Could this be used to align an enlarger?

[sk66]

I'm making an alignment cube for reproduction type work. It's a simple acrylic cube with a hole in one side and a bullseye on the other. And when the bullseye is centered in the hole the camera's optical axis is exactly perpendicular to the surface the cube is on.

I'm wondering if one could make a "calibrated negative" that would cause the enlarger to project a dot that should pass through the opening in the cube and fall on the center of the bullseye. That seems quite feasible to me, but would that then mean that the negative carrier and lens board of the enlarger are also aligned/parallel?

 

[joxby]

Can't quite get hold of this in my head.
I'm thinking the dot needs to be a laser projection and project through a hole in the cube, the smaller the hole in the cube the more accurate the alignment.
Obviously this can't really be done with a "calibrated negative" unless you can focus the dot.
Also, I don't understand the function of the bulls eye or the positioning of the cube...

 

[sk66]

Can't quite get hold of this in my head.
I'm thinking the dot needs to be a laser projection and project through a hole in the cube, the smaller the hole in the cube the more accurate the alignment.
Obviously this can't really be done with a "calibrated negative" unless you can focus the dot.
Also, I don't understand the function of the bulls eye or the positioning of the cube...

I would assume the dot could be focused; why couldn't it be (with lens installed).

The purpose of the cube is too ensure the camera sensor is exactly parallel to the recorded surface (eliminates perspective errors)... it functions in the same way the alignment sights work on the lens-align tool.

 

[joxby]

Dunno what a lens alignment tool is but I guess it does what it says on the tin.

Back to the enlarger, assuming the cube is placed on the baseboard ??
and you are trying to shoot a dot through through the top hole in the cube to project through a hole/bulls eye on the bottom of the cube on to the baseboard??
I can see how that could go a long way to highlighting errors in head/baseboard alignment.
The problem is creating the dot, I mean you're not going to be able to create this dot from anything you place in the neg carrier using light passing through an enlarger lens I wouldn't have thought, it is and enlarger after all.
By "dot" I imagine something 1mm across......holes in the cube I imagine no bigger than say 3mm.


This aside, back in my assisting day's if we didn't have the specific alignment tools for a particular enlarger, we'd place a 2ft straight edge on the negative stage and measure its ends to the baseboard at various positions with a crappy wooden ruler, did nothing for lens alignment of course but at least the board and neg stage where near enough..

 

[sk66]

Yes, the cube would be placed on the baseboard. The hole in the cube is ~ 5mm.
It would seem to me that if the projected dot was roughly the same size as the hole it would work. It's been quite a while since I've used an enlarger, but IIRC the size of the dot can be manipulated by the height of the head and the lens can then focus it on the board. Although, a greater head height will increase the accuracy of the measurement by emphasizing any misalignment.

IDK if there's really any point to it. It's just something I'm making for myself. But I've seen several enlarger alignment tools on the market which cost quite a bit. This cube can be made quite cheaply in comparison.

 

[joxby]

well, you could try a laser cut pinhole mounted on card in the neg carrier......gonna have to be perfectly flat though
I suspect a teeny pinhole at neg stage will be a 10mm blob at baseboard, but let us know how you get on..

 

[sk66]

I don't have an enlarger any more... doubt I will pursue it in that sense.

This is the cube I made (paint finally dried). It's a 2" acrylic square... I had paint bleed and the remover frosted the acrylic, so now it has frosted sides . I painted the inside of the lid white and and the outside red. Then ran the end mill cutter through the base and down to remove the white paint, leaving a red circle the same size as the hole.