Hi Dorothy
I took a peak at your site before responding, Very vice work. I think you'll have fun in 8x10.
The "classic" portrait / headshot length for 8x10 is 18 or 19 inches ( 450 - 480 mm ). The most common 19" lens, over the past 30 years, is a 19" Red Dor Artar, an american lens designed for graphic art, but having pleasant charecteristic for people ( not excessively contrasty and cruel ). It is normally used in an Ilex shutter. Faster than an f/9 lens is problematic with a moderately long lens: the only practical anser is to use a pneumatic shuuter with an air bulb, which while limited in overall range, is deadly accurate at 1/20 of a second. It is a charming way to work, as well.
If you want to play that way, you can look at the range of lovely older lenses, from Tessars to Rapid Rectilinears... and that is another question altogether. But with a studio and a business, I think your first lens ought to be in a good shutter.
Longer than 19" becomes difficult to use: the camera's extension is great, the length of your arms needs to increase to reach the front controls. Nice trick ! A 24" lens ( 600 mm) can be very useful, but more often in the studio.
Shorter than 19" is not usually helpful when you are working up close. A 14" can be excellent, but you pretty much need to keep the lens level ( unless you want to put the emphasis on the sitter's shoes !)
Now, a 19" / 480mm lens is similar in look to a 60mm lens in 35mm, if you make an 8x10 print. The depth of field you get from a 60mm at f/4 will be the same on the 480 at f/32 ( if the prints are the same size ). Most 19 / 480 lenses apertures are limited by the opening of the shutter to f/9 or 10.
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An excellent, and very classically useful, 2 lens set would be a 19" red dot artar and a 10" Kodak WF Ektar. With care, the 10" lens works well when you want to show the subject in her environment, as Adams did so well with Edward Weston and the eucalyptus tree.
