Is this a cheap alternative to the "Ideal lume"? - AVS Forum
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post #1 of 43 Old 06-24-2011, 08:22 PM - Thread Starter
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after extensive searching , I am considering buying the Sun Blaze T5 Fluorescent Single Strip Grow Light 2ft 24W 6500K to use as a bias light for my KDL-52XBR6 (52 inch sony LCD):

http://www.specialty-lights.com/960315.html

It appears to have everything one needs in a bias light? Electronic ballast, 6500k, with a CRI of 85 (listed in the details) :

http://www.specialty-lights.com/901586.html


is there anything i may have missed (in comparing the two) before i pull the trigger on this?

seems like its not that much different than the ideal lume, or is there something I missed?

24 watts, 2000 lumens, will that be too bright (for a 52 inch LCD, one foot away from the wall)? I know i can just use aluminum foil to hide some of the light if so, as mentioned in this article...
so i guess too bright is better than too dim?

if not the sunblaze, then what about :

http://reviews.cnet.com/4520-11247_7...content;rb_mtx

from the article (cnet):

"You can pick up a 6,500K light from Home Depot, Lowe's, or Sears. Look for one of the following items:"

Westinghouse 18-inch 6,500K 94CRI 15w T-8
Philips Daylight F20T12/D
Westinghouse F15T8/FS 18-inch 6,500K 48CRI

i believe those three bulbs would cost about 7 dollars a piece.

any thoughts? I wouldnt expect the sunblaze to be as good or better than the ideal lume, after all its made for growing plants or herbs ??!
is it decent enough tho?
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post #2 of 43 Old 06-24-2011, 08:54 PM
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I would suggest a bulb that that a higher CRI.. i.e. less color

David

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post #3 of 43 Old 06-24-2011, 09:00 PM - Thread Starter
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Originally Posted by rovingtravler View Post

I would suggest a bulb that that a higher CRI.. i.e. less color

hmm, there's a lot of difference between 84 CRI (sunblaze) and 90 (ideal lume standard) CRI?
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post #4 of 43 Old 06-25-2011, 01:01 AM
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It's going to be crap, but you'll probably never notice so what the hell.

6500K tells you almost nothing about how much or little green light is in the source. 6500K is influenced about 85%-90% by the amount of blue and red/yellow in the light. You can have WAY WAY WAY too much (or too little) green and it can still measure 6500K. Green errors are the most obvious errors also and will most easily throw your color off.

You have 2 choices... do it cheap or do it right.

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post #5 of 43 Old 06-25-2011, 05:52 AM - Thread Starter
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Quote:
Originally Posted by Doug Blackburn View Post

It's going to be crap, but you'll probably never notice so what the hell.

6500K tells you almost nothing about how much or little green light is in the source. 6500K is influenced about 85%-90% by the amount of blue and red/yellow in the light. You can have WAY WAY WAY too much (or too little) green and it can still measure 6500K. Green errors are the most obvious errors also and will most easily throw your color off.

You have 2 choices... do it cheap or do it right.


so there is no way to tell what kind of bulb you are buying? say i go to home depot and buy a philips daylight 6500k bulb with 75 CRI, its going to be wrong?


the CNET article i liked above mentions these 3 bulbs:

"Ratings of 5,000K and higher are referenced to daylight, based on different times of the day; 6,500K is best for a home-theater application. A white light rated at 6,500K will exactly match the white on a correctly calibrated TV set. You can pick up a 6,500K light from Home Depot, Lowe's, or Sears. Look for one of the following items:"

Westinghouse 18-inch 6,500K 94CRI 15w T-8
Philips Daylight F20T12/D
Westinghouse F15T8/FS 18-inch 6,500K 48CRI

are you saying that the first bulb, a 6500k with 94 CRI is going to be crap too?
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post #6 of 43 Old 06-25-2011, 08:22 AM
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Have you heard of SAD lights? Seasonal affective disorder. They use CRI 94 or higher I have a desk lamp that is 98 and the difference is amazing. I have actually checked the color temp which is you can set, three setting warm, normal, cool; and they are about 8000K, 6500, and 5500. I had a different light prior that was only CRI90 and the difference was clear.

I have no experience with Ideal Lume, but I would hope they actually do some testing.

Doug is saying buy the real thing that might be tested and or designed for the right job.

David

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post #7 of 43 Old 06-25-2011, 09:49 AM
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Quote:
Originally Posted by mikediamond View Post

after extensive searching , I am considering buying the Sun Blaze T5 Fluorescent Single Strip Grow Light 2ft 24W 6500K to use as a bias light for my KDL-52XBR6 (52 inch sony LCD):

http://www.specialty-lights.com/960315.html

It appears to have everything one needs in a bias light? Electronic ballast, 6500k, with a CRI of 85 (listed in the details) :

http://www.specialty-lights.com/901586.html


is there anything i may have missed (in comparing the two) before i pull the trigger on this?

seems like its not that much different than the ideal lume, or is there something I missed?...

Mike,

My recommendation is to go with the Ideal-Lume. It's designed for use in home theater systems (I don't believe the "Grow Lights" are), it's high quality - and you get an extra bulb. I recommend the Ideal-Lume lights to MANY of my clients, and they are very happy with them.

I don't think you'll find a better VALUE than the Ideal-Lume (but you might find things that are cheaper).

Hope that helps....

Best,
Greg

All High Def LLC

ISF Certified
THX Certified Professional Video Calibration
THX Certified Professional Home Theater 2
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post #8 of 43 Old 06-25-2011, 02:07 PM
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The walls reflecting that bias light have to be D65 for the D65 light to matter. I remember reading that the eyes are bias 80% by the display, 20% by the surround, so the display will also need to be calibrated D65 accurate for it to matter much what the surround color is. Most of the benefit of a bias light is due to there being diffuse light in your field of view as well as the image so increasing perceived contrast, you would get that benefit D65 or not.

CinemaQuests ideal lume pro uses a GretagMacbeth lamp that meets the relevant industry standards, it uses a patented seven phosphor formulation to meet the Spectral Power Distribution SPD requirements, the lamp is used for bias lighting in critical applications in the video industry. You could just buy the lamp from CinemaQuest for $23.95 or if you do not like CinemaQuest from a different seller.

The ideal lume standard is for home use, it uses a normal three phosphor lamp. Both Correlated Color Temperature rating and Color Rendering Index are considered average measurements or approximations. CinemaQuest did not used to test the CRI rating, they just went by what the manufacture claimed, do not know if they now test them. They have tested the color temperature in the past on samples and claimed typical results 6500 +/-500K, with some samples outside that. They claim the Spectral Power Distribution SPD is excellent but it is a three phosphor lamp. BeachComber in the past tested ideal lume standard and was not impressed he found the color temperature dropped over time down to below 6000K after 500 hours use, he also found cheaper lamps that gave better results. SMPTE RP166-5.3 states "The reflective surround should be illuminated with a light quality closely matching illuminant D65." no tolerance range is given and no mention of SPD so ideal lume standard is sold as bias lighting solution for home use, it does not meet industry standards for critical use.

A old thread on bias lighting and ideal lume.
http://www.avsforum.com/avs-vb/showthread.php?t=451527
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post #9 of 43 Old 06-25-2011, 02:15 PM - Thread Starter
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Quote:
Originally Posted by dovercat View Post

The walls reflecting that bias light have to be D65 for the D65 light to matter. I remember reading that the eyes are bias 80% by the display, 20% by the surround, so the display will also need to be calibrated D65 accurate for it to matter much what the surround color is. Most of the benefit of a bias light is due to there being diffuse light in your field of view as well as the image so increasing perceived contrast, you would get that benefit D65 or not.

CinemaQuests ideal lume pro uses a GretagMacbeth lamp that meets the relevant industry standards, it uses a patented seven phosphor formula, and is what the industry use for bias lighting in critical applications. You could just buy the lamp from CinemaQuest for $23.95

The ideal lume standard on the other hand is for home use. Both Correlated Color Temperature rating and CRI Color Rendering Index are considered average or approximations. They do not test the CRI rating, they just go by what the manufacture claims. They have tested the color temperature in the past and get results typically 6500 +/-500K, with some samples outside that. BeachComber in the past tested ideal lume standard and was not impressed he found the color temperature dropped over time down to below 6000K after 500 hours use, he also found cheaper lamps that gave better results. SMPTE RP166-5.3 states "The reflective surround should be illuminated with a light quality closely matching illuminant D65." no tolerance range is given so ideal lume standard is sold as bias lighting solution for home use not industry critical use.

A old thread on bias lighting and ideal lume.
http://www.avsforum.com/avs-vb/showthread.php?t=451527

hmmm so if i just buy the lamp (fluorescent bulb) from Ideal Lume website, I can just fit it in any fixture that fits it? (i would get an electronic ballast of course), but that seems like it would work out to much cheaper than buying the full kit?
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post #10 of 43 Old 06-26-2011, 12:00 PM
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First off, there's no such thing as D65... it's d65... always.

And as I said in the initial post 6500K means almost nothing because an excess or shortage of green, even in very large amounts can still measure 6500K. For the ultimate in bias lighting, you want the surroundings (everything around the video display and the reflected light from the bias light) to be neutral... neutral gray works well. The WORST case for bias lighting would be a room with green walls... the properly balanced bias light would bounce off the green paint ruining the balance of the bias light in the worst possible way. That's why you want neutral gray or very very muted color around the bias light area and around the TV's environment.

Next, they can print any damn number on the package they want to print. It is almost meaningless. How are you going to know which package or brand is reporting specs accurately. Is there a tolerance listed on the package? Probably not. And if their tolerance is +/- 50% they sure aren't going to tell you. And you can be CERTAIN that the tolerance on mass produced lamps is going to be HUGE. If you've never seen a manufacturer stretch the truth in product labeling, you either aren't paying attention or are very naieve.

Ideal-Lume lamps are made to simulate d65 light sources... d65 is very specific about the balance of red, green, and blue. Typical fluorescents have just a few chemicals in the coating that control the spectrum of the light the lamp emits. Ideal-Lume fluorescents have a unique chemical makeup with 7 or 8 chemicals in the light emitting coating that insure proper (neutral) color balance. You can't get this level of attention to proper light spectrum in any other lamp that's suitable for bias lighting.

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post #11 of 43 Old 06-26-2011, 12:25 PM - Thread Starter
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Quote:
Originally Posted by Doug Blackburn View Post

First off, there's no such thing as D65... it's d65... always.

And as I said in the initial post 6500K means almost nothing because an excess or shortage of green, even in very large amounts can still measure 6500K. For the ultimate in bias lighting, you want the surroundings (everything around the video display and the reflected light from the bias light) to be neutral... neutral gray works well. The WORST case for bias lighting would be a room with green walls... the properly balanced bias light would bounce off the green paint ruining the balance of the bias light in the worst possible way. That's why you want neutral gray or very very muted color around the bias light area and around the TV's environment.

Next, they can print any damn number on the package they want to print. It is almost meaningless. How are you going to know which package or brand is reporting specs accurately. Is there a tolerance listed on the package? Probably not. And if their tolerance is +/- 50% they sure aren't going to tell you. And you can be CERTAIN that the tolerance on mass produced lamps is going to be HUGE. If you've never seen a manufacturer stretch the truth in product labeling, you either aren't paying attention or are very naieve.

Ideal-Lume lamps are made to simulate d65 light sources... d65 is very specific about the balance of red, green, and blue. Typical fluorescents have just a few chemicals in the coating that control the spectrum of the light the lamp emits. Ideal-Lume fluorescents have a unique chemical makeup with 7 or 8 chemicals in the light emitting coating that insure proper (neutral) color balance. You can't get this level of attention to proper light spectrum in any other lamp that's suitable for bias lighting.

and how does the C.R.I. number play into this?
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post #12 of 43 Old 06-26-2011, 01:15 PM
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Quote:
Originally Posted by Doug Blackburn View Post

First off, there's no such thing as D65... it's d65... always.

Blame wikipedia "Illuminant D65"
Xrite Understanding Illuminants who manufacture the lamp used in the ideal lume pro and use the term "Illuminant D65"
http://www.xrite.com/documents/apps/...s/Ca00002a.pdf
CinemaQuest who sell the ideal lume and use the term "Ambient lighting should be of the correct color, as close as possible to CIE D65 (D6500 Kelvins)"
Since I am in the UK also blame the European Broadcast Union, EBU Tech3320 User requirements for Video Monitors in Television Production who use the term "reference white colour D65"

Quote:
Originally Posted by Doug Blackburn View Post

Ideal-Lume lamps are made to simulate d65 light sources... d65 is very specific about the balance of red, green, and blue. Typical fluorescents have just a few chemicals in the coating that control the spectrum of the light the lamp emits. Ideal-Lume fluorescents have a unique chemical makeup with 7 or 8 chemicals in the light emitting coating that insure proper (neutral) color balance. You can't get this level of attention to proper light spectrum in any other lamp that's suitable for bias lighting.

Ideal lume lamps are not unique and are not ideal lume lamps, ideal lume does not manufacture lamps.

The lamp supplied with ideal lume pro is a GretagMacbeth (now X-Rite) patented 7-phosphor mix lamp that meets industry standards to be used as a bias light.

The lamp supplied with ideal lume standard is a normal 3-phosphor mix lamp that fails to meet industry standards and it is sold for home use.
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post #13 of 43 Old 06-26-2011, 03:52 PM
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Quote:
Originally Posted by dovercat View Post

The walls reflecting that bias light have to be D65 for the D65 light to matter. I remember reading that the eyes are bias 80% by the display, 20% by the surround, so the display will also need to be calibrated D65 accurate for it to matter much what the surround color is. Most of the benefit of a bias light is due to there being diffuse light in your field of view as well as the image so increasing perceived contrast, you would get that benefit D65 or not.

CinemaQuests ideal lume pro uses a GretagMacbeth lamp that meets the relevant industry standards, it uses a patented seven phosphor formulation to meet the Spectral Power Distribution SPD requirements, the lamp is used for bias lighting in critical applications in the video industry. You could just buy the lamp from CinemaQuest for $23.95 or if you do not like CinemaQuest from a different seller.

The ideal lume standard is for home use, it uses a normal three phosphor lamp. Both Correlated Color Temperature rating and Color Rendering Index are considered average measurements or approximations. CinemaQuest did not used to test the CRI rating, they just went by what the manufacture claimed, do not know if they now test them. They have tested the color temperature in the past on samples and claimed typical results 6500 +/-500K, with some samples outside that. They claim the Spectral Power Distribution SPD is excellent but it is a three phosphor lamp. BeachComber in the past tested ideal lume standard and was not impressed he found the color temperature dropped over time down to below 6000K after 500 hours use, he also found cheaper lamps that gave better results. SMPTE RP166-5.3 states "The reflective surround should be illuminated with a light quality closely matching illuminant D65." no tolerance range is given and no mention of SPD so ideal lume standard is sold as bias lighting solution for home use, it does not meet industry standards for critical use.

A old thread on bias lighting and ideal lume.
http://www.avsforum.com/avs-vb/showthread.php?t=451527

There is no such thing as a D65(d65) wall or color of gray. The color should be as neutral as possible for best results. True neutral gray (includes white) will reflect light without altering its spectral composition. We are quite clear in all of our literature about the benefits of providing a neutral wall behind the display.

The primary benefit of correct ambient lighting addressed in the SMPTE RP166 document is to preserve correct color perception for the viewer. This is abundantly clear if the document is followed throughout its full context.

The Ideal-Lume Standard and Panelight models were developed for consumer use. However, many professional users have acquired these models for less critical applications and we get repeat orders regularly from companies such as: Technicolor, Dolby Labs, Blizzard Entertainment (Activision/Vivendi), The Moving Picture Company, etc.

Our claim of "excellent" SPD is in the context of fluorescents with lower CRI ratings or incandescents. Daylight simulator fluorescent lamps with CRI ratings of 90 or higher are preferred and recommended for industry applications where more reliable color comparison of surfaces is desired.

BeachComber's tests revealed nothing out of the ordinary. All phosphors age at different rates. Even the GretagMacbeth D65 lamp drops in the blue part of the spectrum upon warm up and drifts "minus blue" over longer periods of time. The drift is more significant when new, then it tends to stabilize as it matures. Phosphor based displays also drift with age, most notably blue. His comparisons to the Ideal-Lume 90 CRI T5 lamp were fundamentally flawed in that he compared it to 98 CRI T8 samples. He also did not note their behavior over as long a period of use, as I recall. We used to offer T8 fixtures and still offer 98 CRI T8 lamps comparable to the ones he referenced. However, we had problems sourcing reliable and suitable T8 fixtures, resulting in the switch to the much more slender T5 technology. We made the switch in order to accommodate the growing number of owners of wall mounted flat panels, who needed something that could fit behind such displays.

The old bias lighting thread was locked before I could respond to BeachComber's assertions. Then it was replaced with the simplified, less tedious, and non-combative current thread in the 'Links to this forums [sic] popular threads' collection of stickies at the top of this sub section of the forum: 'D65 Video Bias Lighting- Fundamental Theory And Practice' .

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.
A Lion AV Consultants Affiliate

"Advancing the art and science of electronic imaging"
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post #14 of 43 Old 06-26-2011, 06:03 PM - Thread Starter
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Quote:
Originally Posted by GeorgeAB View Post

There is no such thing as a D65(d65) wall or color of gray. The color should be as neutral as possible for best results. True neutral gray (includes white) will reflect light without altering its spectral composition. We are quite clear in all of our literature about the benefits of providing a neutral wall behind the display.

The primary benefit of correct ambient lighting addressed in the SMPTE RP166 document is to preserve correct color perception for the viewer. This is abundantly clear if the document is followed throughout its full context.

The Ideal-Lume Standard and Panelight models were developed for consumer use. However, many professional users have acquired these models for less critical applications and we get repeat orders regularly from companies such as: Technicolor, Dolby Labs, Blizzard Entertainment (Activision/Vivendi), The Moving Picture Company, etc.

Our claim of "excellent" SPD is in the context of fluorescents with lower CRI ratings or incandescents. Daylight simulator fluorescent lamps with CRI ratings of 90 or higher are preferred and recommended for industry applications where more reliable color comparison of surfaces is desired.

BeachComber's tests revealed nothing out of the ordinary. All phosphors age at different rates. Even the GretagMacbeth D65 lamp drops in the blue part of the spectrum upon warm up and drifts "minus blue" over longer periods of time. The drift is more significant when new, then it tends to stabilize as it matures. Phosphor based displays also drift with age, most notably blue. His comparisons to the Ideal-Lume 90 CRI T5 lamp were fundamentally flawed in that he compared them to 98 CRI T8 samples. He also did not note their behavior over as long a period of use, as I recall. We used to offer T8 fixtures and still offer 98 CRI T8 lamps comparable to the ones he referenced. However, we had problems sourcing reliable and suitable T8 fixtures, resulting in the switch to the much more slender T5 technology. We made the switch in order to accommodate the growing number of owners of wall mounted flat panels, who needed something that could fit behind such displays.

The old bias lighting thread was locked before I could respond to BeachComber's assertions. Then it was replaced with the simplified, less tedious, and non-combative current thread in the 'Links to this forums [sic] popular threads' collection of stickies at the top of this sub section of the forum: 'D65 Video Bias Lighting- Fundamental Theory And Practice' .

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.
A Lion AV Consultants Affiliate

"Advancing the art and science of electronic imaging"


so GeorgeAB if i have my own T5 or T8 fixture, would it be fine to just order your bulb?
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post #15 of 43 Old 06-26-2011, 06:16 PM
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SMPTE RP166-5.3 says "The reflective surround should be illuminated with a light quality closely matching illuminant D65." Illuminate D65 is defined by the International Commission on Illumination, CIE Technical Report (1999) A Method for Assessing the Quality of Daylight Simulators for Colorimetry, and its supplements. Spectral Power Distribution is a key factor in how good the daylight simulator is just as Doug Blackburn pointed out, that is why the lamp designed to be used as a D65 bias light uses 7-phosphors. Considering you sell 7-phosphor lamps designed to be used as D65 illuminates for $23.95 why someone would instead buy a 3-phosphor $12.95 lamp is beyond me.

It is all very well people dismissing cheaper alternatives to the ideal lume standard by saying 6500K and CRI are meaningless but those are the only claims CinemaQuest website makes for the ideal lume standard.
That it is 6500K and as you have previously posted that is a typical figure that changes overtime, 6500K as Doug Blackburn pointed out is a useless spec. That it has a CRI of 90, which as you have previously posted is a average or approximation, CRI alone as guides on evaluating the quality of an illumination setup for printing point out is useless. That it has excellent SPD which as you have posted is in context of fluorescent lamps with lower CRI ratings or incandescent lamps.

The CIE have defined methods for evaluating D65 Illuminates so how does the ideal lume standard measure up using the methods for evaluating D65 Illuminates.

On the CinemaQuest website you have a theoretical SPD graph for CIE D65 illuminate and a actual SPD graph for the ideal lume pro what about one for the ideal lume standard using 5nm or 10nm resolution. I thought the old thread was quite interesting because BeachComber did just that http://www.avsforum.com/avs-vb/showt...2#post15766832. Other companies selling D65 lamps for use in color matching have SPD graphs on their websites.
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post #17 of 43 Old 06-26-2011, 07:51 PM - Thread Starter
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Quote:
Originally Posted by dovercat View Post

SMPTE RP166-5.3 says "The reflective surround should be illuminated with a light quality closely matching illuminant D65." Illuminate D65 is defined by the International Commission on Illumination, CIE Technical Report (1999) A Method for Assessing the Quality of Daylight Simulators for Colorimetry, and its supplements. Spectral Power Distribution is a key factor in how good the daylight simulator is just as Doug Blackburn pointed out, that is why the lamp designed to be used as a D65 bias light uses 7-phosphors. Considering you sell 7-phosphor lamps designed to be used as D65 illuminates for $23.95 why someone would instead buy a 3-phosphor $12.95 lamp is beyond me.

It is all very well people dismissing cheaper alternatives to the ideal lume standard by saying 6500K and CRI are meaningless but those are the only claims CinemaQuest website makes for the ideal lume standard.
That it is 6500K and as you have previously posted that is a typical figure that changes overtime, 6500K as Doug Blackburn pointed out is a useless spec. That it has a CRI of 90, which as you have previously posted is a average or approximation, CRI alone as guides on evaluating the quality of an illumination setup for printing point out is useless. That it has excellent SPD which as you have posted is in context of fluorescent lamps with lower CRI ratings or incandescent lamps.

The CIE have defined methods for evaluating D65 Illuminates so how does the ideal lume standard measure up using the methods for evaluating D65 Illuminates.

On the CinemaQuest website you have a theoretical SPD graph for CIE D65 illuminate and a actual SPD graph for the ideal lume pro what about one for the ideal lume standard using 5nm or 10nm resolution. I thought the old thread was quite interesting because BeachComber did just that http://www.avsforum.com/avs-vb/showt...2#post15766832. Other companies selling D65 lamps for use in color matching have SPD graphs on their websites.

agreed , i somehow doubt that a bulb manufactured by Philips or Westinghouse, like the author of C-net article recommends (Westinghouse 18-inch 6,500K 94CRI 15w T-8), which indicates 6500k and 94 CRI is going to be completely useless as a bias light ....
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post #18 of 43 Old 06-27-2011, 06:58 AM
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Greetings

IT's cheap ... try it out ... can't hurt. You just need to figure out a way to modulate the light output from the bulb as it is normally way way too bright.

You will need to reduce the output by more than 70% ...

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post #19 of 43 Old 06-27-2011, 08:30 AM
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A 12" 8 watt tube would put out less light, though I don't know if there's a 6500K bulb available in that size.
Did we find out what color your wall is behind and around the TV?
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post #20 of 43 Old 06-27-2011, 09:11 AM
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Originally Posted by Michael TLV View Post

Greetings

IT's cheap ... try it out ... can't hurt. You just need to figure out a way to modulate the light output from the bulb as it is normally way way too bright.

You will need to reduce the output by more than 70% ...

regards

I just used tin foil to reduce the light output when I was trying out bias lighting.

How bright should the bias lighting be?

According to Joe Kane DVE test disc reference for maximum ambient light test pattern and guide the maximum surround brightness should be 10% of the peak white. CinemaQuest also say "SMPTE recommends the level (brightness) of ambient lighting should be no greater than 10% of the brightest white produced in the video image on the display"

SMPTE RP166 recommends a white level of 120 nits (35fL) with an ambient light level <12 nits (<3.5fL) so max 10%. But I have read in practice they use similar white levels to those use in Europe EBU TECH 3320 version 2 Oct 2010, 70 to at least 100cd/m2 (20.43-29.19+fL) white, the old EBU TECH 3320 version 1.1 May 2008 used 80cd/m2 (23.35fL) as an example of a reference white point. So that would be 17-12% with 15% as the example. EBU TECH 3320 states "If the viewing conditions are standard dim surround (15% as in ITU-R Rec. BT.500-11)" ITU-R BT.500-11 Methodology for the subjective assessment of the quality of television pictures is "Ratio of luminance of background behind picture monitor to peak luminance of picture:~0.15"

So max 10% according to the SMPTE standard, maybe 12-17% using the EBU white level and possibly 15% in practice and according to the ITU.
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post #21 of 43 Old 06-27-2011, 09:41 AM
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Originally Posted by mikediamond View Post

and how does the C.R.I. number play into this?

I have no idea. In 34 years of working with imaging systems at Eastman Kodak Company and getting into image analysis as an understudy to image scientists, I never heard of CRI until it came up with light bulbs and tubes. Who measures CRI? Is the room the lamps are measured in black or neutral gray? What instrument is used? Is it a spectroradiometer that is accurate regardless of the spectrum or is it a filter-based meter that would be heavily influenced by spectrum? How often are they calibrating their meter? How many lamps are measured (all of them? 1 out of 100?, 1 out of 1000?, one prototype and never any production lamp?)? Again, what is the tolerance (probably never stated)? What source are they using as a reference to insure their meter is accurate?

And... perhaps most important for bias lighting purposes, what is the SPECTRUM of the light? A single number like "CRI" can't tell you anything about the spectral content. d65 tells you about the proportions of red, green, and blue but even THAT doesn't tell you anything about spectrum. Ideally, you want the SPECTRUM of the bias light to be equivalent to the spectrum of red, green, and blue light produced by the TV.

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post #22 of 43 Old 06-27-2011, 09:42 AM - Thread Starter
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Originally Posted by Chad B View Post

A 12" 8 watt tube would put out less light, though I don't know if there's a 6500K bulb available in that size.
Did we find out what color your wall is behind and around the TV?


my wall is covered with a wallpaper that has a vertical green/grey stripe every 2 inches, with off white in between (the majority of the wall is off white, with a greyish green stripe every 2 inches), what effect does vertical stripes have on bias lighting?
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post #23 of 43 Old 06-27-2011, 09:53 AM
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Originally Posted by dovercat View Post

Blame wikipedia "Illuminant D65"
Xrite Understanding Illuminants who manufacture the lamp used in the ideal lume pro and use the term "Illuminant D65"
http://www.xrite.com/documents/apps/...s/Ca00002a.pdf
CinemaQuest who sell the ideal lume and use the term "Ambient lighting should be of the correct color, as close as possible to CIE D65 (D6500 Kelvins)"
Since I am in the UK also blame the European Broadcast Union, EBU Tech3320 User requirements for Video Monitors in Television Production who use the term "reference white colour D65"

Not only is there no such thing as D65, there's also no such thing as D6500 (with or without "Kelvins" after it). And even "Kelvins" is wrong as much as "Fahrenheits" or "Celsiuses" is wrong.

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post #24 of 43 Old 06-27-2011, 01:44 PM
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Originally Posted by mikediamond View Post
my wall is covered with a wallpaper that has a vertical green/grey stripe every 6 inches, with off white in between (the majority of the wall is off white, with a greyish green stripe every 6 inches), what effect does vertical stripes have on bias lighting?
Not necessarily the stripes; any non neutral color will negate at least some of the advantages of getting a color correct backlight.
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post #25 of 43 Old 06-27-2011, 02:04 PM - Thread Starter
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Not necessarily the stripes; any non neutral color will negate at least some of the advantages of getting a color correct backlight.

yeah i meant vertical grey/green stripes (every 2 inches!) not just any stripes
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post #26 of 43 Old 06-28-2011, 01:58 PM
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so there is no way to tell what kind of bulb you are buying?
CIE x, y color coordinates will tell you how close the bulb is to D65. You may have to dig for that info though (if it's available at all).

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Originally Posted by mikediamond View Post
and how does the C.R.I. number play into this?
A high CRI may be desireable as well in terms of the appearance of objects around the display, but for the record it has nothing to do with how close a light source is in color to D65. All it tells you is how well the bulb "renders" colors compared to a natural or continuous spectrum source. So it has more to do with the bulb's SPD. From Wikipedia...

Quote:
The CRI of a light source does not indicate the apparent color of the light source; that information is under the rubric of the correlated color temperature (CCT).
3000K, 4100K, 5000K, etc. bulbs are all capable of achieving high CRI ratings if they display colors well.

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post #27 of 43 Old 06-28-2011, 02:13 PM
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Originally Posted by Michael TLV View Post
You just need to figure out a way to modulate the light output from the bulb as it is normally way way too bright.

You will need to reduce the output by more than 70% ...

regards
Good point!!

Those 2000 lumen grow lights will be way too bright to be useful as a bias light. Depending on your lighting arrangement, you probably won't want something much brighter than about 200 lumens (roughly the light output of a 25-watt incandescent bulb), and may want something as low as 50 - 100 lumens if you have very bright walls, and excellent black levels on your display.

Edit: ^This would be supplemental to other room lighting btw.

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post #28 of 43 Old 06-28-2011, 02:19 PM - Thread Starter
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Good point!!

Those 2000 lumen grow lights will be way too bright to be useful as a bias light. You will probably want something more in the 50 to 150 lumen range.
any idea how many lumens the ideal lume standard puts out?
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post #29 of 43 Old 06-28-2011, 04:54 PM
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Looks like the standard model uses a 21" 13-watt T5, which should average about 700 lumens. I believe the kit also includes a dimmer mechanism though, so you can reduce that.

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post #30 of 43 Old 06-28-2011, 06:59 PM
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Originally Posted by dovercat View Post

According to Joe Kane DVE test disc reference for maximum ambient light test pattern and guide the maximum surround brightness should be 10% of the peak white. CinemaQuest also say "SMPTE recommends the level (brightness) of ambient lighting should be no greater than 10% of the brightest white produced in the video image on the display"

SMPTE RP166 recommends a white level of 120 nits (35fL) with an ambient light level <12 nits (<3.5fL) so max 10%. But I have read in practice they use similar white levels to those use in Europe EBU TECH 3320 version 2 Oct 2010, 70 to at least 100cd/m2 (20.43-29.19+fL) white, the old EBU TECH 3320 version 1.1 May 2008 used 80cd/m2 (23.35fL) as an example of a reference white point. So that would be 17-12% with 15% as the example. EBU TECH 3320 states "If the viewing conditions are standard dim surround (15% as in ITU-R Rec. BT.500-11)" ITU-R BT.500-11 Methodology for the subjective assessment of the quality of television pictures is "Ratio of luminance of background behind picture monitor to peak luminance of picture:~0.15"

So max 10% according to the SMPTE standard, maybe 12-17% using the EBU white level and possibly 15% in practice and according to the ITU.

I'm not sure how things work in the EBU, but I believe the "10% max" that Kane and SMPTE refer to is relative luminance, which would be the equivalent of an ~35% stimulus gray on a 2.2 display. (The maximum ambient reference on the 2003 Component edition of DVE is an ~35% stimulus gray.)

According to DVE, video (in the US) has an average picture (stimulus) level of about 15% over time. In practice I've found a 15% stimulus gray to be a good starting place as a reference for surround light levels with my 34" CRT. Depending on the content, display, etc. you may need to go somewhat higher, or slightly lower than that for better results. I leave enough room in the contrast/white level adjustment on my display to accomodate a range of ambient references between about 13% and 20% stimulus.

If your display has poor (ie brighter) black levels, then you might want to err on the brighter side of this range, perhaps a bit closer to a 20% stimulus range, to help make blacks look a bit deeper on the display.

As always, YMMV.

FYI, on a 2.45 gamma display (which is the reference I use), a 15% stimulus equals about 1% relative luminance, so the ratio of peak white to surround is roughly 100:1 in terms of relative luminance. In this PDF, Poynton proposes a surround level closer to 5% of peak white for video mastering, which would be a 20:1 ratio of peak white to surround luminance. He also suggests surround lighting that's much brighter than standard practice in the US (100 lux vs. approximately 16 to 64 lux in the US for video mastering and sRGB encoding, respectively). IMO, most TV viewers in the US would find a 20:1 ratio of relative luminance very lacking in contrast.

I'm not sure what the 15% figure you're quoting for the EBU above refers to (% stimulus?, absolute luminance?, relative luminance?). If it's relative luminance though, then you're talking about a peak white to surround ratio of only about 7:1, which would be extremely low in contrast compared to video in the US. That would be getting more into the neighborhood of an "average surround" than a "dim surround".

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