What if enlarger lens not exactly in line with uppers?

[jay moussy]

Making a DIY lens board for a vintage condenser head enlarger, here.
I find my shop skills rusty, and cannot be sure that my lens placement is dead center - very close, but no way to tell beyond that.

Will it matter if the lens is not quite in line with the condenser set above?
What would be the telltale sign?

 

[Bikerider]

Probably very little difference where the condensers are concerned, but the panel that holds the lens MUST be 100% in alignment with that of the negative carrier. If it isn't and the lens is used wide open of close to it, there is a danger that part of the negative will be out of focus unless stopped down.

 

[jay moussy]

Probably very little difference where the condensers are concerned, but the panel that holds the lens MUST be 100% in alignment with that of the negative carrier. If it isn't and the lens is used wide open of close to it, there is a danger that part of the negative will be out of focus unless stopped down.

If your concern is lens and film being on parallel planes, I have that, as board rests on a aluminum casting that is mechanically connected to film holding plane.

 

[ic-racer]

Corners may not be in good focus if it is not centered due to most lenses having somewhat curved focal plane and or image resolution falloff at the very corners that may be difficult to detect at first.

 

[Bill Burk]

Just hold the lens in your hands and move it around to see what happens.

I did this with a simple lens and the projected image of a light bulb skewed and spread badly unless I aimed it right.

You may get pretty good with your home built board, but you can tell what to look out for by just playing around a bit.

 

[Doremus Scudder]

... I find my shop skills rusty, and cannot be sure that my lens placement is dead center - very close, but no way to tell beyond that. ...

If your lensboard is square or rectangular, check center using diagonals from opposing corners. Measurements from the corners to the mounting hole should be equal. If the board is round, just measure from outside to the edge of the hole; measurements should be the same all around.

You don't need accuracy to the thousandth of an inch either. If you're really worried you might be a bit off-center, use a longer-focal-length lens than the usual "normal" focal length for your format (e.g., 100mm instead of 80mm for 6x6). That will minimize the possible effects from mounting the lens slightly off-center.

I imagine that if you eyeball your lensboard and can't see that the hole is off-center that you'll be fine. The eye is a more precise instrument than people often think.

Doremus

 

[jay moussy]

Uh.. geometry eyeballed to best of my ability, I had to resort to using a glue gun to attach the threaded mount ring to the board!
I did not have a suitable screw style around (size, head size).

To be finished with mounting and dry-test tomorrow!