No. 300 DPI printing is not the same as 300 DPI on screen, because one dot on screen can be multiple colors (depending on the color depth, typically 16,777,216 can be expected), while one dot on paper is, well, either black or white. So for the same DPI, screen outperforms paper. 250 DPI on screen will definitely beat 300 DPI on paper.
It's not quite as clear as that. People aren't confusing DPI and PPI -- they're the same thing. Pages like the linked that suggest otherwise are muddying the problem, because they're misunderstanding how printing works by ignoring line screening and halftoning.
A 300ppi screen that fits 300 pixels into an inch is exactly the same as a 300dpi printer that can fit 300 dots of its laser into an inch of drum.
The difference comes because screens can directly vary the colour of an individual dot. Printers can't -- ink is either present or it is not. The way you get around that is by varying the size of the dot, in a process called halftoning.
Halftone dots are very small, and are arranged in patterns you'll recognise if you look at newsprint photographs close-up. You measure the size of the screen in LPI -- lines per inch, the number of lines of dots (at max size) that can fit in an inch.
Because of the need to vary the size of the dots, on a 300dpi printer you end up with a very coarse line-screen of about 60 LPI. This looks rotten, and so printers go up to resolutions of 1200+dpi. This means you can have a linescreen of around 150lpi, which is good enough for most printing. Each line roughly equates to 2 pixels, and hence a 300ppi image is sufficient for printing, regardless of the resolution of the image or platesetter.
But this doesn't mean there's a difference in ppi or dpi: they're still exactly the same.
Is that really true in general? I'd say the difference in print start to disappear around 600dpi (dpi/clarity isn't really discernibly different between a 600 dpi print and a 1200dpi print. But up to 600 dpi, I'd say there definitively is a difference)?
Granted, with current technology we have single-coloured pixels, so 300 ppi is really 3-900 dpi (or pixel-parts) -- that might have something to do with it?
> It's easy to see the difference between a page printed at 300 dpi and one printed at 600 dpi
This depends entirely on viewer and viewing distance. 300 dpi should be roughly at the limit of what someone with 20/20 vision can distinguish from a distance of about a foot.
If you get a teenager with 20/15 vision and put them as close as their eyes can focus (say, 4 or 5 inches), they’ll be able to see a clear difference between these. But if you take an average person and look at the two images from a distance of a few feet, it will be all but impossible to tell the difference.
So your argument is that 300 PPI displays are great for processing photos you intend to have printed at 300 DPI. I have no problem with this claim, and I'll extrapolate to "better for >= 300 DPI prints".
So, I guess the obvious question is, how much DPI do various prints come out with? And since almost all electronic displays have far less than 300 PPI, would you agree that web designers do themselves a disservice if they get a high-resolution display?
I'm all for higher DPI screens, but you need to take into account that typical reading distance for screens is larger than for text on paper. It is not really DPI that counts but dots per angular distance as seen from the eye.
People confuse PPI (pixels) and DPI (dots) all the time. Yes, a press might run at a higher DPI than 300, but a 300-400PPI image is generally considered sufficient for even coffee table book-quality printing.
DPI is very different though, a screen sub pixel can vary in luminescence (typically index in most displays with 6bits of accuracy, minus crappy colour gamut on the display) whereas a printed dot is limited to the ink colours used.
Some printers overlap dots, print thicker dots, and have other tricks to work around this aspect. I don't know as much about this area, I've worked mostly in graphics, but my understanding is that because the colour gamut for each printed 'pixel' is less expressive, you need more dots in the same area to get a similar result.
Furthermore, dpi expresses printed 'dots' whereas a pixel on most displays can be considered three fixed 'dots', one for each display channel. Although lately, some LCD substrates are cheating a little and displaying only 2 subchannels per pixel.
Anyways, that's everything I know about dpi, as I said, I'm more versed in video rather than printing. So take this with a grain of salt: I think you need to multiply PPI by 3 to get DPI, ignoring cleverness on the part of either display or printer manufacturers.
Interestingly, in high-end printing, 300 dpi is considered unacceptably poor, most print shops will simply refuse to print artwork at 300 dpi. 600 dpi is usually what's considered minimally acceptable for artwork and around 1200 dpi for lots of text.
They aren't directly comparable, but they are comparable. A 500 DPI printer is going to produce better text on an A4 page than a 1 PPI A4 sized display, right?
Do you think text on your 165 PPI display is as sharp as even a low end laser printer?
But then ink dots are either there or not, you cannot have as many different colors as you can in one screen pixel. So comparing laser printer resolution to screen resolution is not so simple.
A 300 ppi screen is a 1200 sub-ppi screen. Those subpixels are not as versatile as ink dots in some ways (a green subpixel can’t suddenly turn red) but more versatile in other ways (as you already said, a ink dot is either there or not – it can have a few different sizes but it’s arguably easier for a subpixel to change its brightness).
Do those same eye limits apply to printers? A 24” 4k screen is 180 PPI (according to Google). Can you tell the difference between a page of text and images laser printed at 200 dpi and 1200 dpi?
"I care about the dots/pixel"
Yes, but those are two different dots you're talking about. What you actually care about is how many printer dots you get for each image pixel.
There is a distinction, and I'm all for precision in language, but it's nothing more than a language distinction for the sake of clarity.
It is not a technical distinction, is my point, and people like Bray aren't wrong to call this a 300dpi display. The worst you can say is they are slightly less precise in their speech than is optimal.
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