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Posted by robotnikman 6 days ago

LG's new 1Hz display is the secret behind a new laptop's battery life(www.pcworld.com)
214 points | 101 commentspage 2
jerryslm 2 days ago|
Today I learned, laptop comes with backlit vs edgelit panel. And, they have different energy consumption.

There are also mini LED laptop for creative work. Few more things to check before buying new laptop.

hedora 2 days ago|
I wouldn't get a mini LED laptop for creative work. We have a mini LED TV, and manufacturers need to choose one of these two problems because of physical limitations:

- The LEDs for a mostly dark region with a point source are too bright so the point source is the correct brightness. Benchmark sites call this "blooming" and ding displays for it, so new ones pick the other problem:

- The LEDs for mostly dark regions with a point source are too dim so the black pixels don't appear gray. This means that white on black text (like linux terminals) render strangely, with the left part of the line much brighter than the right (since it is next to the "$ ls" and "$" of the surrounding lines). Also, it means that white mouse pointers on black backgrounds render as dark gray.

For creative work, I'd pick pretty much any other monitor technology (with high color gamut, of course) over mini LED. However mini-LED is great if you have a TV that is in direct sunlight, since it can blast watts at the brightest parts of the screen without overheating.

dizzy9 2 days ago||
Perhaps it can do 50Hz, which may be beneficial for emulating PAL systems.
whalesalad 2 days ago||
Ostensibly any display capable of VRR should be able to operate at any range.
hedora 2 days ago||
You don't need VRR for this, but there are some step functions of usefulness:

24Hz - now you can correctly play movies.

30Hz - NTSC (deinterlaced) including TV shows + video game emulators.

50Hz - (24 * 2 = 50 in Hollywood. Go look it up!) Now you can correctly play PAL and movies.

120Hz - Can play frame-accurate movies and NTSC (interlaced or not). Screw Europe because the judder is basically unnoticeable at 120Hz.

144Hz - Can play movies + pwn n00bs or something.

150Hz - Unobtanium but would play NTSC (deinterlaced), PAL and movies with frame level accuracy.

240Hz - Not sure why this is a thing, TBH. (300 would make sense...)

martijnvds 1 day ago||
240 = 2 x 120, or 4 x 60 (or 8 x 30)
Dwedit 2 days ago||
You can use CRU (custom resolution utility) to add 50Hz to most screens.
amelius 2 days ago||
So if a pixel is not refreshed, it doesn't use any power?
layer8 2 days ago||
For sample-and-hold panel technologies like LCD and OLED, refresh is about updating the pixel state (color). There is a process that takes place for that even when the pixel data remains unchanged between frames. However, the pixels still need to emit light between refreshes, which for LCD is a backlight but for OLED are the pixel themselves. The light emission is often regulated using PWM at a higher frequency than the refresh rate. PWM frequency affects power consumption as well. Higher PWM frequency is better for the eyes, but also consumes more power.
hedora 2 days ago||
OLED is fundamentally not sample and hold, because it is using PWM, right?

Ignoring switching costs, keeping a sample-and-hold LED at 0%, 50% and 100% brightness all cost zero energy. For an OLED, the costs are closer to linear in the duty cycle (again, ignoring switching costs, but those are happening much faster than the framerate for OLED, right?)

(Also, according to another comment, the panel manufacturer says this is TFT, not OLED, which makes a lot more sense.)

DoctorOetker 2 days ago|||
I don't believe LED-pixel displays use PWM. I would expect them to use bit planes: for each pixel transform the gamma-compressed intensity to the linear photon-proportional domain. Represent the linear intensity as a binary number. Start with the most significant bit, and all pixels with that bit get a current pulse, then for the next bitplane all the pixels having the 2nd bit set are turned on with half that current for the same duration, each progressive bitplane sending half as much current per pixel. After the least significant bitplane has been lit each pixel location has emitted a total number of photons proportional to what was requested in the linear domain.
amelius 1 day ago||
So for an 8bit color display you have 24 lines of various currents going across each row (or column) of pixels?
DoctorOetker 1 day ago||
There are more efficient ways of achieving this, but you certainly don't need a separate conductor for each bitplane, but obviously you need separate strings for each color channel.

So to ignore the colorwise overhead lets pretend we just have a single color channel.

You could even arrange all LED's in series and short out (bypass with mosfet) those LED's that should NOT be lit.

Then you can just energize an inductor until the appropriate current is reached and then flash a certain amount of charge through the LED string.

One can choose between reusing the same inductor for the different currents or having separate inductors each for their own current levels.

It would require bypass transistors for each LED, but there are support electronics for each LCD pixel too, as a comparison.

The 24-bit color display (3x8) would actually result in many more bit planes after gamma deflating to the linear photon proportional domain.

layer8 2 days ago|||
PWM still counts as sample-and-hold, because it sustains the brightness throughout the duration of a frame, resulting in significant motion blur. The converse are impulse-driven displays like CRT and plasma.

LED backlights using PWM likewise don’t change the sample-and-hold nature of LCD panels.

My understanding is that PWM switching costs aren’t negligible, and that this contributes to why PWM frequencies are often fairly low.

etchalon 2 days ago|||
If the screen is only refreshing once per second, less energy is used to refresh the screen. The pixel uses the same amount of power.
amelius 2 days ago||
I was not under the impression that sending some control signals took that much power.
etchalon 2 days ago|||
Maybe not, but doing it once a second instead of 60 times a second is a pretty massive savings.
tokai 2 days ago|||
You have to compute the new frame too. I would assume that is were most of the power use is.
tosti 2 days ago|||
E-ink displays can do this. That's why they're used in ereaders. Display in TFA OTOH emits light, so definately not.
perching_aix 2 days ago||
It does, especially with LCDs like this, where the backlight is the primary driver of the power consumption of the panel.

I'm not even sure how they got their 48% figure. Sounds like a whole-system measurement, maybe that's the trick.

ricardobeat 2 days ago||
Apple introduced variable refresh rate back in 2015. That’s over a decade ago, I’m sure there’s some new tech involved here, but quite the omission.
hu3 2 days ago||
Apple might have convinced some gullible customers that this was something new.

But to the rest of the world variable refresh rate existed for years by then. As is with most Apple "inventions".

In this case the patent goes back to 1982: https://patents.google.com/patent/US4511892A/en

dlcarrier 2 days ago|||
And if Apple introduced it a decade ago, then it's at least five years older than that.

What's new here is the 1 Hz minimum.

thelastgallon 2 days ago|||
Apple doesn't manufacture panels, they buy from others. I wonder how Apple can claim they have this feature.
embedding-shape 2 days ago||
Stroke CRT displays been able to do variable refresh rate since like the 80s, quite the omission there buddy.
bfivyvysj 2 days ago||
Make a new phone with this please.
hasperdi 6 days ago||
this is just regurgitating the manufacturer's claim. I believe it when I see it. Most of display energy use is to turn on the OLED/backlight. They're claiming, because our display flickers less, it's 48% more efficient now.
hasperdi 1 day ago|
[dead]
sciencesama 2 days ago||
imagine what it will do to neo !
stack_framer 2 days ago|
I once had an external monitor with a maximum refresh rate of 30 Hz, and mouse movements were noticeably sluggish. It was part of a multi-monitor setup, so it was very obvious as I moved the mouse between monitors.

I'm not sure if this LG display will have the same issue, but I won't be an early adopter.

dghlsakjg 2 days ago|
Read the article.

The display has a refresh rate of 120hz when needed. The low refresh rate is for battery savings when there is a static image.

Variable refresh rate for power savings is a feature that other manufacturers already have (apple for one). So you might already be an early adopter.