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post #751 of 765 Old 02-07-2020, 10:56 PM
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For bias lighting to work properly, does the wall behind the TV need to be white ?
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post #752 of 765 Old 02-08-2020, 01:53 PM
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I purchased the MediaLight Quad from biaslighting.com for my 55" bedroom TV. Turns out that the strips are too long. Is it possible to cut some of the length off without damaging the strips?
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post #753 of 765 Old 02-08-2020, 02:45 PM
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Originally Posted by K_Thompson View Post
I purchased the MediaLight Quad from biaslighting.com for my 55" bedroom TV. Turns out that the strips are too long. Is it possible to cut some of the length off without damaging the strips?
Yes you can. If you look at the installation video on the web site, there are instructions on how to trim the strips to the proper length. It all has to do with exactly where on the strip the cut is made.
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post #754 of 765 Old 02-08-2020, 06:20 PM
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For bias lighting to work properly, does the wall behind the TV need to be white ?
Neutral gray to white is recommended. This post explains why:


https://www.avsforum.com/forum/139-d...l#post56820182



The darker the shade of gray is, the more brightness will be required from the bias light to achieve the correct illumination on the wall. A lighter shade will help enhance the perceived black level from the display when viewing with higher room light levels. These quotes explain how this works:


"Contrast could be considered to be the most significant quality that impacts not only the perceived depth of an image, but also affects the apparent sharpness.....While the luminance level of a given image affects how the eye perceives contrast and detail, the ambient conditions surrounding the image can also have a dramatic impact. This phenomena was studied by Bartleson and Breneman (1967) to examine the impact of perceived contrast based not only on the luminance level of the image but taking into account the surrounding ambient luminance levels as well. Their results showed that the perceived contrast increased as ambient luminance increased. With the increase in ambient luminance, the eye interprets black levels as being darker while the impact to the white level is minimal. Since the perceived difference in dark areas is greater under the higher ambient luminance conditions, the perceived contrast is higher. It is a natural tendency to want low ambient luminance levels to strive for "better" perceived image quality and what is thought to result in higher contrast. However, in reality, the opposite is true. This tendency may be justified for current direct view CRT televisions due to the issue of glare that results from the glossy surface of the glass tube [also true for certain flat panel displays today]. With less ambient luminance, the glare is reduced- but it may be important to keep some ambient luminance behind the television [as in the case of bias lighting] to keep the perceived contrast higher.....While sharpness can affect the apparent contrast of an image, the converse is true in that contrast can also impact the apparent sharpness of an image. Images that have lower contrast will appear to be not as sharp as an image of the same content, but with higher contrast.....A subjective study was then conducted to verify the impact that ambient lighting has on perceived contrast. Several non-technical (and thus presumably non-biased) and technical observers were asked to compare a series of images with various ALL [average luminance levels] under different ambient luminance extremes in order to understand the impact that ambient viewing conditions might have on the perceived contrast between the two television technologies [CRT and DMD (DLP RPTV)]. Under dark ambient conditions, the result for images with an ALL > 5% was found to be equal between the CRT and the first DMD display. However, under bright ambient conditions (about 250 nits of luminance on the wall behind all of the units), the DMD display was favored over the CRT by 50% of the observers as having higher perceived contrast.....This proved that ambient conditions have the effect of potentially raising the black level threshold of the eye above the actual black level of the television such that the perceived contrast ratio is higher." from the SMPTE Journal, 11/02. 'The Importance of Contrast and its Effect on Image Quality' by Segler, Pettitt and Kessel

"Their experimental results, obtained through matching and scaling experiments, showed that the perceived contrast of images increased when the image surround was changed from dark to dim to light. This effect occurs because the dark surround of an image causes dark areas to appear lighter while having little effect on light areas (white areas still appear white despite changes in surround). Thus since there is more of a perceived change in the dark areas of an image than in the light areas, there is a resultant change in perceived contrast.....Often, when working at a computer workstation, users turn off the room lights in order to make the CRT display appear of higher contrast. This produces a darker surround that should perceptually lower the contrast of the display. The predictions of Bartleson and Breneman are counter to everyday experience in this situation. The reason for this is that the room lights are usually introducing a significant amount of reflection off the face of the monitor and thus reducing the physical contrast of the displayed images. If the surround of the display can be illuminated without introducing reflection off the face of the display (e.g., by placing a light source behind the monitor that illuminates the surrounding area), the perceived contrast of the display will actually be higher than when it is viewed in a completely darkened room." from 'Color Appearance Models,' by Mark D. Fairchild, Ph.D., of the Chester F. Carlson Center for Imaging Science: Munsell Color Science Laboratory


These quotes are from the "sticky" thread in the Display Calibration section of the forum, titled 'D65 Video Bias Lighting- Fundamental Theory And Practice'


Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.
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post #755 of 765 Old 02-08-2020, 10:01 PM
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Thanks. My wall is black. No bias lighting for me.
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post #756 of 765 Old 02-08-2020, 10:15 PM
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Quote:
Originally Posted by Jim McC View Post
For bias lighting to work properly, does the wall behind the TV need to be white ?

It should be a neutral color.


Oops. I see GeorgeAB beat me to it

I never trust an atom, they make up everything.
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post #757 of 765 Old 02-09-2020, 12:37 AM
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Black is neutral !
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post #758 of 765 Old 02-09-2020, 11:43 AM
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Quote:
Originally Posted by AustinJerry View Post
Yes you can. If you look at the installation video on the web site, there are instructions on how to trim the strips to the proper length. It all has to do with exactly where on the strip the cut is made.

Thanks for pointing me to that page. Unfortunately the picture on the installation page showing where to cut looks nothing like my strips so I'm still not sure where it's safe to cut. I sent them a message for clarification.


The first pic is from their website. The second pic is my strip. They're very different.
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post #759 of 765 Old 02-09-2020, 11:50 AM
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Just got a response to my question from Jason at Biaslighting.com (that was fast!!) So for those interested, here's where to cut on the MediaLight Quad strips:
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post #760 of 765 Old 02-09-2020, 12:21 PM
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Quote:
Originally Posted by K_Thompson View Post
Just got a response to my question from Jason at Biaslighting.com (that was fast!!) So for those interested, here's where to cut on the MediaLight Quad strips:
My strip looks like yours, and that is exactly where I suspected the cut should be made. When I reached out to Jason with a different question, he responded very quickly as well. Nothing is more valuable than a vendor who provides good support for a product. Respect!
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post #761 of 765 Old 02-10-2020, 10:00 PM
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Your wall is gray. It’s all relative. If your wall was painting with Vantablack you’d have issues, but not with commercial black paint.

Trust me, black paint reflects light, you just need to run the lights brighter to get reference levels off the wall. I use a black fabric scrim behind my laptop in the lab next to my integrating sphere even though the wall behind it is painted with Munsil N8. I use N8 because my kids also use the room for ping pong, and I didn’t want it too dark. . I use the scrim to lessen the reflections to the rest of the room because N8 is pretty light.

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Thanks. My wall is black. No bias lighting for me.
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Jason Rosenfeld
Scenic Labs, LLC
Publisher of Spears & Munsil Benchmark UHD HDR Benchmark.
Maker of The ISF-certified MediaLight 6500K Bias Lighting System

Last edited by Scenic Labs; 02-10-2020 at 10:17 PM.
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post #762 of 765 Old 02-10-2020, 10:16 PM
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Yes, I need to update that tomorrow morning as we fully transitioned to that strip PCB, but we’re also launching new Medialight v2 and MediaLight LX1 series (budget series at roughly half the price but with the same CRI of 98 and SPD that is coming to the new MediaLights) lights soon and they look a bit different.

I can post photos if you want to see what those strips look like as well as outline the changes coming to the entire medialight range, if you want.

The first pic is from their website. The second pic is my strip. They're very different.[/QUOTE]
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Jason Rosenfeld
Scenic Labs, LLC
Publisher of Spears & Munsil Benchmark UHD HDR Benchmark.
Maker of The ISF-certified MediaLight 6500K Bias Lighting System
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post #763 of 765 Old 02-13-2020, 02:08 PM
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................... even though the wall behind it is painted with Munsil N8. I use N8 because my kids also use the room for ping pong, and I didn’t want it too dark. . I use the scrim to lessen the reflections to the rest of the room because N8 is pretty light.

What is preferred? N5?
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post #764 of 765 Old 02-13-2020, 03:54 PM
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What is preferred? N5?
Professional post-production color correction and VFX suites usually recommend a matte N5 all around. That's in the middle of the Munsell range of neutral grays and comparable to an 18% reflectance photo gray card. That makes for a fairly dark room but helps minimize screen reflections and aids rapid color adaptation, which can take a recommended half-hour, more or less on average. There are other light sources in the room from additional computer monitors, task lights, LED indicator lights on electronics, etc.







https://www.facebook.com/theColourSp...7463904867437/

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post #765 of 765 Old 02-14-2020, 01:58 PM
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Professional post-production color correction....

Thank you George.
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