to look for a commercial 300mm as it has been reccommended by several people. However, I am told that from 10" to 14" are good in different ways.
I would like to do portrait and full figure in a studio setting.
What do you have and use?

Can the 300mm be used in landscape setting..or for taking buildings etc?
I already have a 210mm lens which I am told I can use for outdoor photographs with
the 8 x 10 back.

I find the advice of people who have used different lenses etc. is more helpful than finding and reading a book.
Your advice appreciated. )