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EddyCurr
11-10-2013, 12:26 PM
If you make the conscious decision to choose, what colour
temperature do you prefer for general shop lighting? For
task work?

Soft/Warm White at 2,700 K
Day Light at 6,500 K
Something in between.
The question comes up after shopping last night. The Philips
boxes indicate watts (actual and incandescent equiv), lumens
but no number for colour temp - only a description.

In discussion, a clerk tried to assert that a Day Light was brighter
than a Soft White for any given wattage. No so, said I - the lumens
designates effective output and as it happens, a Soft White 60W
had a nominally higher lumen rating than a Day Light 60W. Ah,
he replied, but the "perceived" brightness is greater for the Day Light.

I certainly perceive DL to be more harsh. Brighter? I'm not so sure.

.

oLo
11-10-2013, 12:41 PM
I agree with you; not brighter if the lumens are the same. The color temp really only has a bearing when needing accurate color comparison. Our brains compensate and normalize for whatever light we are viewing - sorta like a built-in white balance.

EddyCurr
11-10-2013, 01:08 PM
The color temp really only has a bearing when needing accurate color
comparison. Our brains compensate and normalize ...I wonder.

In this community, a pilot project to substitute LED for the existing high pressure sodium
lighting is under way. I haven't come across figures for the lumen rating of the two
systems, but if I make the presumption the lumen numbers are similar, I have to conclude
that the LED units are less effective at illuminating than the HPS units.

The warm orange light from the HPS lights tree trunks, branches, fences, sidewalks
and pedestrians along the boulevards, pushing back the darkness. In contrast, the
the blue/white light of LED units here projects down like a focused spot - lighting a
confined region and nothing more. Maybe it is the lense/diffuser instead of the colour.

.

SteveF
11-10-2013, 01:59 PM
I went through this a few years ago and settled on the 4100K bulbs. Tried the 6500K and the light has a bluish glare. Side by side with a 4100K they very much look bluish.

Steve

CarlByrns
11-10-2013, 02:16 PM
The warm orange light from the HPS lights tree trunks, branches, fences, sidewalks
and pedestrians along the boulevards, pushing back the darkness. In contrast, the
the blue/white light of LED units here projects down like a focused spot - lighting a
confined region and nothing more. Maybe it is the lense/diffuser instead of the colour.

.

Not a bad thing if you like to look at stars.

darryl
11-10-2013, 03:17 PM
Most of my fluorescents are still working, and at the time I installed them, I settled on a mix of one soft white and one day-glo tube for each fixture. Two warm whites didn't give enough sharpness to my perception of things, and two cool whites just didn't give a comfortable light. For me it was not a matter of 'getting used to' the color of the light- I had to arrange to provide a comfortable lighting to work under.

Bluish led lighting is not comfortable at all. I was happy to find the 3000k led lights that I'm using now on the mill. Seems pretty much optimum for that application.

I have some 50 watt halogens that I scooped for cheap a couple years ago. Just yesterday I found some compact fixtures that had the right sockets for these bulbs. These give a nice light, but you want to avoid looking at them. I like the fact that they give off heat, which is nice in the cooler weather. Even an extra 50 watts at the workbench helps keep me from wanting to turn the thermostat up. The fact that they are inefficient is then of no consequence.

If I look at this strictly from the standpoint of comfortable lighting, then it's the 3000k leds that 'shine'.

becksmachine
11-10-2013, 03:28 PM
The thing I have noticed is that if there is even a small amount of sunlight available, in addition to whatever artificial light is present, it seems to make a very noticeable difference which seems to become more and more noticeable the older my eyes get. :p

How well the "Daylight" designation replicates actual daylight, I am not sure. But all of the fluorescent fixtures in my shop have "Daylight" tubes in them to supplement the metal halide HID fixtures. Better color rendering has advantages as well. I find it nearly impossible to see the grey, etched text on end mills and taps under the HID fixtures but if I move under one of the fluorescent fixtures it becomes at least readable.

Dave

J Tiers
11-10-2013, 03:55 PM
What I have done is put one cool white and one warm white in each fixture. I do that in the seed starting area also, the plants seem to like it.

I find that mix is pretty good for visibility, as well as being easy on teh eyes. I've seen some places with that ugly blue fluorescent bulb type, (might be a species of cool white) and I'd hate it. It's not a bit like sunlight to me.

Mark Rand
11-10-2013, 04:44 PM
The workshop's got 5500K fluorescents at 20W/m^2 (2W/ft^2). that works very well. Higher colour temperatures look good but only if you have sufficient brightness. Kitchen's currently got 2700K LEDs to replace the previous incandescent bulbs and is looks distinctly yellow. Brigheter higher colour temperature bulbs may be substituted sometime in the next decade or so..

RussZHC
11-10-2013, 05:09 PM
Difficulty I have had is trying to get close colour matches across several types of bulb...we got new LED installed near the front reception area and the hassle trying to match those incandescent and CFL that were not replaced...close is about all you can hope for...I think there is also the matter of perception, bluish will often look bluer next to a yellowy-orange and less blue next to one that is "pure white"

EddyCurr
11-10-2013, 06:13 PM
The colour match issue is where bulbs with Kelvin numbers helps.
Although, if one goes by the word description, it is possible to get
what is sought as long as you head out shopping armed with an
understanding of where along the temperature range a given
description is located.

The 60W equivalent Cree LED bulbs just installed in some receptacles
are a match for the colour of an existing Warm White incandescent.

.

KJ1I
11-10-2013, 06:19 PM
I went through this a few years ago and settled on the 4100K bulbs. Tried the 6500K and the light has a bluish glare. Side by side with a 4100K they very much look bluish.

+1 This is exactly my experience. I, too, find "daylight - 6500K bulbs" way too blue and hard on my old eyes. So the shop is lit by 4100K's. I also find the "soft white" bulbs don't yield as much definition to objects.

Gravy
11-10-2013, 07:22 PM
I find "daylight" as applied to 6500K fluorescent tubes to be a misnomer. It should be called "skylight" because the light color & quality is actually closer to what comes through a skylight when the sun is not at the right angle to shine right in. It's the cold light from a blue northern sky or a gray overcast.

It's great for picking out surface details, but it makes me irritated and tired rather quickly. I mix in some warm white tubes in the ceiling fixtures, and have an assortment of task lights with fluorescent, incandescent/halogen, and LED light sources. If those don't work, I can usually drag whatever I'm looking at out into the actual daylight.

BambooGuy
11-10-2013, 08:03 PM
Lighting of my mini-mill has generally been relegated to cheap gooseneck lamps. Lousy at best.
A recent treasure hunt to one of the bigbox stores, found two items on the bargain/broken/returned bakers rack that helped formulate a solution. An open box 11 LED under-counter light bar, and a partially destroyed remote shower head kit. Both found for under $10.00.

The shower head hose looked vaguely similiar to the armored plastic that contains wiring to the
power switch and motor on the mill. Back in the lair, "Dremeled" the led light down to the basic elements of circuit board and A.C.power leads. A quick test wiring revealed a blinding array when out of the cracked (hense, bargain price) diffuser cover/mount.

Silicon RTV held the board to the 12 inch aluminum "C" channel, along with a milled slot vertical tab for mounting and adjustment. Cutting the shower head hose, and feeding the wiring thru the inner plastic lining provided current to the emerging lamp. Using the discarded "chip launching" shield mount and bolt, I found a "sweet" spot that washed the entire table and surrounding area in bright, white, wonderful light.

http://i1312.photobucket.com/albums/t535/BambooGuy/ledone_zpse608de30.jpg (http://s1312.photobucket.com/user/BambooGuy/media/ledone_zpse608de30.jpg.html)
http://i1312.photobucket.com/albums/t535/BambooGuy/ledthree_zps4a3d2d2e.jpg (http://s1312.photobucket.com/user/BambooGuy/media/ledthree_zps4a3d2d2e.jpg.html)
http://i1312.photobucket.com/albums/t535/BambooGuy/ledtwo_zps5d1046d8.jpg (http://s1312.photobucket.com/user/BambooGuy/media/ledtwo_zps5d1046d8.jpg.html)

Forrest Addy
11-10-2013, 09:09 PM
I used to do photography so I'm sensitive to color temperature. Back in my salad days I had an arty girlfriend who was a part time docent at SAM. I heard any amount of blather as to the best light for viewing fine art - enough to where I could draw my own conclusions with some justification.

Open noon sun at 5500K is too danm glaring. Warm colors tend to bleach out and look muddy. Further too much high spectrum leads to vision fatigue and eye strain. I HATE Walmart for the glaring light but not just for that reason.

Wamer colos 3200 - 2500K are more relaxing and suited for people to people but higher end color rendition sucks. You can hardly sort black socks from Navy blue for example.

I like overcast or later in the day 4000K light better for all practical purposes like study, cooking, work, including in the shop. Accordingly I pay about double for the 4200K Phillips flourescent tubes I use.

Note to self: a few of the big shop lights are flickering. Buy tubes at (Gasp!!) $75 a box

J Tiers
11-10-2013, 09:41 PM
One problem with the LED bulbs is that they often, or even usually, don't have a "spectrum", in the sense of having a continuous range. They have a small set of fairly narrow peaks spread across the visual range, sufficient to "fool most people's eyes".... but if you are like me, you rarely fall into the "most people" category.

I have never tried them for a color matching lamp, but I would not be encouraged by the idea that they totally lack output in substantial areas of the visual range.

ed_h
11-11-2013, 02:45 AM
One problem with the LED bulbs is that they often, or even usually, don't have a "spectrum", in the sense of having a continuous range. They have a small set of fairly narrow peaks spread across the visual range, sufficient to "fool most people's eyes".... but if you are like me, you rarely fall into the "most people" category.


This is an issue with most non-incandescent lamps. Though their peaked spectrum can be crafted to look the same as an incandescent of a certain color temperature, the way it makes the color of objects look can be much different than broad true incandescent light. How well a lamp renders colors of objects, compared to incandescents or sunlight is yet another measurement for comparison. Sometimes it's provided with the lamp, sometimes not.

J Tiers
11-11-2013, 08:48 AM
It's worth noting that the sun is in fact , an "incandescent" source.......! :)

The mix of phosphors can be made to do a pretty good job, and using different lamp types mixed can do even better.

Forrest Addy
11-11-2013, 10:54 AM
An LED is in effect a flourescent source. The LED part is an ultraviolet emitter that stimulates a phospher layer whose mix more or less emulates black body radiation.

Light quality has a marked effect on how long and how well I work on visually demanding tasks so it's something I pay attention to. I've worked under many lighting schemes and prefer the mostly daylight of the many windowed 30's era machine shop where I served the bulk of my career. So I determined natural light is best as in morning or afternoon through indifferenty cleaned industrial windows (the windows ran north and south). Thus my preference for shop light color temp is 4000 degrees K.

The buck seventy-five Costco daylight flourescent tubes my friend Mark has in his shop lights may be cheap but in an hour or two my eyes are looking for relief almost like the beginnings of a welding flash. Warm flourescents are far more endurable but unsatisfactory if color matching paints or stains are the job du jour. In the end I prefer incandescent light or as close as I can get to it. Sodium vapor light frankly sucks. So do yard light type mercury vapor - heap big glare; little illumination. Heavy service bulbs are designed to run cooler so their filaments are stronger when hot but their light is a little pink and you need a 100 Watt bulb to provide 40 Watts equivalent illumination.

Quartz halogen light to me has by far the best illuminating quality. It is, after all, true black body light emitted by a hot tungsten filament. In the past I used the lamp from my color enlarger when I needed really good light. Its quartz halogen bulb ran at 3800 degrees K and a special power supply protected it from brown outs and surges. Colors just pop under its beautiful white light. Problem is, the bulb is driven to its thermal limits and fails in 5 hours or so. The special bulbs aint cheap and they're getting scarcer so I looked for an alternative, more portable source than my humongous, costly to run enlarger.

I now have a $40 battery hot shoe style video light whose 8 x 8 LED array is so near the quartz light of my dichroic enlarger lamp I can't see the difference. I've looked at color samples under each light (separated by a dark opaque screen). If my observations mean anything the LED video light renders colors faithfully to hazy afternoon sunlight. This LED video light is my de-facto reference source for flourescent tube evaluation. So long as Phillips doesn't screw up the phosphor coating of their CR 4100K tubes, theirs will be the ones I buy - and my little LED video light gives me the means to evaluate them with some reliability in the box-store's comparison display.

So far I haven't found an affordable LED replacement for my shop lights. But time is marching and innovators are hard at work.

I'm looking forward to the day when 100,000 hour light sources are on the market which not only dim but whose black body color temp can be dialed up or down. 10% of our energy output is used for lighting in one form or another. LED's last 30 times longer than incandescents and use 1/10 the energy. The imperative is there, smart people, so get cracking.

EddyCurr
11-11-2013, 11:47 AM
One problem with the LED bulbs is that they often, or even usually,
don't have a "spectrum", in the sense of having a continuous range. The Cree bulbs come in both a regular and a TW series.

The TW series is said to have a Colour Rendition Index of 93 (out of a CRI scale of 100).
Apparently, this is achieved through the application of the element neodymium to the bulb's
glass. The coating gives the glass a blue hue when the bulb is not lit, but the colour of the
light when lit is equivalent to the expected light for a bulb of similar colour temperature.

I notice that the wattage for the Cree TW series LED bulbs is nominally higher than for the
regular uncoated Cree LED bulbs.

The TW bulb product page (http://www.cree.com/Lighting/Products/Indoor/Consumer/40W-Replacement-TW-Series-Soft-White-LED-Bulb) has some links to pdfs with remarks and spectrum graphs. (http://www.cree.com/~/media/Files/Cree/Lighting/Lamps/Bulb/TWseriesFAQ.pdf)

Navigate out a level or two for information about the other variations.

.

EddyCurr
11-11-2013, 11:55 AM
A recent treasure hunt to one of the bigbox stores ... helped formulate a solution.Nice work on the lamp, thanks for sharing.

Is a splatter shield a future addtion?

.

EddyCurr
11-11-2013, 11:59 AM
I find "daylight" as applied to 6500K fluorescent tubes to be a misnomer. ...
It's the cold light from a blue northern sky or a gray overcast.This articulates the issue VERY well.

.

J Tiers
11-11-2013, 09:29 PM
An LED is in effect a flourescent source. The LED part is an ultraviolet emitter that stimulates a phospher layer whose mix more or less emulates black body radiation.


Not so fast..... the mix of phosphors is what determines the spectrum. Black body it is not.

Interestingly, the CREE folks claim CFLs have the very problem that manufacturer graphs often show for existing LED bulbs.... narrow spikes of emission.

of course, that would then be equally true of ALL fluorescent bulbs, but in fact, many have a good CRI, and a wider spectrum.

The truth is that ANY source can be used to stimulate the generally same sort of phosphor set.... A fluorescent uses the mercury arc spectrum, with a fair amount of UV, as the energy source. An LED source can be much the same , or different.

While the choice of a source can affect the possible list of phosphors that are usable, there are a large number around, and it's possible to choose them to get good results. A bad light probably reflects a bad choice of phosphors, more than some inherent deficiency in the system of energy input, be that mercury arc or LED.

Forrest Addy
11-12-2013, 01:19 AM
[QUOTE=J Tiers;885366]Not so fast..... the mix of phosphors is what determines the spectrum. Black body it is not.

JR, not so fast... note the qulaifiers I iwrote but you omitted: "more less emulates" meaning "approximates." I never said or meant to say "is" or equates" or identical to" I'd call my statement well quarded by qualifiers. Look before you leap.

Otherswise you are entirely correct about the mix of phosphors determining the emmision spectrum. Mix them just so and you get close to the ideal.

ed_h
11-12-2013, 01:27 AM
An interesting article on fluorescent phosphors:

http://www.electrochem.org/dl/interface/sum/sum98/IF6-98-Page28-31.pdf

It is pretty technical, but it talks about the original "cool white" lamps using a simple phosphor and more modern, high-CRI lamps using a blend of three or even five different rare-earth phosphors to more closely emulate black body radiation.

mattthemuppet
11-12-2013, 04:47 PM
I like around 4500K, which corresponds to around the 4 tint bin for Cree LEDs (3 is ~5000K and 5 is ~4000K I think), and aim for a minimum 80CRI. Some shop lights I built recently use Nichia 119 LEDs (can't remember the part code) which are ~4400K and 90CRI and give off a lovely light. They're also awesome now it's getting cold as they're not effected by the temperature, if anything they should be marginally brighter the colder it gets. Here you can see them compared to a standard 2700K CFL (please excuse the mess):

http://i1349.photobucket.com/albums/p752/mattthemuppet/light%20bar%20build/IMG_3059_zpsc13156e1.jpg

As for LEDs approximating the wavelength distribution of incandescent light, that's 100% correct. LEDs are all blue with varying thicknesses of phosphor slapped on top (hence the sharp peak in the blue part of the spectrum). Thin phosphor lets more blue through and converts less to red, which makes the LED more efficient (lumens per watt) but a cooler white with poorer CRI. Thick phosphor blocks more of the blue and converts more to red, which improves CRI markedly and warms the tint, but at the cost of lower efficiency. The highest Cree bins (lumens/watt) are always cool white (>6000K) and have min. 65CRI. To get 5000K and 75CRI you have to step down a bin and to get 80+CRI you go down another bin (or two). That's simplifying it a bit, but it's enough to understand what's going on :)

LED lights are seriously easy to make and LEDs aren't that expensive - the light bar I made was about $10 and the desk lamp retrofit was perhaps $13, $10 of which was for the lamp. You could scale it up with some long C/U channel to make a fluorescent tube replacement for around $30 (plus metal cost) and ~1000 or so focused lumens. Or you could buy some Nichia Elara strips which would be considerably easier.

KJ1I
11-12-2013, 05:55 PM
http://i1349.photobucket.com/albums/p752/mattthemuppet/light%20bar%20build/IMG_3059_zpsc13156e1.jpg



Finally. Someone with a shop that looks like mine!

mattthemuppet
11-12-2013, 06:57 PM
there's always something more interesting to do than tidy it up :)

mike4
11-12-2013, 07:25 PM
I recently bought six LED replacements for the worklights above one of my benches , the difference is chalk and cheese .
Leds are brighter and clearer.
Michael

Shuswap Pat
11-13-2013, 12:16 AM
I just finished building a shop - 1000 sq ft, 12' cieling and installed 6 x4tube T5 high outputs - polished reflectors- 35watts - 5000K colour temerature.

I am very pleased with the result.

Patrick