tilting a lens

[Kurt M.]

Hi
I am curious in trying to use an enlarging lens to take photographs (I am trying to build my own tilt/shift contraption for this).
I am wondering if I have to make sure that the axis of rotation for the tilt movement has to go through the center of the lens, or if this does not matter?
thanks in advance

Kurt

[Bill L.]

My camera has base tilts (as opposed to axis tilts) on both front and rear. You have to refocus after tilting, since the lens to film plane distance changes when you tilt either side, but I don't find this to be a problem. I think it tends to be personal preference - I use a field camera, and the other advantages outweighed the loss of axis tilts.

Cheers!
Bill

[Kurt M.]

thanks Bill
certainly good to know! I was trying to remember the optics part in physics... (not much help I'm afraid)...

[Len Middleton]

Kurt,

As well as the re-focus that Bill mentioned, you might need to re-compose as a non-axis tilt could cause the ground glass image may shift.

Also depending upon your camera to subject distance, you may need to watch the coverage of the lens at the longer distances (i.e. closer to infinity).

Good luck with it,

Len

[Leonard Evens]

For a theoretical lens, if you tilt about an axis not through the center of the lens, you sshift the center of perspective of the image. This will affect both focusing and what is in the frame. But in practice, it is easy enough to compensate by focusing and using a rise or fall. My camera has base tilt, and I've never had much trouble with this,

For a real, as opposed to a theoretical lens, it gets more complicated, and it is hard to design a mechanism which will insure absolutely no change of the above kind. ( Even cameras with axial tilt will produce some shift. ) Some cameras, such as the Arca Swiss may be purchased with such mechanisims, but it doesn't seem worth the cost to me.

[ic-racer]

Building your own camera and using a barrel lens will present you with many, many more things with which to worry about. Tilting through the lens axis would be way down on the list. :)