Bellows extension Question, 300mm lens with 5x7 format

[dimento]

I'm trying to get an 8x10 kit together and in the interest of economizing on lens selection, I was considering using my schneider 300mm lens with 5x7 and 8x10.

They will be separate cameras and the 5x7 camera has a rail length of 52cm, will this be sufficent for half length and head and shoulders portraits with the 300mm on 5x7?

I guess I could look for a longer rail if needs be, but I'm not sure the bellows would stretch. Is there a formula or something to work this out. I don't have the 5x7 camera to hand, otherwise I'd just check it

thanks

D

[chris_4622]

D

I don't know the math but I use a 300mm on my 5x7 for this type of work and never get out to 52cm of extension for head and shoulders compositions.

[Ken Lee]

See http://www.kenleegallery.com/html/tech/bellows.php

If your camera can extend to 450mm, then it can make a 1:2 magnification with a 300mm lens.

For 5x7 film, a subject at 50% magnification will be 10x14 inches. That's head and shoulders.

(450-300) / 300 = 150/300 = 1/2 or 1:2

[mdarnton]

50cm of extension, film to lens, on my camera gives about a 18x28cm field. Remember that film to lens distance will always be somewhat short of rail length.

[dimento]

great stuff guys thanks, a mine of information as usual, cheers, Damian