Are there any screw in regular light bulbs that give off 6500k white light? - Page 2 - AVS Forum
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Old 03-17-2008, 02:18 PM
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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.
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Old 03-17-2008, 02:42 PM
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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.
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Old 03-17-2008, 04:48 PM
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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.
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Old 01-25-2012, 11:15 AM
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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...cent-bulb.aspx

The lowes outer box advertises this bulb as 5500k, the only bulb in the entire store I found as 5500
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Old 01-25-2012, 11:19 AM
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Quote:
Originally Posted by y2khardtop View Post

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...cent-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?
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Old 01-25-2012, 11:29 AM
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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/
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Old 01-25-2012, 11:50 AM
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Quote:
Originally Posted by y2khardtop View Post

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...cent-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?
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Old 01-25-2012, 04:18 PM
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an HT projector, for fun. You don't need to be insulting. Is 5500k not the reference white level?
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Old 01-25-2012, 04:20 PM
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Quote:
Originally Posted by y2khardtop View Post

Is 5500k not the reference white level?

It should be the D65 white point, which corresponds to 6500K in terms of color temp.
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Old 01-25-2012, 04:30 PM
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Quote:
Originally Posted by y2khardtop View Post

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.

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Old 01-25-2012, 07:57 PM
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Originally Posted by sotti View Post

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.
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Old 01-25-2012, 09:13 PM
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Quote:
Originally Posted by Razz1 View Post

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.
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Old 01-25-2012, 09:31 PM
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So here is the spectral distribution of d65 (image from wikipedia).


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


Here is a Dell 2408wfp PVA panel calibrated to 0.3129, 0.329


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.


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.
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