Thank you for this link Bruce. It had the following formulae A=2arctan(d/2f)
and a table informs us that a lense of 180mm will have an angle of view of 13.7degrees.
Yep I am thinking of 120 film Helen but on a 6x24 fotoman.
It just stuck me as odd that most of the manufacturers, even on a 6x17, go from the 90/5.6 Angluon XL on to the 180/5.6 Symmar L an switch from a 110 angle to a 75, missing out the 110 & 150 Super Symmar XL and the only thing I can think of is that the latter are twice as expensive, and as you rightly say Claire the XL range has a larger image circle for the same focal length, giving much greater movement and probably a much less noticeable fall of in light. And since fotoman are putting bellows, as an option, on their panoramics I may well need it.
O, and by the by Helen your photos may be quirky at times e.g. the Tissue box covers, but they are definetly not snaps.
Thanks all