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Ovoid, Graduated, ND filter design help request.

Ovoid, Graduated, ND filter design help request.

Ovoid, Graduated, ND filter design help request.

Challenge:  working on a fine-art lighting application, per guidelines in ISO 3664-2009, but using near-subject illumination source (MR16, LED flood bulbs), with either common track light or frame-mounted lighting fixtures.

Problem: Non-uniform, luminance distribution across artwork. Attempting to disign a special ND filter (2" dia.), to mount in front of light source to balance illumination lever across surface of artwork, and minimize surrounding "halo" of light. Conventional photographic ND filters are graduated only in one axis and most are dye-based, subject to rapid fading under intense luminous flux.

Concept: Thinking of using a glass disk with an opaque CVD coating (perhaps aluminum?), then dry-laser etching a pattern of slits in an ovoid pattern, inversely related to the measured lumination distribution, to attenuate the "hot-spot" and equalize the light distribution. May need to have a diffusive front surface (i.e. "frosted" to avoid any projected patterning of the slits.

Goal: Must be producable at low cost and scalable for other common light sources. I have access to local CVD and laser etching sources, for prototyping and limited production.

Questions: Is this concept logical or even optimal? Any suggestions on pattern geometry? I am looking for some suggestions or other input that might help me solve this problem.

RE: Ovoid, Graduated, ND filter design help request.

A holographic filter would work well for all required specs... except maybe the low cost part.

Dan - Owner

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