Purpose of recessed lens board on Toyo/Omega 4x5 Cameras?

[harlequin]

Hello Team,

Was out with a some friends shooting and noticed on Omega E camera he was using recessed lens board, shooting
With 90mm wideangle lens....the other party was using 75mm wideangle lens on sinar f, but on a flat board?

A) is it because the design of the camera that the omega needs lens closer to ground Glass?
B) does a recessed board affect the image quality?
C) naturally this observation came to me an hour after everybody left? Must be the curfew....

Appreciate your feedback on this, I just don’t understand why one can use flat lensboard and the other recessed?

Many Thanks!
Be Safe!

Harlequin

 

[Ian C]

A. Recessed lens boards allow placing the lens at the correct distance from the film to attain focus on cameras that require such a board. This is due to the physical limits of the design of the camera. On some cameras, a flat board might work, but might requie the bellows to be nearly compressed. That’s not good for the bellows. It also makcs movements difficult or impossible.

A recessed board can provide a more-relaxed bellows position. We might also employ a short bellows or “bag bellows” as well to aid getting the lens at he proper distance from the film and to make movements easier. Which to use is dictated by the design of the particular camera.

B. The type of lens board in use is irrelevant to image quality.

 

[John Koehrer]

What he said^^^^^
FWIW: It's pretty likely that your friend using the 90 wouldn't be able to focus on infinity with the 75.
The Sinar's a bit more flexible that way

 

[juan]

There is also a recessed lens board adapter for Toyo/Omega that allows use of 4x4 lens boards. It allowed swapping lenses from say a Speed Graphic with the 45E. Without looking closely, it looks just like the regular recessed lens board.