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Light Behind TV


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21 replies to this topic

#1 of 22 OFFLINE   JacobK

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Posted February 02 2004 - 12:30 PM

I just bought a TV and was calibrating it with DVE. I noticed they said that behind a CRT there should be a light. I was wondering if there is a certain kind of bulb/light that I should get or would any light work. Also will this make a difference?
Thanks for the advice.
Jacob

#2 of 22 OFFLINE   Mike-C

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Posted February 03 2004 - 02:40 AM

Jacob,

Any bias light you place behind your TV should rate at 6500k, so any old bulb wont cut it.

Cinemaquest sells sells specialty lights/fixtures that are designed as TV bias lights. There are also a lot of people who have had success with aquarium lights bought at petstores.

If you search the forum under "Tweaking, connections and Accessories" you may be able to find a few more posts about this subject.

cinemaquestinc.com/ideal_lume.htm

#3 of 22 OFFLINE   Cameron Yee

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Posted February 03 2004 - 09:57 AM

I bought an inexpensive 16" fluorescent fixture from the hardware store and found a local lighting store that sells a 6500K tube. Be sure the ballast on the fixture doesn't buzz and consider the possibility it may introduce AC noise.

I was using the bias light for awhile, but find that ultimately I'm not that particular and am fine with having a small lamp on somewhere in the room. I know this theoretically throws off color perception, but I'm not picky enough to notice. My main intent is to prevent eye strain. In the theater this is not an issue because (ideally) the expanse of the screen should fill up the majority of your field of view. In most homes the television occupies a relatively smaller portion of your field of vision. Such a bright source surrounded by darkness causes strain.
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#4 of 22 OFFLINE   Guy Kuo

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Posted February 03 2004 - 10:14 AM

I went so far in my RPTV days as rigging up a relay so my bias lamp behind the set automatically turned on whenever the TV came on. You have to pull the set forward a few inches to fit the lamp. BTW 6500K can mean a lot of different colored lights. The Cinemaquest unit has a special bulb which is very very close to D65 the exact shade of white for video. You won't get anything nearly that accurate in a home depot or pet shop. Most 6500K bulbs are going to be too green, too magenta or some other off target color.
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#5 of 22 OFFLINE   Andy Goldstein

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Posted February 03 2004 - 10:25 AM

i just used a dual halogen lamp unit designed for under-cabinet use. stuck it on the sloped rear face of the rptv. it has two 10-watt bulbs in it, and a 2-position switch. (3 if you count off). instant cure for eye strain and tv induced headaches.

ag.
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#6 of 22 OFFLINE   Dean T

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Posted February 04 2004 - 07:13 AM

Actually Guy 6500K refers to a very specific frequency of light. We have this debate on light all the time in one of my other hobbies, reeftank keeping.

While some bulbs do lean toward either end of the spectrum depending on what materials they are made with, for the most part purchasing a 6500 Kelvin bulb from a pet supply store (petsmart and pet supermarket don't count, you won't find the right type of bulbs there) should get you the natural white light needed. Check at a pet supply store that carries saltwater corals and fish. They could help you out in finding the right bulb.

There are also other frequency bulbs such as the 10K and 14K halides that would give you an even better white. They can be pricey though.

Just some more info to chew on!!

#7 of 22 OFFLINE   Scott L

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Posted February 04 2004 - 07:28 AM

You need a 6500k flourescent with a high CRI. I went with a fixture from Home Depot and the Philips Daylight F20T12/D. I bought this back in 2k1 and keep it on almost 24/7. It's never burned out on me.

Posted ImagePosted Image

Helps greatly with eye strain.

http://www.keohi.com....klighting.html

#8 of 22 OFFLINE   Doug_L

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Posted February 04 2004 - 07:30 AM

Dean T: I assume you mean 6500 degrees Kelvin, not Kalvin, right?

I've been a believer in the bias light for over 4 years now, but I took the cheap route. A simple 20 watt light fixture behind the TV does it for me: it's not perfect, but it's a whole lot better than nothing.

#9 of 22 OFFLINE   Guy Kuo

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Posted February 04 2004 - 08:03 AM

Not quite. The 6500K on the bulb specificatin refers to a correlated color temperature. It does not completely tie down the relative amounts of RGB, only that the color is closest the 6500K black body point. Some variation in coloration will be seen across bulbs which are labeled as 6500K. On the other hand, the D65 color standard is a much more rigorous specification of CIE color because it is a specific RGB point. You can be off the curve and still have a correleated color temp of 6500K.

see

http://www.schorsch....ossary/cct.html

http://lightingdesig....color_temp.htm

http://www.colorfact....aturemeter.htm

http://www.gamma-sci...temperature.htm




quote from the smartavtweaks site http://www.smartavtw...m/absolute.html explains it nicely ----


The Color Temperature chart shows again the same information, but in this case, as a “Correlated Color Temperature” calculated from the above xy coordinates. Note that is Color temperature diagram is probably the least informative of the three, as the Correlated Color Temperature is particularly insensitive to green in the regions of color space where we will be operating. So you may find that during the calibration process, the Color Temperature may read very close to the desired 6500, but that the SMART Color indicates that green is either too high or to low. This is because 6500K does not describe a precise location in color space, (unlike D65) but in fact, a whole locus of lines that can have significant variation in the green magenta balance. -----


In other words 6500K is a specific color IF and only IF you also specify you are on the black body curve. A fluorescent bulb is specified as a correlated color temperature, not necessarily and usually not on the black body curve.
Guy Kuo
Director - Imaging Science Foundation Research Lab

#10 of 22 OFFLINE   Dave Miller

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Posted February 06 2004 - 12:41 AM

Jacob,

I did the same thing that Scott L did in the pics above. Bought a fixture from Home Depot, same bulb, etc. The only difference is I mounted the fixture to the back of my television with heavy duty velcro and the fixture faces the other direction. If you are looking at the side profile of my Tosh 65h80, I placed the fixture just at the bottom of the angled section (where the mirror is housed on the inside). This way the light is directed up the back wall. Works well.

Right after I got my TV and before I did this, I was very frustrated b/c when I would watch my TV at night I got head aches. I read up on eye strain, installed the light and solved the problem.

I also hooked the power plug up to a switched outlet on my receiver so the light comes on whenever I power up my receiver.

Peace,

DM
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#11 of 22 OFFLINE   Cameron Yee

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Posted February 06 2004 - 03:11 AM

I also have a Toshiba RPTV but I was leary of sticking anything to the surfaces, so I used pegboard hooks and hung the fixture from the lower portion of the set that has pegboard material. The fixture I use is not as large as the one submitted by the other poster. It is only about 2 inches wide and 18 inches long, so no concerns about it blocking the vents. The position is perfect for me to just reach around and turn on, though I have considered connecting it to my receiver's AC outlets.
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#12 of 22 OFFLINE   Dick White

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Posted February 06 2004 - 03:36 AM

I have been using a flourescent desk lamp that sits on top of the set. I'm able to adjust the arm so that it is behind the set and shining on the wall. It stays on 24/7. The only problem is that I had to replace the bulb once and could not find a replacement with the same color temp as the one that came with it. It probably wasn't 6500 K, but it was much cooler than what I have now. Guess I need to visit some pet supply stores.

#13 of 22 OFFLINE   Guy Kuo

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Posted February 06 2004 - 03:58 AM

"Pet Store" ---- Well I tried.

At any rate, you may find this auto switching outlet useful http://www.sears.com....id=00924031000

Plug TV into the master outlet and the slave should turn on your lamp when the TV comes on. It may take trying more than one unit. They don't all have the same senstivity to detect power drain on the master.
Guy Kuo
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#14 of 22 OFFLINE   Gregg Loewen

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Posted February 06 2004 - 05:43 AM

hehe,

Thanks Guy!

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#15 of 22 OFFLINE   GeorgeAB

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Posted February 07 2004 - 10:17 AM

Guy Kuo's comments deal with issues that are not discussed as frequently as the eye strain benefits of backlighting. Color perception is not so well understood outside of the professional community. The Society of Motion Picture and Television Engineers (SMPTE), the International Organization for Standardization (ISO) and others recommend very specific types of ambient lighting be used in professional electronic display environments. SMPTE's recommendation for critical video viewing environments is as near as possible to CIE D65. That is also the specification for video monitor calibration.

There are additional specifications and recommendations pertaining to other characteristics of a monitor's environment that enhance both the quality and consistency of video imaging and production. Cinematographers, telecine colorists, computer graphics artists, digital photographers, etc., work very hard to achieve a certain look in their work. The viewing environment conditions in the production areas for these crafts are designed according to proven methods. These methods transfer well to home theater.

The average "Joe" who just wants to watch TV cares little for such issues. Most cinema/videophiles invest much more time and money toward obtaining the best picture quality in their home theater. No video display can look its best if the viewing environment is not optimized. Poor room conditions can compromise and contaminate a video display just like they can the sound system. Videophiles who have spent the money to have their TV professionally calibrated would do well to seek a better understanding of these issues.

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

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#16 of 22 OFFLINE   Dave Schofield

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Posted February 08 2004 - 04:42 AM

I don't know much about color temperatures, etc, but I have one simple question that I think needs to be addressed. Even if you were to find the "perfect" 6500 k bulb, wouldn't the paint color of the relfective wall have more impact on the actual color you see?

#17 of 22 OFFLINE   Guy Kuo

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Posted February 08 2004 - 05:41 AM

The paint does alter the color - tremendously. That's why a neutral paint color is recommended behind the screen.

One advantage of having a bulb which is actually D65 rather than merely a correlated color temp 6500K is that a D65 bulb can be used to judge whether or not your gray scale needs profesional calibration. If the color of white on your screen differs from the color of light from the bulb, your grayscale is off and you should consider having it professionally calibrated. This is a great way to see how laughably inaccurate the "warm" or "movie" mode comes from the manufacturer. Without an accurate color reference (D65) bulb, you don't have a basis for comparison.
Guy Kuo
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#18 of 22 OFFLINE   GeorgeAB

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Posted February 08 2004 - 08:29 AM

Here's a link to compare the spectral content of various light sources. http://www.videoesse...ts.htm#spectral . It is easy to see from these graphical images how screwy the coloration of typical incandescent illumination is when compared to video white. Even nearly-white walls can look significantly better when using a 6500K backlight, compared to incandescents or other types of fluorescents. The spectral precision of the 6500K fluorescent bulb is not so critical if the wall is not truly neutral.

Many owners of better quality TVs live in rental property with mandated white walls. White is neutral! The off-whites that many people use are still an improvement over vivid colors behind a TV. The Kodak 18% gray card is often used to compare to a paint or fabric that may be placed behind a television. It's actually darker than most people would want on a wall but it is an easily-found true reference for neutral. Most camera shops have them for about $15.00 retail.

For about three times that, we have Munsell Neutral Value Scale fan decks (matte version) available on our site for a much broader range of shades of gray. The Munsell Color Order System is used by SMPTE to quantify what neutral and nearly-neutral is. Instead of just one shade of dark gray, the fan deck gives you 31 steps of color chips, from black to white, to use for comparisons.

It's hard to fully communicate in just words how wonderful a properly calibrated TV looks in a truly neutral viewing environment. Not that many consumers provide a reference wall behind their display so not many have experienced the benefits. A neutral background lit with D65 illumination is the best possible frame to place around the art you display on the canvas that is your TV screen.

Some people have the mistaken idea that the entire room has to be gray. Just the area behind the TV, within your field of view when observing the screen, needs to be neutral to preserve correct color perception. The SMPTE spec for the rest of the room allows for Munsell nearly-neutrals. These are fairly subdued pastels that cover the entire range of hues and can vary somewhat widely in value (light to dark) and chroma (richness of color). There is no excuse for not being able to achieve a varied, pleasing and interesting room decor for a reference video viewing environment. All it takes is the understanding and the tools.

Best regards,
G. Alan Brown
www.cinemaquestinc.com

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#19 of 22 OFFLINE   Ryan_McCormick

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Posted July 30 2005 - 10:40 AM

The wall color behind the TV is actually an earth tone brown. Will that affect the lighting?

#20 of 22 OFFLINE   GeorgeAB

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Posted August 01 2005 - 04:58 AM

Any color except neutral gray or white will tint the light reflecting off of it. True neutral is composed of equal amounts of the primary colors, when discussing illuminants. When referring to pigments, true neutral will be that which reflects light without altering its spectral content (color composition).

There is no such thing as CIE D65 gray paint, only gray paint that will not alter D65 illumination when reflecting it. Brown may be loosely referred to as a "neutral" color in certain design fields. Technically, it is not neutral.

We recognize the color of a pigment from the light it reflects. A rich red pigment theoretically absorbs all light except that which we recognize as red. The light reflected off of such a wall would be red. That's why those rich red theaters you've seen in the magazines may be great for simulating a "palace" performance theatre with all the room lights are on, but lousy for front projected movies. Each time a predominantly bright scene is projected on the screen, the screen reflects light into the room. The illuminated red room filters out that light and only reflects red illumination back onto the screen. This tints the picture on the screen and adds red over the top of the image. This would be similar to placing a pale red filter over the projector's lens.

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

"Advancing the art and science of electronic imaging"