schenider, which is really a multi-coated Dagor type lens, and super contrasty. But you will have to pay a lot for the 600mm Fujinon-A and the 550 XXL.
Any Dagor of 19" or more should cover 20X24 with movements, but these also tend to cost a lot.
I reckon that my 600m f/9 apo-rodagon process lens should cover 20x24 with some movement. The thing just weighs so much, I think you can forget putting it on a wooden camera. I did take it past 1:1 with a ridiculous piece of aluminum extrusion as a rail, but you know what my problem was? Couldn't reach all the way from the darkslide to the lens to hand shutter it. :rolleyes: Now that is a problem, when you need an assistant just to pull a darkslide.
Besides all these glorious oldies, what about pinhole Should be quite special at that size.