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Based on the answers to my question Can I use a LCD as backlight for acquiring film using a DSLR? and the link provided about optimal light sources for negative film I would like to build a light source which emits no orange at all, so that the orange of the film won't be recorded by the camera.

I can find LEDs for the purpose, but they are individual light sources with various light spread curves.

How can I arrange them to build a homogeneous light box? 3D printing is possible so I don't need to be restricted to existing products.

I would intermix LEDs of the different wavelengths, but should I put sources on the side walls of a white light box which has diffusing walls and back surface? should the box be square or circular? circular may benefit from the 1/r rule and result in a more homogeneous light on the back wall/diffuser. Or should I put them not on the sides but on the back side, behind one or two diffusers? or maybe on the walls but directed to the back?

I have no experience on the topic and the goal is to obtain a uniform light field. It will be diffused light, not collimated. Collimated may be much more difficult so I can skip it for now.

Let me know if this question is more suited for engineering.SE

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Likely the best lamphouse design would be collimated light. Meaning the light rays from the light source arrive at the negative / slide as parallel rays that uniformly illuminate. The design of such a lamphouse mimics the condenser enlarger. These utilize two plano convex “condenser lenses”.

Such a design is likely best as the parallel rays deliver an image that is tack sharp and the image has high contrast.

Such a lamphouse has the undesirable trait of showing every speck of settled dust. Best is a lamphouse that suppresses dust spots.

The best design for dust suppression is a lamphouse that delivers a uniform light that is highly diffused. This will be an integrating chamber. This can be a box, or a sphere painted flat white. Light is allowed to enter the integrating chamber via holes in its walls. The light reverberates about and arrives at the negative / slide with no apparent direction.

A mirror box integrating chamber is often used for this application. Four mirrors are mounted together at the edges to form a box or tube. The light is directed into this chamber, it reverberates about. In the process it arrives at the negative / slide totally diffused.

Such integrating chambers cannot eliminate dust spots, but they totally diffused light acts to suppress the visibility of dust on photo materials. Let me add that the end of the mirror tunnel, next to the negative / slide is covered with milk glass or milk plastic (white translucent diffuser).

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  • \$\begingroup\$ I was aware of the integrating chamber but I had totally forgot about it, thanks! indeed a good idea. I was not aware of the chamber made of mirrors, also interesting. I guess I can look up online about the optimal ratio width/length of the mirrors, but if you know already, please add it. Collimated light would be nice and I just learned that it works also with an integrating chamber! can you please add for clarification upload.wikimedia.org/wikipedia/commons/thumb/2/27/… \$\endgroup\$
    – FarO
    Mar 28, 2023 at 9:06

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