On Sunday, January 4, 2015 7:02:37 PM UTC-7, Arfa Daily wrote:

I don't like CFL lighting - that's well known. I am still reserving judgment
on LED lighting. My local supermarket recently had a major refit, and all of
their ceiling fluorescent fittings were replaced with linear LED arrays, so
at first, you don't notice that anything has changed. When I did realise, I
was surprised that the quality and intensity of the light in terms of how
well it illuminated the sales floor, was every bit as good as the original
fluorescents. They also have replaced the car park floodlights with LED
arrays, and these are crap compared to the metal halide fixtures that they
replaced. My hairdresser has replaced all of the mini spots in his ceiling
fixtures with equivalent LED bulbs. They produce a good amount of light, and
the colour is not bad, but they are unpleasantly bright to look at. They are
also not a very good shape and don't fit the fixtures terribly well. I'm not
a great fan of LED street lighting either, as I think it is harsh in
comparison to say LPS, and nothing like as effective at penetrating fog, as
it is polychromatic light. It also doesn't seem as good at producing 'even'
street lighting as LPS or even HPS is, if you can get past the yellow colour
of those types.

I've been a regular visitor to Hong Kong since 2010 and just returned from the worlds largest LED lighting show again in October. I import commercial retrofits that are years ahead of what is available (or "hawked") here in the US. As such, I have quality products and I'm aware of the crap that is out there. My background is in lighting, electronics, television and cinema and I'm well aware of color temperature and lumens. Unfortunately, the customer whose heart is in the right place is usually a victim in cases like you describe. The hacks that sell LED retrofit by-and-large have no clue as to what options are available as they only re-sell what some distributor (or DIY store) has in stock. There are success stories but most likely they are due to dumb luck and not any engineering. Don't get me started on their lack of optical knowledge, lumens, color temperature or the relationship of rods and cones to pupil lumens, CRI, and the horrible spectral response of HPS lamps. I have relations with over 30 vendors in China and I can't tell you how cool and well-made the lamps are becoming.

Here is a brief overview of light and the eye:

Cones and Photopic vision- The central part of the eye is the fovea that is rich in a type of cells called 'cones'. Cones are responsible for color vision and are involved in vision during bright light. This is called Photopic vision.

Rods and Scotopic vision-Rods are sensitive to dim light and are active during low light intensity conditions. Rods cannot perceive color. Vision due to rods is 'black and white.'

Light measuring instruments measure Light intensity in Lumens - considering only the response of the cones. Thus, the Lumens measured by a light meter are also called Photopic Lumens.

In conditions of low light intensity entire vision is due to rod cells (scotopic vision). In medium light intensity (conditions as are often found under street lights and in homes) vision is called Mesopic vision and is due to both rods and cones. Using 'Photopic Lumens' to describe light intensity in such an area grossly underestimates the light intensity as it totally ignores the contribution of rod cells to vision.

And I hate CFLs, too.

Yours truly,

Mr. Klay Anderson, D.A.,Q.B.E.