Originally posted by Aristophanes ultra-wide was not even very popular in film; for that you went to MF or LF.
That is rather Debatable, Hasselblad had the SWC - and many Medium format lens makers stopped at around 40-30mm mark depending on the format. With 4X5 format the widest lens* is the Schneider Kreuznach Super Angulon 47mm f/5.6 XL - which is a pretty rare beast these days. It is much easier to buy a FX format 17mm T/S lenses with less bulk and effectively the same functionality. Many of canon's lenses are from the film era the Canon EF14mm f/2.8L** being the widest for full 35mm format, and if you go back even further there was the Carl Zeiss 15mm f/8 Hologon*** for Leica M mount - focal lengths 20mm and wider weren't common but they did exist and they were generally more popular with smaller formats because of the reduced size of the lenses.
though on 8X10 format I have used a
Goertz Hypergon ****which was very interesting, but it is a
very specialised lens. With a 75mm focal length on 8X10 format it is extremely wide - consider the fact that 300mm is considered a normal lens for 8X10.
*that still allows for some camera movements.
**introduced in 1991.
*** produced in 1972-1976 - apparently only 1000 of these lenses were made, they sell for upwards of $10,000 US these days.
**** these were produced circa 1910~1920 - it is hard to pin the date of production down, but these lenses are quite rare and sell for around $3,400US