Originally Posted by OLED4UNME
Numbers have very little to do with how the human visual system perceives contrast... Our eyes do not work like mechanical meters.
When you have an area of black right near a bright area of white, the human visual system can only perceive a very limited amount of contrast. The only thing that matters is the contrast which your eyes are able to perceive... if there is something black right next to something bright, we cannot detect a large discrepancy in contrast...
At any given time, the eye's static
contrast ratio or dynamic range is somewhere between 1,000-15,000:1 (10-14 stops). In situations of extreme low-light viewing (where our eyes have adjusted to use rod cells for "scotopic/night vision") our visual system can accommodate an even larger brightness range.
When viewing a "real-world scene", our eyes can focus on different parts of the scene and dynamically adapt and adjust for the different light levels of those different areas - our pupils open and close for the different brightness regions of the scene, giving them the ability to make out tons of detail in both the dark parts and bright parts of the scene. Since it can dynamically
adapt to different brightness levels by closing and opening the pupil, the human eye can perceive scenes with a very high dynamic contrast ratio, anywhere from 1,000,000-17,000,000:1 (or 20-24 stops of light).
Additionally, the human brain has an amazing ability to take-in all those details, intelligently interpreting the information from our eyes, and "create" a single mental picture that takes into account all those details.
Now our perception
of detail and sharpness is based intrinsically on contrast
. It is edge contrast
especially which allows our brain to separate and recognize one object from another.
Another advantage to HDR displays, and especially OLEDs, is that, since viewers experience contrast as the difference between the brightest and darkest pixels within an image, and since edge
contrast is a visual cue for sharpness, having dramatically brighter pixels, even a few of them in the top highlights, means that the perceived contrast of the image will be dramatically higher, and details will appear to be much crisper... HDR highlights on an OLED TV add contrast that make the edges
by which we evaluate sharpness really "pop".
Furthermore, because of their much deeper blacks levels, a 500 nits specular highlight will indeed seem much brighter on an OLED TV than the same 500 nits specular highlight on an LCD display who's black levels are nowhere near as deep.
This is due to the "Perceptual Contrast Effect
". The way we judge pretty much anything is in comparison with something else. Put a bright object next to a dark object and it will seem brighter.
(This is the same reason that "blacks" on a TV screen appear darker when you use "bias lights".)
For example, in the image below, the grey square on the left (A) "seems" brighter/lighter than the one on the right (B), which appears darker/dimmer. In reality, they are both the same shade of grey. That is the "Perceptual Contrast Effect
It's also important to mention that room lighting
will also have a significant impact on the "perceived" contrast of the display.
Additionally, it cannot be over-emphasized that HDR grading is not always about making everything brighter
. Just making everything brighter is like doing a music mix where you simply make everything louder. You're not really taking advantage of the ability to emphasize specific musical details via increased dynamic range, you're just making individual details harder to hear amongst all the increased energy bombarding the audience.
From professional colorist Alexis Van Hurkman
: "On one job I was grading, one of the characters of a scene had brass buttons on their jacket, which were natural candidates for putting out some HDR-strength glints. I keyed and boosted them, but I was moving so fast that the first adjustment I made had the buttons glowing like little suns. I paused to take in the effect, and the client and I simultaneously burst out laughing, the result was so completely ridiculous. It goes without saying that HDR-strength highlights should be motivated, but I was surprised by just how instantly hilarious the wrong use of these highlights was."
"I also see the ability to have these sorts of squint-inducing highlights as another creative opportunity, one that's been available to audiences looking up at the stage lighting of plays, musicals, and concerts for years. If you're careful not to abuse the privilege, I think the ability to cut to a bright frame, surprise with a sudden flare or shower of sparks, or grade a light-show with similar physiological impact to the real thing can create compelling narrative opportunities in our storytelling."