Full-spectrum lighting does not improve sales at restaurants

[Paul_in_Maryland]

Interesting article.

[That_Guy]

No shit. "Full spectrum" is nothing more than a BS marketing term invented to allow companies to charge 10x more for high color temperature, high CRI light sources for the purposes of ripping people off (mostly New Agers, and many "full spectrum" light sources aren't even high CRI).

Sorry, I'm in a ranting mood today. Add "full spectrum" to the list of things I hate next to "lux @ 1m".

[JohnB]

I ran a rest in my previous life and I am not surprised by this. Food and Beverage operations also tend to be tight with capitol expenditures so I would be surprised if this were widely adopted.

[TPA]

One restaurant alone isn't going to convince me either way, especially when their CONTROL changed. High CRI fluorescent lighting does make a difference, but I'm not sold on full spectrum lighting.

That said, I like the crispness of ~3100K lighting for retail & business, but prefer much warmer lighting for "intimate" settings such as restaurants and bars and sitting/relaxing areas in commercial spaces. I usually like to light these types of areas with theatrical lighting gels, with the 1/8 (tungsten) & 1/4 (fluorescent) minus green filters in place. At $6/sheet, it's far less expensive than the full spectrum bulbs and the effect is stunning. I only use enough so that skin takes on a warm, healthy appearance. I think this is the effect those pink colored lights in some restaurants were trying to achieve, but they usually took it waaay too far into the pink color.

[jtr1962]

Not surprising, especially if they were using the higher grade (CRI 86) of triphosphor tubes before the switch. The differences between the higher grade of triphosphor and more expensive full-spectrum tubes are subtle. Even I have a hard time telling the difference. Now the difference between cheap T12 cool white and anything T8 is dramatic. Even the lower grade T8s make a place look way better.

All that being said, you can get decent full-spectrum tubes in bulk for maybe $5 a tube. They're often constructed better than commodity T8s, and last about 50% longer (rated life 34,000-36,000 hours versus 20,000-24,000). That makes the effective price per tube more like $3.25 when compared on a weighted basis. The higher grades of triphosphor T8 run about $2 in bulk. The extra color rendering is worth the $1.25 more per tube. Over their lifetime, the biggest cost of fluorescent lighting by far is energy, not purchase price. On the other hand, those charging $20 and up for full-spectrum tubes are ripping you off. These tubes only cost marginally more to make than commodity tubes. So yes, I still think full-spectrum lighting is worth it, but only buying in bulk from reputable places, not from retail stores which overhype them, then charge four times as much.

[lyyyghtmaster]

Not to mention, (rant, rant!) that retail, brick-and-mortar stores often label things "full spectrum" when they're really standard 82~84 CRI triphosphor. The only difference I've found between CRI 90~92 tubes and standard is that they're dimmer because they emit more deep red and less (more visible) slightly reddish-orange (613nm) to come up with the same white balance. This takes care of some of the "orange popping" effect of normal triphosphor. The blue is also a bit more spread out, but that seems mostly unimportant.

This deep red is given a "special" rendering index (R9), which is near zero for standard triphosphors, but fairly high for CRI=92 and even higher for the premium full spectrums. Most objects have no or very little deep red pigment in them. Consequently, this lamp type can be satisfactorily neglected from consideration in most applications.

However, I have found one (very special! ) kind of red velvet that responds strongly in this range. Using it, I test ALL "full spectrum" light sources in use that I run across! (I keep a small swatch of it in my wallet. I would not DARE admit this fact most anyplace except CPF!!) A couple years back, The Home Depot carried a TCP 14W Springlamp that was 5500K. They were about $12.00/three pack. There's a picture of a little girl studying on the package. It was NOT labeled full-spectrum but, in fact, most certainly was!! Then they came out with a whole line of 5500K lamps, including a replacement to the 14W, and the deep red output is gone.

Incidentally, there exists at least one inexpensive, T12 old-style linear fluorescent tube with a high R9 value, and a fairly lavenderish appearance: the Sylvania Cool White Plus.

In the meat aisle at your favorite grocer, uncooked red meat is supposed to have a lot of R9 response due to the blood. Therefore, actual full spectrum lamps, often a 3- or 4000K high-CRI Metal Halide, are frequently used in this application. Note that "full spectrum" is not locked into 5000 or 5500K CCTs.

Incidentally, there exists at least one inexpensive, T12 old-style linear fluorescent tube with a high R9 value, and a fairly lavenderish appearance: the Sylvania Cool White Plus. It is not a triphosphor-based lamp. I don't know if it is R9-supplemented halophosphor, or something else.

A notable exception to the rule of unnecessity of full spectrum lamps would be print shops. They often use the higher CRI (like 96~98) tubes that have a much less "spikey" spectrum than 92s, and are not triphosphors. It's interesting to note that the "special" R9 (and others) rendering indices above 8 are NOT included in the standard CRI spec that everyone lists, although they usually have high R9 values anyway.!

Does anyone happen to know the exact peak or dominant wavelength center of R9?? 660nm seems to work well, but this might not be exactly on.

Why do I care so much about full spectrum and R9 rendering if these lamps are usually unnecessary? Because it's a cool effect, it's sometimes beneficial, and the theory also applies to white LEDs, which are poor in deep red.




WARNING: POSSIBLE CFL BELIEF-SHATTERING INFORMATION FOLLOWS.



Warm white (2650~3100K) CFLs are supposed to be a direct replacement for incandescent bulbs, and on a white surface, and many (most?) other surfaces they are. But have you ever tried comparing skin tones under both types? The CFL is not full spectrum; as far as I know they don't exist in warm white CFLs. (If you know of any, PLEASE, PLEASE post!!)

Under it, compared to an incan, light skin tones are made to look a funky pasty, tan-ish-makeup-like color! This might actually make people who use makeup very happy! Many people would say the difference is slight, but it's definitely there! I suspect it's because the blood beneath the skin is not being properly rendered, due to the lack of deep red. You're seeing more of the skin's native color, while excluding the blood. I have not attempted to do a similar comparison at 5500K, but I will!

I hope all this helps somebody. Please feel free to augment/correct it in additional posts!

[greenlight]

Maybe if they lowered their prices I would buy more..