I think the focal length proportionality goes more according to the diagonal dimension of the film than the area. Area is kind of a second degree function because it's film format length X width. a 45mm normal for 35mm film pretty much corresponds to about an 80mm for 2 1/4 and about 160mm for 4x5. Otherwise we'd have 180mm normal lenses for 2 1/4 and 800mm normal lenses for 4x5. Have I completely confused you yet? That is my specialty:) ----- Original Message ----- From: "Jim Brick" <jim@xxxxxxxxx> To: <pure-silver@xxxxxxxxxxxxx> Sent: Friday, October 29, 2004 5:48 PM Subject: [pure-silver] Re: Depth of Field (35mm vs. 4x5 or 8x10) > At 04:36 PM 10/29/2004, Gene Johnson wrote: > > > >1600mm? You sure about that Jim? I was thinking more like 400. He used a > >100mm on his 35mm camera > > > The 4x5 frame is roughly 16x the 35mm frame. This is all about image > magnification. 16x 100 = 1600. > > But I could be wrong and would gladly accept another proof. > > Jim > > ============================================================================ ================================= > To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there. > ============================================================================================================= To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.