This is the same question I have been struggling with myself, and did not find it answered here in the forums or in the large format lens primer... so please excuse me resurrecting this old thread and I appreciate your help in trying to understand!
What I am concerned about is the "crop factor" of e.g. a 150mm lens with an image circle for 8x10 being used on a 4x5 back. Is this now essentially a 300mm lens focal length perspective on the 4x5 back/camera? (Similar to this unanswered photo.net question: 8x10 lens on 4x5 camera)
I have an 8x10 camera with 4x5 back, and plan to mostly shoot 4x5 but want my lenses to cover 8x10 as well. I just found the 8x10 lens list (which details the image circles ~320mm+) and the 4x5 lens list. Now my concern is that since the image circle of a 150mm lens for 8x10 (e.g. Nikon Nikkor SW 150mm f/8 -- has 400mm image circle) is nearly 2x larger than the 150mm lens for 4x5 (e.g. Nikon Nikkor W 150 f/5.6 -- has 210mm image circle)... I tend to believe there is also a 2x crop factor of the "8x10 lens" when used on a "4x5 camera" (same as swapping out the 8x10 back for a 4x5 back)?
So for 4x5 normal perspective (shooting 4x5 back on 8x10 camera), if I bought the 'wrong' 150mm lens (Nikkor SW instead for 8x10)... I presume I would effectively be shooting 300mm since I'm cropped in on the 150mm image circle for 8x10?
Bookmarks