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Comment by Veedrac | Hacker News Reader

I certainly appreciate high DPI screens, and clearly a lot of people agree with me. There's certainly not "no reason" - it's the primary point of interface from the computer to the human, so of course there's value in optimizing it.

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Sure, "optimize" it. But if you put a 300 ppi and 200 ppi screen next to each other and asked users "Do you want the higher resolution screen or do you want an extra 2 hours of battery life?" I don't think they'll choose the screen. I have 4K in a 24" desktop screen, and that pixel density is plenty high.

In the tradition of digital camera manufacturers and countless other tech companies, HP chasing the consumers who know that "4K" is the next-big-thing and that bigger numbers are always better.

To be fair to HP, they're doing it because it works. Doesn't mean it's "optimized." Or that I'd take one over the 2016 MBP.

Lots of manufacturers have done that. The high resolution screens are frequently an optional item with known costs to battery life, and which directly cost money. If as you suggest they wouldn't sell, I seriously doubt we'd be seeing them so pervasively.

Also, pixels densities don't scale linearly. Having a 200 DPI desktop screen isn't equivalent to a 200 DPI laptop screen, else phones would still be at 480 x 270 or whatever.

Oh I'm not suggesting they don't sell, just that they shouldn't.

It's like how people will buy an 18MP camera with worse optics instead of a great 12MP camera because it has a bigger number. And god forbid they ever need to make a 20x30 print, you wouldn't want to see any pixels in that.

To take the opposite extreme of your 480 x 270 cell phone example: You can get an Xperia Z5 with a 5.5" 4K screen, but that doesn't mean it makes any sense.

4k phones aren't taking over the same way 4k laptops are. The best selling flagships don't have 4k screens. The largest push for 4k phones seems to be with VR as a justification, and VR sorely needs pixels.

Your comparison with phones would be more convincing if they ever really took off, but as far as I'm aware it never happened.

Can a phone drive that many pixels at a speed that's useful for VR?

4k makes an appreciable improvement on 15" screens, on 13" screens it's much more questionable, but OSX handles HiDPI well enough that I appreciate it

The problem is that the choices aren't well balanced. You can either have 1080p, which is noticeably low-resolution, or you can take a 30-40% battery life hit for 4k. Almost nobody except goes after the sensible middle ground of a 200 dpi display.

I expect the primary advantage of 4k for most people will be the ability to scale 2x and retain a decent resolution. You don't save much (cost, battery life) by going to an intermediary size, but lose flexibility. On top of that, there are definitely noticeable improvements to be had significantly above 200 dpi.

I wonder how many people opt for the higher density assuming it'll make a significant difference without really knowing what the visual threshold for being able to see a noticeable difference is.

^ This right here is my complaint, thanks for putting it succinctly.

HiDPI on Linux is still bad/spotty. If you run Linux, you'll see the difference quickly.

Typed on a Razer 13" with QHD display that I'm still constantly messing with (FC25 Cinnamon).

Would that be because you're using a desktop that's not HiDPI ready?

I had massive issues with the others (KDE5/Plasma, Unity, Gnome 3, etc). Cinnamon is actually the best in terms of usability. The other windoow managers were straight busted in terms of UI scaling, ability to sleep, disable the touchpad while typing, screensaver, etc.

Have you actually compared the same content on a 200 PPI screen vs. a 300 PPI screen? Even though you cannot see the individual pixels, text on a 300 PPI screen appears much sharper (when scaled to be the same physical size, of course).

The "visual threshold" doesn't mean "you will not see anything smaller than this so it cannot physically matter". You can still see a hairline even if it's less than 1/300 inch wide.

PPI (DPI) is actually bad unit for display's "sharpness", because it makes difficult to comparise different types of devices, meant to be watched from different distances. The correct universal unit is pixels-per-arcsecond, i.e. the ratio between PPI and viewing distance, making possible to compare e.g. mobile screen with video projector image.

"6/6 vision is defined as the ability to resolve two points of light separated by a visual angle of one minute of arc, or about 320–286 pixels per inch for a display on a device held 25 to 30 cm from the eye."

Around 200 PPI seems ideal, with good margin, for typical laptop screen viewing distance (50…60 cm). Empirical test with my 15" Retina Macbook confirms this: I have to put my face impractical close to screen before sharp edges (e.g. in letters) start to look soft.

https://en.wikipedia.org/wiki/Visual_acuity

A 1080P screen on a 15" laptop is high enough resolution that the smallest readable text is getting hard to read. Doubling that resolution in either direction may not be pointless, but if it also destroys my battery life then it's certainly not improving the device as a whole.

Edit: As pointed out below, that's a terrible way to describe it. :P I meant that text at the smallest legible pixel size is physically small enough that it'd be hard to read even at a larger resolution.

The smallest readable text is always hard to read, as otherwise you'd go smaller. I'm not sure what that measure proves. Going from 1080p to 2160p makes that same size text much easier to read, because it's much sharper.

There's a lower limit determined by pixel size, and a lower limit determined by the angular size of the letters as seen by the user. For me, at least, the two are about the same on a 1080p 15" screen. A little more resolution (1440p maybe) could be useful but even that's past the point of diminishing returns.

You’re comparing a 150 ppi (2 megapixel) 1080p display to a 300 ppi (8 megapixel) 2160p display. Many of us agree that displays in the 100–150 ppi range are noticeably pixelated at typical laptop viewing distance.

But you should be comparing to a ~200–230 ppi (4–5 megapixel) display, which at laptop viewing distances (let’s say 24 inches) is just about at the limits of human perception. Dense enough to not be worth the hit to performance/cost/battery to bother going much denser. The Apple 15 inch “retina” display is 220 ppi, 2880 x 1800 pixels. (That’s the analog of 1620p but at a 16:10 rather than 16:9 aspect ratio.) The Apple 13 inch display is 227 ppi, 2560 x 1600 pixels, the 16:10 analog of 1440p.

[Note: corrected Apple laptop pixel count.]

minor correction - the 15" retina MacBook pro is 2880x1800. The 13" retina MacBook pro is 2560x1600.

I was just continuing with the comparison in taneq's post.

Personally, I noticed the (admittedly very minor) improvement going from ~245 ppi to to ~260 ppi, so I doubt I'd have missed a much larger jump, but what's true for me isn't necessarily true for everyone else.

Up to about 300 ppi (maybe even 400 ppi), it’s still possible for someone with good vision to notice a difference at 24 inch viewing distance. I can tell the difference too. If I bring my face to 8 inches from the display, I can notice up past 600 ppi.

But being able to notice something isn’t the same as benefiting in a substantial way. 300 ppi is well past the point of diminishing returns for a laptop. If there were no competing trade-offs, having a 300 ppi display on desktops, a 400 ppi display on laptops, and a 600 ppi display on phones would be great. I just don’t think they’re worth it in return for a big hit on performance and battery life.

Apple’s choice to take early-2000s ~100–120 ppi resolutions and just double them all (using a 2x mode for legacy software support) got them to IMO just about the current sweet spot for PC displays.

The immediate next things to improve in displays are bit depth (12 bit/channel), dynamic range, frame rate (120 Hz? variable?), maybe color gamut (personally I wish we could get more than 3 primaries to widen the color gamut while avoiding spectrum spikiness, but there’s a big content chicken–egg problem), and power use (I want a laptop with 2 day battery life).

In a decade, more software will be properly designed to handle arbitrary-resolution UI, integrated GPUs will be beefier, display protocols will support higher resolutions and framerates, and it will maybe make sense to hop up to 300+ ppi PC displays.

To be clear, I'm not saying that everyone should use 300 ppi displays, or that everyone would benefit. But you need to remember this goes both ways. Not everybody cares about battery life. Some people want 5 hours, and everything above that is superfluous. Some people basically never even unplug their laptops. Not everybody cares about the performance difference; as long as it renders browsers and office apps, it's fine. Others want 4k because it's a pixel doubled 1080p, and they like gaming at 1080p. Some people never even use the built-in monitor. There is no single, homogeneous sweet spot.

I agree that there are other useful steps. OLED laptops are happening, though scaling slowly. 144hz, variable framerate laptops are happening, and are set to completely take over the gaming laptop segment. Touch screen happened. Power efficiency is improving, a recent step being IGZO. It's not like these other aspects are being ignored.

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