.

Generally those are called Daylight bulbs..you can find them at a HomeDepot type stores..good luck - generally the ones Ive seen though are the long skinny lamps..

My wife and I sell the LifeLite brand of full spectrum daylight bulbs which are rated at 6500K. They are compact fluorescents which screw into normal bulb sockets and have a ballast integrated into the base. We are considering carrying Lumiram products as well, and they have a full-spectrum incandescent bulb, but it's colour temp is lower. Our web site address is in my profile and you can contact me if you have any questions.

The bulbs sold as "daylight" bulbs in Home Depot are always lacking - either the colour temp is low, or the CRI (colour rendering index) is low, or they are not full spectrum (emitting no UVA or UVB).

I would like to get a normal screw in light bulb that's 6500K, and not a fluorescent......Does such a bulb exist?
To the best of my knowledge, no. All the screw-in base compact fluorescents I've see so far have poor color rendering. Color-critical industries recommend a minimum CRI of 90. Most CFLs don't even tell you the CRI because theirs is nothing to be proud of. The closest you will find in an incandescent is a 12 Volt MR16 at about 6000K, with excellent spectral power distribution (SPD), but it does not screw in. What are you trying to accomplish, simple reading?

Performance requirements depend on your application. If you truly want to mimic sunlight, you will have to use a metal halide type illuminant. They put out a lot of heat. The closest thing to sunlight in a fluorescent is GretagMacbeth's patented, 7-phosphor, D65, F20T12 tube. We use it filtered in our Ideal-Lume Pro video viewing environment luminaire.

One thing to keep in mind is, lots of claims are made in the lighting industry about color performance. Most are rough estimates at best. Many are outright false. I have measured many over the last 8 years in my lab. The over the counter stuff is particularly prone to using misleading claims.

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.

"Advancing the art and science of electronic imaging"

The LifeLite CFLs are 6500K with a CRI of 90. Their T8 tubes are 6000K with a CRI of 96. There is good product out there, and lots and lots of not so good! The good stuff doesn't come cheap though.

A 90 CRI compact fluorescent that screws into your lamp's bulb socket would do the trick. Why are you avoiding fluorescents?

Hmm, all the other LifeLite CFLs I've been able to find on the 'net have are rated at 5500K and 91 CRI. Why is there a difference in stated specs? Do they do limited runs of 6500K bulbs?

I'm not trying to rain on anyone's parade here, or cast aspersions. I'm just curious.

The product we normally carry is the LifeLite ECO and I don't believe this exact product is on their web site. It may even be exclusive to North America. The specs for the ECO are printed right on the packaging. However, even the product they have on their web site is rated at 6000K and a CRI of 95, so I'm not sure where you are getting your info from?

http://www.lifelite.de/english/vollspektrum_sparlampen.php

Hi, Johnny. This link is representative of what I found:

http://www.lightenergysource.com/LifeLiteLamps.htm#Spiral

Again, I'm not arguing or naysaying, just curious why the different specs.:o

My wife and I sell the LifeLite brand of full spectrum daylight bulbs which are rated at 6500K. They are compact fluorescents which screw into normal bulb sockets and have a ballast integrated into the base. We are considering carrying Lumiram products as well, and they have a full-spectrum incandescent bulb, but it's colour temp is lower. Our web site address is in my profile and you can contact me if you have any questions.

The bulbs sold as "daylight" bulbs in Home Depot are always lacking - either the colour temp is low, or the CRI (colour rendering index) is low, or they are not full spectrum (emitting no UVA or UVB).

What is the CRI of these bulbs that you sell?

edit: Sorry, I see the answer later in the thread. Do you have any spectral data? Anyone measure them independently?

Hey Royce...that's a different product! We carry the LifeLite brand from Life Energy Systems. This is "Life-Lite" from "Light Energy Source"!

There are lots of pretenders out there!

Leonard, there is spectral data as measured by the company on their website (which is replicated on ours), but I have no independent data. Their web site is http://www.lifelite.de/english/index.php

Are there any dealers in the US. I would buy a sample and measure the spectrum.

We cover the US and Canada. Email me and I'll set you up.

Lights of America makes a product called
Minisunlight. It's a 14W screw-in CFL.
854 lumen (60W light bulb equivalent)
6,000 hours
6500K
CRI 82

I use these in my bathroom. I got them in a four pack for $11.00 or so at Fred Meyer.

The DAYLIGHT GE brand sold at Wal-Mart is also 6,500K.

Fred Meyer also sells (a Kroger subsidary) OTT-LITE screw-in, however just like every other lamps marketed as "full spectrum", it's grossly over priced. $30 ea.

As for T8 lamps, among the best are:
Philips TL950, 5,000K CRI 98.
OSI Octron 950 5,000K CRI 90


Available from Home Depot:
Colortone 50 F40T12 5000K CRI 90 $11 for two pack, 4 foot.
Philips TL865 6500K CRI 85, 10 pack, $30

My wife and I sell the LifeLite brand of full spectrum daylight bulbs which are rated at 6500K. They are compact fluorescents which screw into normal bulb sockets and have a ballast integrated into the base. We are considering carrying Lumiram products as well, and they have a full-spectrum incandescent bulb, but it's colour temp is lower. Our web site address is in my profile and you can contact me if you have any questions.

The bulbs sold as "daylight" bulbs in Home Depot are always lacking - either the colour temp is low, or the CRI (colour rendering index) is low, or they are not full spectrum (emitting no UVA or UVB).

Define full spectrum. There's no industry defined standard for full specturm and it's marketing gimmick.
http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/fullSpectrum/disadvantages.asp

Hey, I just sell them. If you're not interested, don't buy.

With that said, marketing a "light bulb" and listing the specs as 6500K and CRI 92 probably won't get you very far since the vast majority of the population is completely unaware of the terms and meanings of such specifications.

Even the meaning of "High-Definition" can vary depending on who you ask and what industry you are applying it to. If I grab a dozen "high definition" Television sets, will they all have the same specs?

There is a visible difference with these bulbs, and a measurably broader spectrum - there's no doubt about that.

Hey, I just sell them. If you're not interested, don't buy.
You're missing the point. Other users may not realize that 6500K 82 CRI lamps from Home Depot will suite them just as well for a lot less. They can look at different sources for themselves and decide for themselves if they want.


Even the meaning of "High-Definition" can vary depending on who you ask and what industry you are applying it to. If I grab a dozen "high definition" Television sets, will they all have the same specs?

No, but when a TV set is sold as high-definition, you can be assured it will be able to receive at least one signal format that constitutes HDTV.

There is no lighting industry standard for "full spectrum"


There is a visible difference with these bulbs, and a measurably broader spectrum - there's no doubt about that.

That maybe so.
An old school, 63 CRI cool white 4100K has a measurably broader spectrum spread than a newer 85 CRI cool white too.

As far as "visible difference" difference is difference. Not bad or good and it's relative.

Compared to a 6500K Home Depot lamps, or standard light bulb?

There is no industry-wide definition for "full spectrum" but there are standards for "color rendering index (CRI)." Don't confuse the two terms. Industries that rely on consistent and accurate color judging under artificial lighting recommend a minimum CRI of 90.

They can look at different sources for themselves and decide for themselves if they want.
Not a good suggestion. Human vision is very sensitive but also very adaptable and easily fooled: http://www.avsforum.com/avs-vb/showthread.php?t=849430 . It cannot be relied on to judge color without an objective reference to compare something to.

How about GE's "Reveal" line? Those are the purplish-blue looking bulbs in every size and wattage and thread that exists in the home. I've heard recommendations for these bulbs to people who suffer from SAD - seasonal affective disorder - for months with shorter daylight.

I've measured these and they are no where near suitable for video bias lighting. The OP already ruled these out.

I've measured these and they are no where near suitable for video bias lighting.

What Kelvin did they measure?

Not a good suggestion. Human vision is very sensitive but also very adaptable and easily fooled: http://www.avsforum.com/avs-vb/showthread.php?t=849430 . It cannot be relied on to judge color without an objective reference to compare something to.

I believe I miss your point. If human vision is adaptable, then how many people are really going to notice degradation of an image when using a common 6500k 82CRI CFL screw-in bulb for a bias light? The reality is that most people probably have just typical lights in their room, so my general guess would be that if anything using something like a standard 6500k daylight bulb might be an improvement. I would be interested in a first-hand comparision with the 90+CRI bulbs, but a clearly different on-screen image would be necessary for me to consider a change due to the higher wattage and/or more inconvenient format of the higher CRI bulbs I've been able to find.

Without a first-hand comparison, by your comments here I'm confused how a higher CRI would really be beneficial. Yes the color items at http://www.echalk.co.uk/amusements/OpticalIllusions/illusions.htm are interesting, but I'm not sure they're exactly applicable as far as I can tell. I would have to guess that in the places I've watched video that the room environment might have an impact on perception regardless of the bulb. I don't get how with mostly reflected light the bulb would generally have a greater impact than the room. Odds are most people aren't necessarily going to care to change their environment like the color demonstrations might indicate as applicable.

http://www.hometheaterhifi.com/volume_11_2/ideal-lume-lighting-5-2004.html states "Image quality did not change, but the big difference was eye strain." Based on that I would tend to think that people could judge for themselves, of course understanding that their room is probably not color-neutral like in the review. If going from a dark room to a lighted room with a 6500k CFL bulb behind the TV doesn't cause a noticable shift in color then it would seem a reasonably cheap solution. Of course a further test could be to do a second off/on test with a higher CRI bulb, but of course if you can't find a noticable change with the first test then the second is irrelevant. I miss how doing a light-off/light-on test in an otherwise unlighted room wouldn't allow people to judge for themselves.

I believe I miss your point. If human vision is adaptable, then how many people are really going to notice degradation of an image when using a common 6500k 82CRI CFL screw-in bulb for a bias light? The reality is that most people probably have just typical lights in their room, so my general guess would be that if anything using something like a standard 6500k daylight bulb might be an improvement.
I have made it my business to advocate for well proven, long established, imaging industry standards and recommended practice. "Most people" are not concerned about image fidelity and artistic integrity in TV viewing. The masses are content with pictures that are 'good enough.' Most video consumers never make it to this forum. Those who do tend to regard a more detailed appraisal of what constitutes reference imaging.

"Nobody ever went broke underestimating the taste of the American public." H. L. Mencken

Cinematographers work very hard at achieving a certain mood or emotion in a scene through the oft times subtle manipulation of color and lighting. Telecine colorists transfer films to video using calibrated monitors, in neutral viewing environments, with D65 ambient lighting, under reference conditions, to preserve subtle color fidelity and artistic integrity. Frequently the cinematographer who worked on the original program will be present for the film's transfer to video in order to insure his vision is preserved. These viewing conditions are adhered to because they understand how fickle and adaptable the human visual system can be.

The information I have shared in this thread offers guidance for readers who value excellence in image reproduction. Ideal viewing conditions help to preserve image fidelity and artistic integrity in a home system. Some readers may feel the need to shave a few bucks off their equipment expenditure and settle for less than ideal performance. We're all entitled to our own set of priorities and compromises to the ideal. However, without an understanding of the ideal, how will one know what resulting consequences to evaluate?

You may speculate all you want about the relative impact of inferior CRI in a viewing environment lighting product. Personally, I try to avoid speculation, personal anecdotes, and general guessing when it comes to technical issues, especially when industry standards and proven recommended practice are available. Those who find value in personal anecdotes might be interested in this post submitted today:
http://www.avsforum.com/avs-vb/showthread.php?t=451527&goto=newpost . Be your own judge.

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.

"Advancing the art and science of electronic imaging"

I would like to understand your position, but from my own thoroughly practical perspective I don't get what you're attempting to convey. As I understand it, the ideal environment "to preserve subtle color fidelity" would be:

1) a color-controlled room
2) 6500k high CRI bulb for a bias light

My practical assertion was that many people don't have a dedicated theater room and are likely to have at least a somewhat tinted environment next to the display. I question how well does the ideal stand up in the real world when the environment is not very close to color-neutral? I question if the "well proven, long established, imaging industry standards and recommended practice" actually apply in a tinted environment with indirect light. The statement that "Industries that rely on consistent and accurate color judging under artificial lighting recommend a minimum CRI of 90" has me questioning, were those recommendations based on reflected light in environments that were not color-neutral? By my rudimentary understanding of physics, my "guessing" is that the color spectrum from the bulb would change as light is reflected off of a tinted surface. If that's at all accurate, then to what extent does CRI then matter? All of these are practical concerns, so I don't understand why your reply concerned ideals and a non-working personal anecdotes link.

My "speculation" was that by watching the display in an unlighted room the environment would have less impact on the perceived image. Basically I was presenting an unlighted room as the control situation. It seems every consumer display system probably already suffers from "less than ideal performance" (http://www.avsforum.com/avs-vb/showthread.php?p=12468022#post12468022), so I don't get why it wouldn't be reasonable to discuss this in objective terms and by individual observation to see how many people can personally notice changes and how many cannot. I had a hard time not simply writing off your prior reply as marketing.

So if someone watches in a dark room and then turns on and off a backlight to tell if they can perceive changes in color, what comments would you have about such a testing procedure? To me it seems an entirely practical way to test if a bulb is "no where near suitable for video bias lighting" by observing if you can personally notice a change in the image. Of course in a typically tinted environment it would seem to me that a higher CRI bulb might also fail this test for someone that could perceive changes. Anyway what I find interesting is engineering and this isn't my "business", so I thought it would be interesting to have some of my "general guessing" set straight if I was way off base.


To simplify all this into a few questions:

1) Has there been any testing which is directly applicable to the situation of reflected light in a typical bias light situation where the color in the room hasn't been specifically chosen?
2) If someone cannot observe changes in color by switching on and off a backlight, why would they then choose a more expensive higher CRI and higher wattage bulb?
3) Are you aware of any testing procedure, maybe along with a photographed image or video, that might allow a person to observe how an inferior CRI bulb can be a detriment "to preserve subtle color fidelity" with their display?

I fixed the post link. Sorry about that.

Of course, there's no end to the variety of viewing environment conditions found in residential systems. Rather than trying to sort out all hypotheticals, I prefer to comment on what works correctly. Hobbyists and design professionals can work backwards from that as they see fit.

Is there a viewing condition that could mask the subtle difference between an 84 CRI lamp and a 90 CRI lamp? Likely. I won't waste any further time focusing on what might happen. The closer one gets to the ideal, the better image performance will be. Following standards and recommended practice yields genuine benefits in the viewing experience.

The reason our consumer display systems are "less than ideal," and frankly always will be, is because perfection is a worthy target, not a realistic destination. You sound intelligent enough to understand that. It's my belief that losing sight of the ideal increases the likelihood and severity of compromise and the resulting consequences to performance. That's why I recommend 90 minimum CRI illuminants for bias lighting. Wall color is its own subject, neutral being best.

The original poster wanted ambient lighting in his theater to read by while viewing programming. He would be best served by a higher CRI than what might be marginally affordable from Home Depot, etc. Will he have to spend more? Likely. Would he be willing to make that compromise? That's up to him. Would he be able to tell a difference? That's too hypothetical.

1) Has there been any testing which is directly applicable to the situation of reflected light in a typical bias light situation where the color in the room hasn't been specifically chosen?
Not that I'm aware of. Please attempt your own experiments. I consider such an endeavor a complete waste of time and re-inventing the wheel.
2) If someone cannot observe changes in color by switching on and off a backlight, except by marketing, why would they then choose a more expensive higher CRI and higher wattage bulb?
The Society of Motion Picture and Television Engineers (SMPTE), the International Organization for Standardization (ISO), the International Telecommunications Union (ITU), etc., etc., are standards bodies who recommend D65 ambient lighting in neutral viewing environments for critical evaluation of color television pictures. They are not really concerned with marketing.

You may not like my answers to your questions, but that's all I think needs to be said about them. Please draw your own conclusions and go your own way.

There is no industry-wide definition for "full spectrum" but there are standards for "color rendering index (CRI)." Don't confuse the two terms. Industries that rely on consistent and accurate color judging under artificial lighting recommend a minimum CRI of 90.

Anything that strictly adheres to blackbody radiator curve is CRI 100, such as a standard incandescent lamp.


Not a good suggestion. Human vision is very sensitive but also very adaptable and easily fooled: http://www.avsforum.com/avs-vb/showthread.php?t=849430 . It cannot be relied on to judge color without an objective reference to compare something to.
I meant, sources, as in references. Not visually comparing.

CRI represent the way the light source renders the color of an object it lights up and not the way the light itself looks. That is the chromaticity.

"
Color of Illumination. The color of illumination can be described by two independent properties: chromaticity, or correlated color temperature (CCT), and color rendering. There is often confusion between chromaticity and color rendering. In simple terms, chromaticity refers to the color appearance of a light source, "warm" for low CCT values and "cool" for high CCT values. Color rendering refers to the ability of a light source, with its particular CCT, to render the colors of objects the same as a reference light source of the same CCT. This aspect is typically measured in terms of the CIE General Color Rendering Index. For more information see Chapter 4, Color. "(Guidelines for Acceptable Lighting, CH3, IESNA lighting handbook, IESNA.org)

JohnnyG was kind to send me a sample of the compact fluorescent he mentioned previously. I don't have the software installed in my computer to measure color rendering index (CRI), but I do have Colorfacts Professional and can measure most other characteristics of an illuminant's performance with my GretagMacbeth EyeOne meter. The pertinent ones for this section of the forum are compared below:

CIE 1931 2 degree chromaticity coordinates for D65: x 0.3127, y 0.3291.
Tolerances for broadcast monitor SMPTE C phosphors: +/- 0.005 x/y

The LifeLite Eco, 15 Watt compact fluorescent makes no CRI claims on the package but claims to be 6500K. It's correlated color temperature measures around 5800K. The chromaticity is at: x 0.3249. y 0.3545. That's a deviation of: x + 0.012, y + 0.025 from CIE D65. Its spectral power distribution shows a very prominent green spike and a prominent red spike that lead me to conclude the CRI is not anywhere near the 90 CRI JohnnyG reported.

For a comparative reference, here are the measurements I took at the same time of a random sample of the Ideal-Lume Standard. It's CCT came in at 6554K. The chromaticity was at: x 0.3117, y 0.3298. That's a deviation of: x - 0.001, y + 0.000. The spectral power distribution shows a prominent blue spike, which is as it should be.

These measurements for a consumer fluorescent product, that makes no official claims for superior CRI, follow a pattern I've encountered for years in the consumer lighting market. Don't assume accuracy in off-the-shelf consumer lighting products. I have learned to assume inaccuracy until proven otherwise, regardless of what the package says or doesn't say.

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.

"Advancing the art and science of electronic imaging"

Alan, how about you send me an Ideal-Lume now and I'll have it tested and post my results here too?

How about posting your testing methodology including how long the bulb was energized before taking readings?

I'll have to check with the manufacturer, but I wonder if the specs have been changed to this without updating the packaging as yet:

http://www.lifelite.ca/images/VS_Sparlampe.jpg

That would match your temperature reading of 5800K and does show at least a green spike at about 550nM.

I'll send you a sample for testing under the following conditions: I'll enclose your lamp with the Ideal-Lume Standard. Once you have measured both products with equivalent or better instrumentation, in equivalent lab conditions, you may publish your results in this thread, then return the Ideal-Lume Standard insured at your expense, or purchase it at original retail with shipping cost.

Test conditions:

Both lamps were energized for approximately 30 minutes prior to analysis.

Illumination was measured reflected off of an 8.5" x 11" Munsell N7 neutral gray reference (a Kodak 18% gray card would be accepted as an equivalent neutral reference)

Instrument was a GretagMacbeth EyeOne Beamer spectroradiometer, recently checked for accuracy against the following references: NIST-traceable Minolta CS-200 chroma meter; GretagMacbeth D65 F20T12-equipped Ideal-Lume Pro; AV Standards' TVS Pro optical comparator (calibrated by Joe Kane Products using a NIST-traceable PhotoResearch PR-650); and a Sony PVM96 D65 monochrome professional monitor.

Environmental conditions were a totally light controlled front projection theater in my office. Screen wall and all other walls are covered by very dark, nearly neutral colors, ceiling is flat black. Test bench was set up in the middle of the room and covered with black fabric.

Lamps were placed within 7" of the Munsell gray reference. Meter was placed within 10" of the reflecting surface. Your compact fluorescent was placed in a typical clamp style task lamp without a reflector. The Ideal-Lume Standard was randomly taken out of a box and used as it is sold, with the mechanical baffle tube in place, without the optional diffuser lens.

Last year, an independent research project in Australia, for evaluating projection screen materials, used an Ideal-Lume Standard as a reference illuminant. They used the same type of meter I own and came up with nearly identical readings from their Ideal-Lume as this recent session in my lab.

I will attempt to add the spectral power distribution graph to this post, from my measurements of the two lamps. If they don't show up, it's because I failed to get the image files to load successfully. Let me know if you still want me to send the light samples to you for your own testing.

Alan, I take issue with you asking me for a sample, then posting a negative review of the product while YOU MARKET A SIMILAR/COMPETING PRODUCT. I was an idiot for thinking you were doing this for personal and professional curiosity. I feel like I've been sucker-punched. I simply cannot imagine doing the same to you.

Now, with regard to your claimed results, why are you comparing a Compact Fluorescent BULB to a fluorescent TUBE? The specs for LifeEnergy's fluorescent tubes are superior to their CFLs. Have you even tested many CFLs? If you don't have the means to test CRI, how can you claim what the CRI is for your Ideal-Lume product?

Who manufacturers the tubes you use?

And just for the record, we sell these bulbs for general home lighting use...not specifically for home theater applications.

JohnnyG,

I understand why you would feel slighted by my taking advantage of your free sample to demonstrate the unreliability of lighting industry practices. My original intent was not to publish a negative review, but to determine if the product was worthy of use by my company. Had it performed as you described, I would be asking you to sign me up as a US dealer. I apologize and will reimburse you for the product and your shipping costs. Please supply that data and I'll send you a check.

I don't market my products for general home lighting use. This is the display calibration section of the forum. The originator of this thread was looking for technically accurate ambient lighting for his dedicated, front projection home theater, something that would not compromise the image on the screen. I concluded he would want to know if a solution recommended to him in the thread would not perform as advertised.

I have tested other CFLs and thus far none have performed well enough for my use. It would be wonderful if they would, since they can be used in the same type of lamp sockets as incandescents. Part of the problem is manufacturers' preoccupation with efficiency. They want maximum light output and formulate their phosphor mixes with a green boost in the spectrum. This is common across the board, both in the fluorescent lighting market and even TV manufacturing. They both sacrifice color accuracy for the sake of brightness.

The CRI ratings on my products have been supplied by their manufacturers. I requested a minimum CRI of 90 from the outfit that custom makes my T5 lamps for me. CRI is actually an inferior metric for demonstrating color performance when compared to spectral power distribution (SPD). Few consumers of lighting devices would sit still for an explanation of how to interpret an SPD graph or the equivalent data. CRI is an average, a single numeric value, so it's much simpler for consumers to comprehend and use for comparing the claimed performance of lamps. This is why it's used so much in the marketing of lights. Since I own a spectroradiometer I don't really need CRI figures for evaluating the performance of lighting devices.

old thread, but relevant to me.

My local Lowes now carries an Ottlite 25w CFL that is advertised as being 5500 K color temp. I'm using a home-made light meter with Avia fliters, and wonder if this bulb is close to being accurate for calibrating my meter.

Just looking for something close, for my entertainment (not pro calibration).

btw, using a random soft bulb, and the Sun as comparison, it seems to be in the ballpark.

Thanks

** http://www.ottlite.com/p-268-25-watt-compact-fluorescent-bulb.aspx

The lowes outer box advertises this bulb as 5500k, the only bulb in the entire store I found as 5500

old thread, but relevant to me.

My local Lowes now carries an Ottlite 25w CFL that is advertised as being 5500 K color temp. I'm using a home-made light meter with Avia fliters, and wonder if this bulb is close to being accurate for calibrating my meter.

Just looking for something close, for my entertainment (not pro calibration).

btw, using a random soft bulb, and the Sun as comparison, it seems to be in the ballpark.

Thanks

** http://www.ottlite.com/p-268-25-watt-compact-fluorescent-bulb.aspx


The lowes outer box advertises this bulb as 5500k, the only bulb in the entire store I found as 5500

what do you mean by that?

I am no expert on the subject but it has been talked about more than once here on the forum. The answer is NO. The value used for calibrations is D65 and that is not the same as 6500K. D65 is a particular mix of RGB. You can get 6500K with other mixes RGB that are not D65. Others will probably give you a better expatiation. Here is a video explanation... in the center of the video..
http://www.viddler.com/explore/hdnation/videos/69/

old thread, but relevant to me.

My local Lowes now carries an Ottlite 25w CFL that is advertised as being 5500 K color temp. I'm using a home-made light meter with Avia fliters, and wonder if this bulb is close to being accurate for calibrating my meter.

Just looking for something close, for my entertainment (not pro calibration).

btw, using a random soft bulb, and the Sun as comparison, it seems to be in the ballpark.

Thanks

** http://www.ottlite.com/p-268-25-watt-compact-fluorescent-bulb.aspx

The lowes outer box advertises this bulb as 5500k, the only bulb in the entire store I found as 5500
Is there a claim for color rendering index (CRI) on the package? I could not find claims listed for either correlated color temperature (CCT) or CRI on the linked web site. Tests that I have conducted over the years have demonstrated to me that claims made on consumer lighting packages/web sites are not reliable unless they provide very specific spectral data. Your comments indicate to me that your "calibration" methodology lacks enough precision to produce genuinely meaningful results for conventional display alignment. What is the point of settling on 5500K as a reference? Are you calibrating a digital photo/graphics monitor?

an HT projector, for fun. You don't need to be insulting. Is 5500k not the reference white level?

Is 5500k not the reference white level?

It should be the D65 white point, which corresponds to 6500K in terms of color temp.

an HT projector, for fun. You don't need to be insulting. Is 5500k not the reference white level?

Also for creating a tri-stimulus colorimeter you absolutely have to calibrate it with a spectroraidometer.

There are an infinite variety of spectrums that can create a color that would measure the same as D65 (D65 is actually defined with a spectral signature, not it's x,y coordinates). You need to have an accurate approximation of the spectral output of the light source you want to measure to create the correction matrix for the colorimeter.


Of course you can do anything for fun :)
Fun doesn't have any rules.

There are an infinite variety of spectrums that can create a color that would measure the same as D65 (D65 is actually defined with a spectral signature, not it's x,y coordinates).

Sotti, would you mind explaining this a little more. I am having a bit of difficulty in understanding this concept. Thanks.

Sotti, would you mind explaining this a little more. I am having a bit of difficulty in understanding this concept. Thanks.

I also have the same question.

So here is the spectral distribution of d65 (image from wikipedia).
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=235316&stc=1&d=1327551085

for the specific intensities, here is the official document from the CIE
http://www.cie.co.at/publ/abst/datatables15_2004/std65.txt

When measuring colors we take the spectrum and apply a color matching function against them to get XYZ values (colorimeters shortcut this process by trying to emulate the Color matching function with their filters). Those XYZ values we then convert to x,y values to plot in 2D. The Y from XYZ is what we use for luminance.

So here is a Dell u2410 IPS panel calibrated to 0.3128, 0.329
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=235317&stc=1&d=1327552038

Here is a Dell 2408wfp PVA panel calibrated to 0.3129, 0.329
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=235318&stc=1&d=1327552038

While similar they are significantly different. I mentioned above color matching functions, the way they work is that the area of the spectrum under each curve is summed up so the area under the X curve is the X value, Y, Z ect...

Here is the 2408, with the standard 1931 2 degree colormatching function laid ontop.
http://www.avsforum.com/avs-vb/attachment.php?attachmentid=235319&stc=1&d=1327552038

So as long as the areas match your eye SHOULD see the same "color". But the Color matching functions are just approximations but everyones eyes are a little bit different, so you would notice a difference if the spectrums are significantly different.