DPI: TRUTH OR LIE?

[mgeduld]

Figure 5:

[michaelward]

and explained that really well!

Simple as:

Use pixels as a measurement for the web, and forget DPI.

Uses inches as a measurement for print work, and set the appropraite DPI for your output (ie 600dpi if your printer is 600dpi)



Michael Ward
http://LeighCenturions.net

[Klaus Nordby]

Guys, now you're finally getting what I have been saying all along!

No DPI for screen/web, lots of DPI for print.

Welcome to the club - but I fear it's still a small fraternity! I estimate that only 5% of all designers understand these things - and only 2% of all SB-people (who are even dumber than designers).


K
www.klausnordby.com/xara

[Klaus Nordby]

Egg: "Another point worth mentioning is the difference between CRT monitors and TFT monitors. I don't pretend to understand the difference but I believe a TFT monitor is set a particular resolution, and whilst it can copy other resolutions it does it differently and far worse than a CRT screen"

Your observations are all correct. The difference between CRT (regular, oldstyle monitors) and TFT/LCD (notebooks and newfangled flatpanels) is simple, and explains why the image on LCD monitors so often look "far worse" when you change the screen's pixel area settings. (I use the term "screen's pixel area" instead of the term "screen resolution" since this is a total misnomer only spreading confusion about the nature of "resolution.") CRT tubes do not have a fixed screen pixel area at all, whereas LCD panels do. The screen pixel area of a CRT is wholly created by the graphics card, it is only limited upward to whatever is the maximum number of horiz/vert pixels the tube can handle. So CRTs have a "fluid" nature, with no number of horiz/vert. pixels being more "right" than any other: it just accepts with no problems whatever screen pixel area the graphics card throws at it. But LCDs have a built-in fixed grid of pixels - an actual physical screen pixel area, like 1024x800. So if you change your graphics cards screen pixel area from the factory set default 1024x800 to, say, 600x800, there is no longer any 1:1 correspondence between the panel's rigidly locked physical characteristics and the information generated by the graphics card. The screen must therefore remap the screen pixel area to the physical pixels - and this must inevitably result in jagginess. Some single screen area pixels will be spread from one to cover two LCD pixels, and others will be squeezed down from two pixels to one. In LCDs, there are no in-between "decimals", only "integers".

So for people who like to switch between different screen pixel area settings all the time - like we designers do a lot - LCDs are a very poor choice. Personally, I go crazy when I see remapped pixels on any screen! So if we want maximum monitor quality, we're stuck with huge, bulky CRTs for - God knows how long.


K
www.klausnordby.com/xara

[Klaus Nordby]

Marcus: "Filesize is determined by number of pixels -- NOT by dpi."

True - but it's not ONLY determined by the number of pixels, but by the number of pixels and theCOLOR DEPTH of the image: 1-bit, 8-bit, 24-bit, 32-bit etc. These are of course global values: all pixels in an image must have the same same color depth - the color depth can't vary in different pixels. A small but important point to fully understand a file's size in working memory.

When saved on a disk or transmitted via the Net, there is of course no correspondence between a file's size in working memory and its stored/transmitted size. Hence, that small 60 Kb JPG file we download may well swell to 10Mb when viewed in a browser - and thus bring a system with little RAM to its knees! (Impossible, you say? I have such a file open right now.)

Gee, there's something about this entire resolution/file size/color depth thing which really fascinates me! :-)


K
www.klausnordby.com/xara

[michaelward]

I think we're now wandering away from the (hopefully resolved) issue at hand... DPI for the web or not.

I think that's where we should stop for this thread.

Full Stop.



Michael Ward
http://LeighCenturions.net

[pduggan]

<BLOCKQUOTE><font size="-1">quote:</font><HR>I think that's where we should stop for this thread.<HR></BLOCKQUOTE>

Come on, Michael — stop trying to play God! It's just starting to get really interesting with Klaus's latest observations about CRTs, TFT/LCDs and working memory (and I mean that, Klaus)...

Peter</p>

Peat Stack or Pete's Tack?</p>

[michaelward]

Well I should smite you down right were you sit!!

[img]/infopop/emoticons/icon_wink.gif[/img]



Michael Ward
http://LeighCenturions.net

[Ross Macintosh]

Yes Klaus, what's this thing about small k images consuming huge amounts of system resources??

And someday we'll have to get you guys to work explaining optimal scanner settings. That subject really seems to be beyond comprehension to so many scanner owners.

Regards, Ross

<a href=http://www.designstop.com/>DesignStop.Com</a>

[michaelward]

I hate scanners that interpolate, and it's nigh on impossible to find their optical resolution.



Michael Ward
http://LeighCenturions.net