Rationale for 254 ppi pixel density on M-series MBP's?

[theorist9]

Honestly what I keep taking away from your arguments is that there must have been some motive for Apple to go with this density. And my simple answer is that there isn’t one that you will be able to point to that isn’t some variation of “this number seems special”. It isn’t a special number is really the crux of what I’m trying to get at, Apple didn’t do any big revisit here. Apologies if that’s not persuasive evidence, but it’s not like we can dig into the negotiations that Apple had with LG.

I did mention “~127” when I started replying. Yes, I know it isn’t exact, and it’s not 129 px/inch either, it’s 128.65 if we want to get really pedantic about it, putting the exacting display Apple would want at 257.12 px/inch.

Honestly, I imagine the discussion between LG and Apple going a bit like this (only more complicated, because contracts, etc):

Apple: Hey, LG, we need a panel that‘s roughly X px/inch for this display we are working on, what can you do?
LG: Well, we’ve got these options, and here’s what the yields will likely look like, and here’s the startup costs and per sheet costs for each since it’s not something we already do.
Apple: Option Y looks like a good balance, let’s do that.

I would be surprised if it was more complicated than “close enough, low enough startup costs”.

Well, if you'll allow me my own pedantry , 1680x1050 @ 15.4" actually is 128 to 129, and not 128.65 or 127, at least in my world. Apple gives the diagonal to only three significant figures, which means you can only calculate the ppi to 3 significant figues as well. You have no information beyond that. That's why you can only meaningfully express it as 128 - 129 rather than 128.65 or 128.6451972.... However, you do have enough info to say it's not 127—assuming you can rely on the diagonal being 15.4" and not 15.3" or 15.5", which seems reasonable given they're expressing it to the tenths of an inch. Specifically, 15.4" should mean 15.35" – 15.44", which means the possible range is 128–129 ppi.

Also, it's never necessary to say "about" 129 when it comes to measured numbers (as opposed to counted numbers, like 129 oranges), since such numbers are never exact. I do often add the redundancy of "≈"129 on this site, since I know many don't understand that. But I figured you for a technical type for whom such redundancy would be unnecessary.

As to the reason, unless they used an RNG, there's always a reason. I figured, to use your picture, that the conversation with LG went something like this: "Well, we want to replicate about the UI size we get with 1680x1050 @ 15.4", with 2x scaling." "OK, that's a pixel pitch of 98.7 microns; how about we set it to 100 microns?"

I don't know why I'm getting the pushback on this (it's OK--I just don't understand it). E.g., suppose you heard this conversation in Europe: "That's odd—why does this bag of flour imported from the States weigh 454 g? Seems they'd just use 450 or 500." "Ah, that's probably because they package it in pounds, and 1 lb = 454 g". Would you argue against that answer the way you're arguing against what I'm suggesting, saying we can never know what negotations went on between the flour vendor and flour supplier, etc...?

I'm not saying this is *definitely* what happened. What suprises me is that non one (with one exception) has been willing to even acknowlege it sounds plausible. Oh well....

 

[mr_roboto]

So explain why the 27" 5K panels made by LG for the Ultrafine series had notoriously poor yield and quality control problems? I don't get why you think any density panel is possible simply if "people ask for it", when clearly large high density panels are difficult to manufacture.

Can you provide any citations for that? If yield and QC were ever notoriously horrible on those panels, this is the first time I've heard of it.

What I have heard of is people complaining about other quality issues with the Ultrafine 5K, like the creaky cheap plastic housing. I own one myself and don't much like that, or the quality of its AR coating compared to the 27" retina iMac displays. The panel itself seems fine, and it is almost certainly the same panel Apple uses in its 27" 5K displays, or perhaps a slightly worse grade of it (LG is Apple's supplier for 27" 5K).

Also, several iPhone models had 326ppi LCDs. So clearly, higher than 250 isn't a huge problem. (The power issues I cited as a reason to avoid going lots higher aren't as relevant at the scale of phone displays - backlight power also scales with total panel area.)

@theorist9 , would disagree with you. They seem to be convinced that the limit of human vision is 500 or 1000 ppi, and they don't seem to acknowledge the diminishing returns argument which I also made.

I doubt that's what they meant, and more importantly this is something which varies based on context. There are tons of phones in the 300-500ppi range, but essentially no laptops. That's because people often hold their phones much closer to their eyes, so going over 300 actually makes a substantial difference.

 

[Mr Screech]

I like the sound of 100 pixels per cm standard, maybe apple's pushing for a shift to the superior metric system.

 

[Krevnik]

As to the reason, unless they used an RNG, there's always a reason. I figured, to use your picture, that the conversation with LG went something like this: "Well, we want to replicate about the UI size we get with 1680x1050 @ 15.4", with 2x scaling." "OK, that's a pixel pitch of 98.7 microns; how about we set it to 100 microns?"

Based on my time in the industry, I suppose you could say that there is always a reason so long as things like "It was that way when I found it" or "someone didn't think something through years ago and now we don't want to change it" is considered a valid reason. But good luck getting companies to acknowledge that in public, but it's probably the most common thing I keep hitting in corporate engineering on anything with any legacy longer than 6 months.

But I guess I don't attribute areas where a company clearly didn't place importance as something the engineers reasoned about. Precisely because the lack of importance meant time and effort was spent elsewhere instead.

I don't know why I'm getting the pushback on this (it's OK--I just don't understand it). E.g., suppose you heard this conversation in Europe: "That's odd—why does this bag of flour imported from the States weigh 454 g? Seems they'd just use 450 or 500." "Ah, that's probably because they package it in pounds, and 1 lb = 454 g". Would you argue against that answer the way you're arguing against what I'm suggesting, saying we can never know what negotations went on between the flour vendor and flour supplier, etc...?

I would not be arguing against that, but I don't agree it's a similar analogy.

I'm not saying this is *definitely* what happened. What suprises me is that non one (with one exception) has been willing to even acknowlege it sounds plausible. Oh well....

For my case, it's because I've been in the industry long enough to be jaded by how corporate engineering works. These are effectively mundane details at this point, and the engineers are focused in other areas like Mini-LED.

But also keep in mind it started with the hypothesis that Apple might be going to a higher density on the XDR, which I think we've at least established seems unlikely.

 

[tornado99]

Can you provide any citations for that? If yield and QC were ever notoriously horrible on those panels, this is the first time I've heard of it.

I don't have a neat link, just observations from various forums over the years. Also the large number of 'A-' and 'B' grade panels sold on Aliexpress for people doing DIY repairs or building their own 5K monitors. And for a short time Iiyama and some American company tried to bring 5K to the mass market with same/similar LG panel, but suffered even worse QC (ProLite XB2779QQS).

To be fair though, perhaps a lot of that was the challenges of backlighting such a large area evenly, rather than problems with the LC array itself. (Edit: but then it doesn't seem to have affected 27" 4K which are ubiquitous).