Screen Size and Resolution- Daniel
Knight, November 19, 1999
I have yet to see a 15" monitor that looks crisp at
1024x768, or even a 19" one that does justice to 1280x960 or
1280x1024 resolution. Yet these monitors are often rated for these settings,
and often even higher ones. What's going on here? Quite simply, we're looking at the difference between how
many dots per inch the computer is trying to display and how
many dots per inch the monitor can show before they start
running into each other. A decent monitor today will have a horizontal dot pitch
of about 0.22 mm. That is about 4.5 dots per millimeter or
115 dots per inch. Anything higher than that will be fuzzy,
since the monitor will be trying to display more than one
pixel per screen dot.
(For more on dot pitch, see Monitor
Dot Pitch.) My 19" Optiquest V95 monitor has an image about 13.5"
wide, so it should be able to crisply display 1550 pixels at
one per dot. Yet if I set it to 1600x1024, it's fuzzy. And
even if step back to 1280x960 or 1280x1024, it's still
fuzzy. Yet 1152x870 seems crisp. Weird, isn't it. Obviously, there's more to crisp display than simple dot
pitch and resolution would indicate. That doesn't mean that
dot pitch isn't a good indicator of screen sharpness, only
that it doesn't directly predict with the maximum sharp
display setting. In reality, you have to be at 1-1/3 to 1-1/2 dots per
pixel before the screen looks pretty sharp. In the case of
my Optiquest, that explains why 1280 dots horizontally
doesn't quite cut it, but 1152 works very nicely. Looking at another example, while my 17" Nokia 447z was
in the shop (now for the third time) and before I picked up
the Optiquest, I used a 15" Compaq Presario v410 monitor. It
claimed to support some high resolutions, but the highest
one that looked sharp was 832x624. The Presario has a dot pitch of 0.28, which comes to
about 0.22 horizontally. It can display a fuzzy 1024x768.
Again, a 10.5" horizontal dimension predicts a sharp 1200
dots, but it just doesn't work out in the real world. Instead, we seem to be at that ratio of about 1.4 dots
per pixel for a sharp display. And the same goes for the
iMac, which looks great at 800x600, but fuzzy at
1024x768. Studies have shown that when scanning images for printed
output, the image should be scanned at 1-1/3 to 1-1/2 times
the final resolution -- or it will look fuzzy. The same
principle is at work here. As a general rule of thumb, a good monitor will have a
horizontal dot pitch of somewhere around 0.22 (or a diagonal
dot pitch of 0.25-0.28). Using the square root of 2 (1.414)
as our factor, to achieve a specific sharp resolution, you
must have a monitor of a minimum size.
resolution | screen size | 640x480 | 7.9"x5.9" (9.9" diagonal) | 800x600 | 9.8"x7.4" (12.3" diagonal) | 832x624 | 10.3"x7.7" (12.9" diagonal) | 1024x768 | 12.6"x9.5" (15.8" diagonal) | 1152x870 | 14.2"x10.7 (17.8" diagonal) | 1280x960 | 15.7"x11.8" (19.6" diagonal) |
Keep in mind that this is viewable area, not the full
size of the picture tube, and that this assumes about 0.22
horizontal dot pitch. This helps explain why a modified
Color Classic can just
support 640x480 with some hardware hacking (it has a
viewable area just over 9"), but the iMac's
13.8" viewable screen isn't sharp at 1024x768 -- it's two
inches too small. My old Nokia monitor worked fine at 1024x768, but simply
didn't look good at any higher setting. My Optiquest 19" is
great at 1152x870, but doesn't quite cut it as 1280x960. Yet
the Sony monitor I use at work, a 21" screen, supports
1280x960 beautifully. How I WorkI spend a lot of time switching between Claris Emailer,
Claris Home Page, my browser (usually Internet Explorer 4.5,
but sometimes Netscape 4.7 or iCab 1.7), and a shareware URL
manager called WebChecker. I find it works best if I keep
Emailer on the left of the screen at about 600 pixels wide
and nearly full screen height, WebChecker on the right at
close to full screen height (I visit a lot of sites daily),
and move the browser and Home Page windows as necessary.
Much of the time I'm moving between Home Page and my
browser, so it's nice if those windows can be next to each
other with little or no overlap. Because I try to design my site to work well even on
older Macs (and PCs) with smaller screens, I keep my browser
window at about 640 pixels and set my Home Page preview to
640x480. To work side-by-side, that calls for a 1280x960
monitor. That's what I have at work, and I love it. But at home, until a few weeks ago I was living with
832x624 (or 1024x768 when the Nokia worked), which meant a
lot more overlap between the windows. Not only does this
look cluttered, but it takes longer to switch between
applications when more of the screen needs to be
redrawn. Much as I'd love a 21" screen, they're pretty expensive.
But when deal-mac pointed to the Optiquest 19" at $340, I
jumped. (I paid about $450 for my 17" Nokia 1-1/2 years
ago.) I've discovered 19" is a bit less than I'd like, but it
is a huge improvement over 1024x768. There's a little
overlap, but a lot less than there was. And with a little
creative resizing, I can have my browser window and Home
Page windows next to each other. In fact, the main obstacle to my using an iMac is the
need for such high resolutions for the kind of work I'm
doing. I could work smaller, but below 1152x870, I lose
efficiency. Your work habits will determine how much screen you need.
And once you know that, you can use the table above to
decide the minimum viewable area you need to get it. What About LCDs?About now, some of you may be wondering, "What about
laptops? Do they suffer from the same problems as
conventional monitors?" Happily, the answer is no. A dot on a flat panel display
is a dot. Period. In fact, flat panel displays will look
fuzzy at any setting other then their maximum. A PowerBook
G3 with a 14.1" 1024x768 screen is a thing of beauty,
but 800x600 and 640x480 look fairly bad. Likewise, the
iBook looks great at
800x600, but simply isn't crisp when displaying 640x480. - The only ways to have sharp resolutions other than
the maximum are for the maximum to be an exact integer
multiple of the lower resolution (e.g., a 1280x960 screen
displaying 640x480) or to only use a portion of the
display to show the lower resolution.
This gives flat panel displays several advantages over
traditional monitors, along with two disadvantages. Advantages- tack sharp at their designed resolution
- smaller display remains sharp (14.1" diagonal
provides a sharp 1024x768, where a CRT must have a
viewable diagonal of at least 15.8")
- smaller footprint
- very low power consumption
Disadvantages- fuzzy at any resolution other than the maximum (with
rare exception of exact integer multiples)
- expensive
For now, traditional monitors are the way to go unless
you need portability or have a generous budget. But over
time flat panel displays will continue to drop in price and
increase in resolution. In fact, IBM recently shows screens
that displayed 123 points per inch -- that beats the 0.22
horizontal pitch of today's good monitors, and it's tack
sharp at that setting. The day Apple announces a PowerBook with a 1280x960
screen is the day I prepare to retire my huge desktop with
it's big 19" monitor. With IBM's new technology, that
PowerBook could have a 13" display with 1280x960
resolution. In fact, I'd consider making the move to a PowerBook if
Apple had an 1152x870 display -- even if it measured 14" or
15" diagonally.  Recent articles on Online Tech Journal
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