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Bias Lighting and OLED: Why do I need Bias Lighting when my OLED produces "perfect" blacks.

Bias Lighting and OLED: Why do I need Bias Lighting when my OLED produces "perfect" blacks.

Two of the most popular search terms for visitors to this site are:

"OLED eye strain" and "Do OLED's need bias lighting," and this is not surprising. Professional colorists and video editors are quite aware that eye strain can be even worse with OLED than with other display technologies. Why? Because eye strain is caused by the contrast, which causes our pupils to constantly dilate and constrict between dark scenes and bright scenes, and while OLED isn't terribly bright, it does offer incredibly dark blacks.

Besides the capability of the display, we have the content, which doesn't always go to zero. So the content can also look better in spite of the capabilities of the display (SDR 8-bit content - and that's a lot of it, for example). But to fixate on the darkness when HDR offers so much more, I think shortchanges many of the benefits of OLED.

As I mentioned at the start of this post, colorists grading on professional OLED monitors use bias lighting too. It's not about picture quality of the display but rather our ABILITY to see that picture quality. It's how (non-prescription) sunglasses can improve our vision when driving our car. Putting aside the fact that it has ergonomic benefits, it enhances our ability to see the picture. The color appears more vivid and the picture is often sharper. Why sharper? The photopupillary reflex narrows the pupils and just like when we stop down a camera, a greater depth of field falls into focus.

As you know by now, OLED isn't a very bright technology. So, how do bias lights make OLEDs appear brighter? Let's show an example. 

Which white square looks brighter? The one with a simulated dim surround on the left or the one on the right? 


They are both the same brightness level but our brain perceives the square on the left as being brighter. 

Our home theaters are digital, HDR, 4k, but our eyes are much more refined and sensitive analog/human factors in determining what we see. What looks great to us now in home theater technology ALWAYS inevitably sucks in 10 years when the next technology comes along. Remember when we said we couldn't even see the pixels on 1080p? Remember 1080i? We obviously all know that the picture can get better because it always does, as does our ability to pick it apart.

For example, following close behind the other popular searches that bring visitors to our site, "OLED image retention" and "OLED shadow banding" are not far behind. These are limitations of current OLED technology that are also mitigated by proper bias lighting. And even without those limitations, a lot of content was not color graded for OLED displays, and this content benefits from bias lighting as well. 

Joel Silver from ISF likes to say that everyone has opinions about how to set up a TV, but there are defined standards that are accepted internationally. We're all entitled to our preferences too. When I'm working on my computer for non color-critical work, I set my bias lighting much higher than the standards. Because bias lights work on the viewer and not on the TV, it's ok to experiment to find your ideal brightness settings. 

If you suffer from OLED eye stain, we recommended lowering the brightness of your display after installing bias lighting. It sounds counter-intuitive, but a dim surround of bias lighting makes the display look brighter, so you don't need to run the TV at such a high brightness level.

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