Bill Tindall, E.Tn.
Actually, at this point conclusions will be provided. When I figure out how to present all the data I will do it at a later date, if there is interest.
1. 4 lamp T5HO fixture with 2 lamps removed, 3 year old lamps, 5000 lumen per lamp specification, 4500K, 85 CRI. Cost at the time I bought $80
2. Lowes LED 3800K, 80 CRI, 4000 lumen, $50. (new)
3. Max Light LED 5000K, 4100 lumens, no CRI provided, unknown cost (new)
The LED fixtures were provided on loan by our club president.
Measurements were made for each fixture at identical working distance from light source to same place on my bench. Measurements were made directly under the center of the fixture to determine comparative direct foot candle illumination of the bench surface by each source. Measurements were made at bench height at 1, 2 and 3 feet from center to determine focus of the light. Measurements were made 18" from center at various distances below lamp to measure side spread of light.
Data: Illumination directly below center of fixture was 140, 50 and 45 foot candles for these three fixtures respectively, 1,2,3.
1. The illumination measured directly below each fixture was approximately proportional to the stated lumen output of the fixture.
2. Furthermore, the illumination measure at 1, 2 and 3' across the bench was proportional to stated lumen output of each device.
3. Measurements made at different vertical distances from the lamp, 18" off center showed the T5HO light was more focused downward than either LED.
4. Light measurements for each LED were nearly identical.
Overall conclusion: The data on the boxes for these fixtures provides an accurate guide for the illumination to be expected upon installation. Lumens per dollar less for T5HO.
When the Max Light was turned on there was an instantaneous adverse response from a bystander. "That light is harsh. It leaves me agitated. Turn it off." The CRI of this lamp was not provided on the box. I believe it is likely poor and the adverse response was to the quality of the light and not the temperature. I get the same response from poor CRI fluorescent lamps.
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- Fluorescent vs LED- data from experiments