Quote: what is the typical widest aperture on a LF lens?
Probably f/6.3 to f/8 would be typical for 10x8 format.
Yes, although for so-called 'normal' lenses - the typical plasmat designs that are used for mid-range focal lengths on most formats - f/5.6 is more common. For example, the strict 'standard' is about 300mm (as mentioned elsewhere, and the available normals in that length are generally f/5.6. I don't use 300mm, but I do have a 240mm plasmat that adequetly covers 10x8 (and is the rough equivalent of a 30mm wide angle in 35mm terms) and that is likewise an f/5.6.
However, once you get above 300mm the plasmats tend to get slower - my 360mm is an f/6.8. Similarly the wides are slower, and longer lenses are invariably even slower still - sheer size and weight considerations see to that, even if nothing else. I have a 450mm Fujinon which is a comfortable portrait length on 10x8, and that's just f/12.5. So there's quite a lot of variation, depending on the type of lens we're talking about.
But faster lenses do exist - I have (though I've never actually used it) a rather ancient f/5 12 3/4" Ilex portrait lens which easily covers 10x8, although in theory it's only intended for whole plate, which is a little smaller.
It's decidedly unusual for lenses like this to actually be used wide open though - they're generally stopped down quite a bit, and may not even cover their intended formats unless they are. Large apertures in these lenses are generally just there for easier viewing, though clearly some people do like to make use of the wafer-thin DoF and dreamy effects that are possible if you open them up.
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