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Fluorescent vs LED- data from experiments

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Fluorescent vs LED- data from experiments

#1

Fluorescent vs LED- data from experiments

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.

Fixtures compared:

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.

Conclusions:

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.

Re: Fluorescent vs LED- data from experiments

#2

What is "CRI" Please


Re: Fluorescent vs LED- data from experiments

#3

Explanation of CRI

Bill Tindall, E.Tn.

Color Rendition Index

I don't know the details of how it is measured but the result is easy to explain. We have sun light and we have man made light from some lamp or another. If an object looks the same in this artificial light as in sun light the CRI is 100.

If the CRI of some artificial light is 93 likely only an expert in color matching could tell a difference from looking at it in the sun.

An artificial light has a CRI less than 100 because there is some color component of the artificial light that is missing or out of balance. In the case of the experiment I reported on the Max Light LED, this lamp was likely deficient in red and green which made the light harsh. (LED lights are inherently blue and need to be made redder and greener by some means. A cheaply made LED might skimp on adding these colors. )

You have probably seen the yellow "sodium" lamps used for street lighting. Stuff looks strange under their illumination. I don't know their CRI but it might be 20, or some other small number.

CRI is critical to color matching. You can be sure that the lamps lighting the paint strips in Lowes are very high CRI and the same for a designer clothing store. But crappy CRI can also have a psychological component, as demonstrated by the adverse reaction the bystander had to the Max Light or I have to crappy fluorescent lamps with a CRI of 60 or 70.

Re: Fluorescent vs LED- data from experiments

#4

T5HO vs LED

John K Jordan

I've made similar but very casual measurements to compare my T5HO fixtures with some of my LED fixtures. I'm glad I installed the T5s. The light is incredible.

A longer-term and harder evaluation is the light reduction over time. I read where tests showed some LED elements lost a considerable amount of light output over a few years. This would never be noticed with the eye since it is so gradual.

JKJ

Re: Fluorescent vs LED- data from experiments

#5

Re: Fluorescent vs LED- data from experiments

Barry Irby

I went to

https://www.fullspectrumsolutions.com/pages/cri-explained

And read about CRI. Very interesting and somewhat confusing. Bill is right about low pressure sodium vapor lights, CRI is 0, High pressure ones are 25.

Incandescent bulbs are considered 100. But there are caveats.

Cool white fluorescents are 62, interesting.

They have a long and interesting list. It's on the Internet, so it must be accurate.

As an aside, I got two 2' x 2' troffer lights with LEDs for free. Stuck them up in relatively dark corners of my shop. (There, I fixed it) Lets just say the results were underwhelming. They are not noticeable. I walk in and turn the lights on and am completely unaware of the new lights.

Re: Fluorescent vs LED- data from experiments

#6

Re: Fluorescent vs LED- data from experiments

Tony - Memphis

My wife is an artist. We've purchased lots of bulbs from them. Recently, I replaced the tubes with LED tubes that have high CRI. She really likes them. She has two 4' double bulb fixtures and a ceiling fan 4 A bulbs that we got from them - Blue Max I think? She is pleased with the setup. I have gotten in the habit of bringing my color samples into the house to look at them in place. We have such a wide range of light color nowadays.

I remember reading a passage in Mr. Dresdner's book about a customer approving a finish, then being very upset upon delivery. The lighting in the shop was different than the customer's sight and....

I've really learned to appreciate the value of more light! (53 this year).

Re: Fluorescent vs LED- data from experiments

#7

color of fluorescent light

John K Jordan

>>>Cool white fluorescents are 62, interesting.

I think the problem with fluorescents, at least the older bulbs, is the spectrum is not continuous as with black-body radiation (e.g. incandescents) but emitted in strong narrow bands due to the nature of mercury vapor and the phosphors used. Decades ago the common T12 (12/8" dia) bulbs used phosphors that put out horrible color, both for the eye but especially for film photography - even the special filters we bought to correct were not effective. Now fluorescent bulbs are made with very different phosphors for much better light.

A quick search brought up this article: https://en.wikipedia.org/wiki/Fluorescent_lamp

Search for "color" to get to the interesting parts about the light. There are photos and fascinating spectral charts.

JKJ

Re: Fluorescent vs LED- data from experiments

#8

What is considered "good" or "acceptable" CRI?

Tim Greif - West of Chicago

I've enjoyed the discussion, but am a little puzzled by the CRI concept. LOML asked me to install some 5000K, 100watt equivalent FEIT LED bulbs in an old down light chandelier in her work area. They show 90 CRI on the box and I find them pretty impressive for her craft and painting work. But that got me thinking - what's the lowest you'd consider as an acceptable CRI? All this discussion has talked about CRI but I've not seen anyone mention what constitutes a floor or bottom value for this index. Or is this purely subjective?

I have twin tube 30 year old T12 fluorescent fixtures in my 3-car garage shop (total of 13 fixtures). Most have cool white, twin 3000 lumen tubes, 4100K. Barry's post hints that they have a CRI of 62. I find them quite acceptable for my work, which runs everywhere from woodwork to car and motorcycle work. For me, replacing these with LED tubes makes absolutely no sense. At my age, I'll never see the payback from energy savings. And the light output is already acceptable for me.

So what's your take on minimum CRI that you'd settle for in any light source? Just curious.

Re: Fluorescent vs LED- data from experiments

#9

depends

John K Jordan

I think it depends on who you are and what you are doing. An artist matching colors or creating his vision has different needs than a woodworker or welder. For most people and most tasks bright enough is the important thing. The eye adapts well to color bias.

I found out a mix of lights of slightly different color coming from different directions actually improves my ability to judge compound curves at the lathe.

Color is real important to photographers since light of different colors coming from different directions play havoc with shadows. I want shadows that look grey, not green like in this horrible picture of a Beads of Courage box where I had two unmatched lights. This drives auto white balance in cameras crazy and fixing it in Photoshop is such a pain it's usually not worth the effort.


JKJ

Re: Fluorescent vs LED- data from experiments

#10

CRI 90 is very good

Bill Tindall, E.Tn.

90 CRI is a very good lamp for most anything. There will not be any colors missing at 90. I think it would take a sensitive person to detect any improvement above 90. I find CRI 70 annoying to work under. Colors are missing from the spectrum. My current shop lights are CRI 85 and I find them acceptable.

Re: Fluorescent vs LED- data from experiments

#11

Re: CRI 90 is very good

Barry Irby

How would anyone know what the CRI is? I have a mix of fixtures and bulbs. Is there a way to measure the CRI or Do you have to read it off the packaging, in my case, the long gone packaging.