Different color light from different manufacturers?

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DrSnowman

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Has anyone here noticed that the same K bulbs from different manufactures look a little different in color? I installed new 2' and 4' GE fluorescent T8 bulbs in place of Sylvania's with the same K rating that are cross referenced as equivalents by our suppliers but the colors look a little different.
 
There is no standard for how the led's will look at a certain temp. Some mfgrs. use cool white & warm white instead of using the kelvin scale.
 
180224-0757 EST

DrShowman:

To be expected.

See https://www.amazon.com/EISCO-Resolu...8-1&keywords=spectrograph#feature-bullets-btf

See additional information and comments. I did not realize that moderately useful low cost units existed. I had been aware of low cost gratings.

To looks at visible light color components you can use a prism or diffraction grating.

At Amazon I believe this one has an internal scale
https://www.amazon.com/EISCO-Premiu...fRID=9G1ATTE026C48F42G8SY#feature-bullets-btf

If you heat a material (blackbody), tungsten for example, then there is a continuous frequency spectrum of radiation starting a zero, increasing to a peak, and then decreasing. The hotter the material the higher is the frequency of the peak point. The temperature in Kelvin (relative to absolute zero) can be used to describe the color characteristics of the light source. This works well with incandescent objects.

The color sensors in the eye are tuned to approximately red, green, and blue. The sensors in two different people may not and probably are not (I have never studied this) tuned to exactly the same frequencies. Further they are not a very narrow band filters.

Fluorescent and LED light sources use chemical compounds called phosphors excited by ultraviolet light to produce light in the visible spectrum. These phosphors do not generate a continuous spread spectrum like an incandescent body.

To generate something that the eye sees as white is done by using various combinations of appropriate phosphors. The color output is given some K rating based upon its approximation to an incandescent source. Two different people may not see a particular phosphor source the same because of differences in their eyes.

Two different manufacturers of lights may not use the same mix of phosphors, and/or from batch to batch there may be differences.

See
https://en.wikipedia.org/wiki/Optical_spectrometer
https://en.wikipedia.org/wiki/Fluorescent_lamp

.
 
Like anything lowest bidder for the oem, thickness of phosphor, amount of mercury, voltage, the +/- of each part; it all falls within tolerance. Just look at a torque wrench +/-.
 
DrSnowman said:
I asked about 2' and 4' T* fluorescent bulbs not LED's. Thanks anyway.
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I think gar's answer is just as applicable to LED's that are intended to produce a "white light" as they also use phosphors to try to do about the same thing as fluorescent tubes are doing.
 
:thumbsup:

Basically, whenever the spectrum of a light source does not match a perfect black body radiation profile of amplitude versus frequency assigning a single Kelvin Coordinated Color Temperature (CCT) number must be done using a specific definition (formula) that integrates the full amplitude spectrum to get a number.
As a result, there are an infinite number of different spectra that produce the same number, but the impression of color to a viewer can differ greatly between any two.

With incandescent lights the same question did not come up to nearly the same degree [sic] because except as modified by various types of filter glass and coatings, the spectrum of a hot filament follows a black body curve and so two lamps of the same CCT should give an identical color impression.
 
Appreciate all the input but I asked a very simple question...Do the colors of different brands of the same K rating fluorescent lamps match perfectly or are they slightly different? Almost all of the light fixtures in our buildings are Sylvania. The boss has been ordering GE equivalents because he can get them cheaper. But the colors don't appear to match all the time. I was hoping to get some of you to say yes or no so I could show him this thread and prove that there is a difference. I want him to order Sylvania.
 
180224-1712 EST

DrSnowman:

The answer is the colors are unlikely to be exactly the same. So a reasonable answer is no. But you should have understood that from what I and others told you. Further you need to do some study and experiments to understand the problem. I gave you various links to look at.

I really suggest that you buy one of the inexpensive spectrometers and experiment. I think I would try the
https://www.amazon.com/EISCO-Resolu...fRID=DE2MV2DVTFYPG462WPC3#feature-bullets-btf

.
 
DrSnowman said:
Appreciate all the input but I asked a very simple question...Do the colors of different brands of the same K rating fluorescent lamps match perfectly or are they slightly different? Almost all of the light fixtures in our buildings are Sylvania. The boss has been ordering GE equivalents because he can get them cheaper. But the colors don't appear to match all the time. I was hoping to get some of you to say yes or no so I could show him this thread and prove that there is a difference. I want him to order Sylvania.
Click to expand...
It was mentioned you can even have some difference from batch to batch on the same line.
 
180224-2115 EST

DrSnowman:

Are you saying that you see a color difference, but your boss can not? If bulbs from two different manufactures are in the same fixture, then it should be easy to do a color and intensity comparison.

Your boss might have a color blindness that prevents him from seeing what you see.

.
 
gar said:
180224-2115 EST

DrSnowman:

Are you saying that you see a color difference, but your boss can not? If bulbs from two different manufactures are in the same fixture, then it should be easy to do a color and intensity comparison.

Your boss might have a color blindness that prevents him from seeing what you see.

.
Click to expand...

I agree, but also would think is possible to see noticable differences in same make/model if one is new and the other is already at half rated operating hours.
 
There is a color shift after lamps have been ran a while compared to new ones.
It seem from what I’ve experienced is that it tends to get warmer in color.
I know, one would think if something is given a rating it should be across the board.
 
180225-1009 EST

A K rating can only relate to a "black body" radiator where it has a unique definition. Anything else is an approximation.

.
 
DrSnowman said:
Appreciate all the input but I asked a very simple question...Do the colors of different brands of the same K rating fluorescent lamps match perfectly or are they slightly different? Almost all of the light fixtures in our buildings are Sylvania. The boss has been ordering GE equivalents because he can get them cheaper. But the colors don't appear to match all the time. I was hoping to get some of you to say yes or no so I could show him this thread and prove that there is a difference. I want him to order Sylvania.
Click to expand...

Yes
 
DrSnowman said:
Appreciate all the input but I asked a very simple question...Do the colors of different brands of the same K rating fluorescent lamps match perfectly or are they slightly different? Almost all of the light fixtures in our buildings are Sylvania. The boss has been ordering GE equivalents because he can get them cheaper. But the colors don't appear to match all the time. I was hoping to get some of you to say yes or no so I could show him this thread and prove that there is a difference. I want him to order Sylvania.
Click to expand...

Honestly, they look fine from my office. Maybe even his.
 
I've seen lay-in fixtures where the ones closer to a HVAC diffuser looked whiter due to the colder air blowing across the lamps.

So yes, it can be tough to get all the lamps to be the same color. You have a better chance by staying with the exact same brand and model number of lamp.

Also, I'm not sure, but I would suspect that if the color rendering index is different, that might also make the lamps look like a slightly different color. A 735 lamp may not look exactly the same as an 835, even though they are both supposed to be 3500K.
 
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