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If you look at a printer, it's usually rated at either 300 DPI, 600 DPI
or 1200 DPI. So how many DPI do you get for a typical monitor?
To be completely precise, let's look at *pixels* per inch, since this is
unambiguous.
Now, if I understand this correctly, a 14 inch monitor is actually 14
inches across the diagonal. That means that the 14 inches is the length
of the hypotenuse of a right-angle triangle. Assuming the monitor is 4:3
aspect, we have a 3,4,5 triangle. Based on this, we have:
14" 4:3 = 11.2" x 8.4"
21" 4:3 = 16.8" x 12.6"
Suppose our hypothetical monitor can display 1280x768 pixels. Then in
the horizontal direction, we have:
1280 pixels / 11.2 inches = 114.3 pixels/inch
1280 pixels / 16.8 inches = 76.19 pixels/inch
That's quite some variation. Hmm, let's try my actual monitor at home.
Its resultion is the obscure figure 1680x1050, and it has the weird
aspect ratio 16:10.
Apparently a triangle with sides of 16 and 10 has a hypotenuse who's
length is equal to twice the square root of 89 - or approximately 18.87.
That gives me screen dimensions of about 17.81" by 11.3". And so, we have:
1680 pixels / 17.81 inches = 94.329 pixels/inch
In conclusion, it appears that most if not all current computer monitors
have a density slightly above or below 100 pixels/inch. That's about
tree times lower than the crappiest printer.
Now, admittedly, for colour images computer screens have the advantage
of not requiring the halftoning that printers generally require. But for
black text on a white background, printers win by a mile. (Even
including the fact that computer screens can do antialias, which is
generally a waste of time in printed text.)
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> In conclusion, it appears that most if not all current computer monitors
> have a density slightly above or below 100 pixels/inch. That's about tree
> times lower than the crappiest printer.
My laptop is about 150 dpi, can be a bit small to read on occasion, but I
like having the high resolution. Mobile phones can have 200+ dpi (some even
300 dpi).
> Now, admittedly, for colour images computer screens have the advantage of
> not requiring the halftoning that printers generally require. But for
> black text on a white background, printers win by a mile. (Even including
> the fact that computer screens can do antialias, which is generally a
> waste of time in printed text.)
Also the fact that you usually don't look at your monitor as closely as you
read a printed sheet. The fact that people use mobile phones much closer
has driven them to higher dpi displays. For computer monitors there is
little benefit to going above 100-150 dpi as you simply sit too far away to
notice any higher.
It's like those people that buy a 37" 1920x1080 full-HD TV and then sit 10
metres away from it and claim "I don't see any difference". IIRC your eye
can resolve down to about 1/60 of a degree, so you can do the maths...
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> My laptop is about 150 dpi, can be a bit small to read on occasion, but
> I like having the high resolution. Mobile phones can have 200+ dpi
> (some even 300 dpi).
The idea is that as you increase the number of pixels on the display,
you increase the number of pixels per character as well, so the apparent
text size doesn't alter, but the clarity does.
Unfortunately, I don't know of any system which actually does this. So
turning up the resolution just makes everything smaller and harder to see...
> Also the fact that you usually don't look at your monitor as closely as
> you read a printed sheet. The fact that people use mobile phones much
> closer has driven them to higher dpi displays. For computer monitors
> there is little benefit to going above 100-150 dpi as you simply sit too
> far away to notice any higher.
Well, I've got a sheet of printed paper. The same document appears
somewhat larger on my screen, and yet, holding the paper against the
monitor, the text on the paper is still clearer - despite being smaller.
(Part of this is no doubt due to the screen being emissive while the
paper is reflective, but still...)
> IIRC
> your eye can resolve down to about 1/60 of a degree, so you can do the
> maths...
Apparently 1/60 degree is 1 minute of arc, the sine of which is about
0.0002909. So at 40cm distance, that's... 116.4 um, which is obviously
nonesense.
Damn, I fail trigonometry. :-(
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> Unfortunately, I don't know of any system which actually does this. So
> turning up the resolution just makes everything smaller and harder to
> see...
Ermm Windows does (you can tell it your monitor DPI in display settings
somewhere), I used this setting for ages on my laptop, but then I got a new
CAD program and it didn't like the higher DPI settings so I had to go back
to the defaults.
>> IIRC
>> your eye can resolve down to about 1/60 of a degree, so you can do the
>> maths...
>
> Apparently 1/60 degree is 1 minute of arc, the sine of which is about
> 0.0002909. So at 40cm distance, that's... 116.4 um, which is obviously
> nonesense.
How come? 116um sounds the right order of magnitude for a pixel pitch to me.
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>> Unfortunately, I don't know of any system which actually does this. So
>> turning up the resolution just makes everything smaller and harder to
>> see...
>
> Ermm Windows does (you can tell it your monitor DPI in display settings
> somewhere)
Really? That's interesting...
> I used this setting for ages on my laptop, but then I got a
> new CAD program and it didn't like the higher DPI settings so I had to
> go back to the defaults.
Hahaha... The irony! The one program you'd expect to make use of such
information.
>>> IIRC
>>> your eye can resolve down to about 1/60 of a degree, so you can do
>>> the maths...
>>
>> Apparently 1/60 degree is 1 minute of arc, the sine of which is about
>> 0.0002909. So at 40cm distance, that's... 116.4 um, which is obviously
>> nonesense.
>
> How come? 116um sounds the right order of magnitude for a pixel pitch to
> me.
Isn't 116um less than the wavelength of visible light?
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> Hahaha... The irony! The one program you'd expect to make use of such
> information.
Yeh, some dialog boxes had "OK" buttons outside of the visible area of the
window :-) I guess they don't expect you to be using it on a 15" monitor
running at 1920x1200 resolution - more likely a 22" jobby with the standard
dpi settings.
> Isn't 116um less than the wavelength of visible light?
I think you're confusing um and nm :-) My ruler here has 500 um divisions
clearly marked, I estimate the width of the line used for the markings is
about 100 um, it's clearly visible with the naked eye...
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>> Isn't 116um less than the wavelength of visible light?
>
> I think you're confusing um and nm :-) My ruler here has 500 um
> divisions clearly marked, I estimate the width of the line used for the
> markings is about 100 um, it's clearly visible with the naked eye...
So is a 1nm object, if you have a sufficiently powerful microscope. :-P
So 100um might be visible from 40cm away then?
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Invisible a écrit :
> So 100um might be visible from 40cm away then?
Depending on your sight, I suppose :-)
100µm is also the order of magnitude for the thickness of a hair, and I
can easily see one from 40cm away.
--
Vincent
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Invisible wrote:
> To be completely precise, let's look at *pixels* per inch, since this is
> unambiguous.
Almost unambiguous. Is a pixel one color or three? Screens and cameras, for
example, usually use different definitions for these. Typography software
sometimes takes advantage of the fact that a "pixel" is three picture elements.
> black text on a white background, printers win by a mile. (Even
Generally, 300DPI is considered "proof quality" in printing. It's what you
look at to check for spelling mistakes.
--
Darren New, San Diego CA, USA (PST)
I ordered stamps from Zazzle that read "Place Stamp Here".
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>> To be completely precise, let's look at *pixels* per inch, since this
>> is unambiguous.
>
> Almost unambiguous. Is a pixel one color or three?
I deliberately chose "pixel" rather than "dot" because I didn't want to
count seperate RGB subpixels. :-P
>> black text on a white background, printers win by a mile. (Even
>
> Generally, 300DPI is considered "proof quality" in printing. It's what
> you look at to check for spelling mistakes.
Can't say I really notice a huge difference for plain text printed at
different resolutions - then again, maybe it depends how crispy your
paper is...
--
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*
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