The overhead domelight/reading light in our LS400 was an improvement over competition for its time,

Toyota did exploit parabolic reflectivity in its design of the reading light portion of the combination lamp assembly, but did far less in the dome lamp portion of the assembly.

This post focuses on improving the dome lamp portion to increase reflected luminosity and uniformity through use of high temperature outdoor grade reflective aluminum foil with pressure sensitive adhesive applied to reflecting surfaces ..
I extracted the lens/housing assembly, carefully separated the lense and observed the housing/internal reflecting surface is off-white.. with a non-polished metal channel serving as a heatshield/relector for the festoon bulb.....leaving room for improvement.

An online resource provides reflectivity data on various colors and surface materials...aluminum foil offers at least a 20% improvement over the OEM's off white matt plastic housing.

see:

http://www.engineeringtoolbox.com/li...or-d_1842.html

Material Reflection Factor
(%)
Aluminum, pure, highly polished 80 - 87
Aluminum, anodised, matt 80 - 85
Aluminum, polished 65 - 75
Aluminum, matt 55 - 75
Aluminum coatings, matt 55 - 56
Chrome, polished 60 - 70
Vitreous Enamel, white 65 - 75
Lacquer, pure white 80 - 85
Copper, highly polished 70 - 75
Nickel, highly polished 50 - 60
Paper, white 70 - 80
Silvered mirror, behind glass 80 - 88
Silver, highly polished 90 - 92
Oak, light polished 25 - 35
Granite 20 - 25
Limestone 35 - 55
Marble, polished 30 - 70
Plaster, light 40 - 45
Plaster, dark 15 - 25
Sandstone 20 - 40
Plywood, rough 25 - 40
Concrete, rough 20 - 30
Brick, red 10 - 15
Paint, white 75 - 85
Paint, medium - 35
Paint, dark blue 15 - 20
Paint, light green 45 - 55
Paint, dark green 15 - 20
Paint, light yellow 60 - 70
Paint, brown 20 - 30
Paint, dark red 15 - 20

Dome/reading light assembly showing highly polished relectors for reading lamp bulbs but not the main domelight festoon bulb.....more of a heat shield and the matte off white surface does not offer optimum reflectivity....although the plastic lense does a lot to improve diffusion...

Aluminum foil added using cash register paper as a template. I elected to remain clear of the festoon bulb but improve the adjoining surface reflectivity. Visibly improved reflectivity with foil over stock plastic surface
Nashua brand high temperature outdoor rated aluminum foil tape with high surface energy adhesive.
Paper cash register tape used for templating aluminum foil.

 

I wonder what would happen with a set of LED bulbs and this added reflectivity? Nice bright car, I should imagine!

 

the better LED Bulbs of this type are usually directional, so the surrounding is less of a concern.

 

LED' light output is directional (vs incandescent bulb envelope of 360 degrees) thus notorious for "hot spots"...the closer the LED to the lense, the less diffusion occurs and more prominent hot spots .think LED tail lamps in most contemporary automobiles...they look like cheap rope LED lights have been inserted as a last resort.

This domelight is not bad but to my eye the reflector was not optimized. ..one side is brighter than the other because the festoon bulb is not centered and the reflector is right angle and inclined vs parabolic..

An improved reflective surface will significantly aid incandescent or LED (an LED with proper diffusion) illumination.

Significant improvement with uniformity using foil with OEM incandescents....almost too easy

 

Yodaone, I am working on a conversion to LED project in a museum setting at the moment and have been so sold on our quality of light, cost savings and the longevity of the units we are using I totally forgot about the directional properties of the units. Thanks for reminding me. In a small, car-based application, you are very right. The directional disability of the average auto version of interior LED lighting would be problematic at best.

 

CREE LED produces quality light engines for OEM, and commercial/residential LED bulbs. Attached is CREE LED data sheet depicting component sized light engines that would work with 12VDC. Many items should be available from Digi-Key or Newark Element 14.

 

getting most use out of that roll of foil are we? haha just teasing and I do enjoy these threads. I too am a lighting enthusiast (the ricer in me), and can appreciate a good lighting setup when done purposefully and tastefully (the anti-rice in me).

LED technology is soaring. I read awhile back on remote phosphor LEDs!
http://www.ledinside.com/press/2015/...r_led_lighting

 

Thanks for keeping my interest with these quirky lighting threads, I would've never thought to upgrade the reflective surfaces behind the lights One small piece of advice, so I can visually see the difference, could you post before and after pics of the light output to see what effect this foil tape has on lighting? I think it would reinforce your points that much more.