Sunday, March 12, 2006

Diffuse lighting conversion kit

The default lighting arrangement in my room is of the sucky one-bulb-in-the-middle-of the-ceiling kind. Since I like to push the desks right to the walls, and since light travels in straight lines (if you adhere by classical optics), my head would create a shadow exactly where my reading material/work papers would be.

I have a bright desk lamp, but as previously mentioned, bright. Directing that halogen bulb on the desk gives too great a contrast between the illuminated patch and everywhere else.

In the past, I have tried shining that lamp onto a nearby wall for diffuse lighting, but that strategy results in too much wastage (I want the light diffused back downwards to the desk, not horizontally across the room).

Yesterday, I thought it would be nice to have a sheet of dull reflective material above the light to act as a diffuser.

Paper would do nicely.

But paper does not reflect all the light that fall on it; some of it is transmitted and diffused behind it, which is a waste of perfectly working photons.

Aluminium foil backing! Foil is very light weight and highly reflective, making it a suitable candidate. A small bonus of the foil is that it acts as a heat shield, protecting the extensive cellophane tape fasteners from possible degradation by heat.

A sheet of foil was folded to slightly smaller than the A4 sheet and its corners taped down. Since the foil is very fragile, another sheet of paper was layered above the foil to protect it in a sandwich of plant fibre sheets.

A system of supports was made for the diffuser sheet. Since the loads would mostly be bending loads, the supports were made with reasonably large cross-sections. As anyone will probably conclude, the truss system appears over-engineered…

[Intermediate steps skipped to preserve the continuity of this article. Also, I stopped taking photos while working.]

Finally, the entire assembly is installed onto the wall directly above the light. Illumination at the table improved, but whether this improvement is justified for the effort required and the diffuser's intense ugliness is subject to personal opinion.


What a joke. The whole contraption flopped over and died less than 24 hours since the diffuser was erected. The adhesion between the cellophane tape and the slightly coarse wall was less than ideal. In the intervening time, I thought of a concise solution to all those ugly truss work.

This time, the supporting structure was simply two sheets of cardboard cannibalised from a cereal box. Fortunately, they were about the size of an A4 sheet and no modifications were necessary.

The sheets were carefully layered: paper, foil, 2 cardboard sheets, and then brutally stapled together. No more messy cellophane tape. Yay!

A paper puncher was recruited to puncture exactly three (3) holes in the structure, and thread was used to attach the diffuser to an adhesive hook.

The end result is much more elegant than the initial design.

I’m quite sure if I had sufficient strips of expensive balsa wood, the end result would be excessively complicated.

Like this.

Clicketty click! (59 kB)


Blogger 小李飞刀 said...

Hmm.. I think I would have wrap 2 piece of A4 paper around the lamp to taper the EM field.

5:13 am, March 13, 2006  
Blogger Lao Chen said...

Yeah, that or lowering the diffuser.

7:14 pm, March 13, 2006  

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