Masking Your Edgelit LCD TV for Better Blacks

When it comes to watching movies, a calibrated TV in a darkened room is a magical combination. When I set everything up correctly, and I’ve eliminated any interruptions or distractions, the act of watching a movie becomes a truly immersive experience. Don’t you love the feeling of being in a movie, experiencing it fully, rather than analyzing it? It’s one of my favorite pastimes; in fact, learning how to set up a system that achieves immersion is the primary reason I joined AVS ForumForum nine years ago.

A lot has changed in the past nine years, especially when it comes to TVs and projectors. Today, LED-lit LCDs come in screen sizes that rival small front-projection rigs, and surprisingly excellent image quality is available for under $1000. And LCD technology now dominates TV sales, which was far from the case nine years ago, when plasma was king. Unfortunately, plasma outperforms LCD when viewed in a darkened space, especially when it comes to reproducing deep blacks.

I recently purchased a 60-inch Samsung F5300 plasma as a direct result of the frustration I felt with the dark-room performance of my edgelit 55-inch Vizio M3D550KD. When the lights go out, it exhibits all the trademark flaws of edgelit TVs with pseudo-local dimming—namely, blooming and the dreaded flashlight effect. Those effects were especially distracting when I watched 2.40:1 letterboxed content, as opposed to material presented in a 16:9 aspect ratio.

For the past few years, and continuing to this day, the most popular LCDs are of the edgelit variety, which makes for a very thin TV. However, LED-edgelit TVs suffer in the image-quality department, especially when it comes to how they reproduce shadows and deep blacks. 2014 brings a ray of hope for LED TVs, thanks to the adoption of full-array backlighting by several manufacturers. Backlit arrays boost black level performance by making it possible to shut off LCDs in a very precise manner using local dimming. One of the most prominent examples of the benefits of local dimming is how such a TV can make the black bars in letterboxed content look as dark as what’s achieved by plasma panels.

A few weeks ago, before I picked up my new plasma TV, I repainted my studio with a neutral gray shade. I happened to have a bunch of blue painter’s tape, which is designed for easy removal. I was re-watching Pulp Fiction with my wife Danya, and I couldn’t get over how distracting the edgelit pseudo-local dimming was. Out of frustration, I applied painter’s tape over the letterbox bars. I was amazed at how much this improved the entire viewing experience. The main problem was when the lights came up—blue painter’s tape looks silly on a TV screen. It’s also not practical or economical to tape up a TV every time you want to watch a letterboxed movie. I realized that if I wanted to write about this topic, I’d need to find a way to mask the bars with ease. Whatever I did also had to look okay with the lights on. More importantly, it had to be as easy as possible, and cheap.

I found the solution in the form of a 40 x 60-inch piece of black foam board that I bought at an art-supply store. I put a letterboxed movie up on the screen and took careful measurements of the black bars—on my 55-inch Vizio; each bar measured 3.5 x 48 inches. Using a ruler and a box cutter, I cut two strips to the measured size and attached them to my TV using black gaffer’s tape. The tape acts as a hinge of sorts, making it easy to flip open the masks to expose the entire screen. It was one of the cheapest and easiest mods I’ve ever performed, and the difference it makes in terms of the dark-room viewing experience is dramatic. With many LED-edgelit TVs, it’s the only way to achieve plasma-like (and, in fact, OLED-like) black in the letterbox bars—the foam board is entirely opaque, and in a dark room, it is completely invisible.


Here’s the $10, 40″ x 60″ piece of foam board I used


I taped the ruler to the foamboard using painters tape, so it would stay in place for an accurate cut

When I took the THX Video Calibration Class last February, one of the things I learned is the importance of screen masking for front-projection rigs. A black border improves the perception of contrast, and the same principal works when applied to TVs. With LCD-edgelit TVs, there is an added benefit—masking the black bars hides the machinations of the local-dimming mechanism, which bleed into the letterbox region, resulting in a distracting fluctuation in their brightness.

Some of the latest edgelit LCD designs have the ability turn off the zones in the letterbox region, and I know that backlit arrays with local dimming often offer that option as well. However, there are many edgelit LCDs (and CCFL-lit LCDS as well) that can benefit from masking when watching widescreen (2.40:1 aspect ratio) content. For those TVs, finding a safe, convenient way to mask the letterbox bars can significantly improve the viewing experience in a darkened room. It may be a bit MacGyver-ish, but if it works, why not at least try it?

Here are some photos that show the effectiveness of physically masking the letterbox bars on my edgelit VizioM3D550KD:


For 16:9 content, I flip open the foam board masking to reveal the whole screen


With lights on, the masking offers no real benefit and the foam board is visible. I’m sure it could be improved.


Without masking, in a dark room, the letterbox bars are clearly visible and rather distracting


With masking, the letterbox bars are pitch black in a darkened room


Here’s the same image displayed on my Samsung F5300 plasma. No masking required.