Working with Images

[David Creamer]

On Dennis Brunnenmeyer at dennisb at chronometrics.com wrote on 2/5/08 11:36
AM:

> Rant begins...
> <snip>
> 
> First of all, display devices, whether printers or monitors, have an upper
> limit on their ability to resolve (print or display) image detail, which by
> the way is what "resolution" is a measure of...meaningful detail. The best my
> aging but faithful laser printer can do is 600 dpi, while my uppity LCD
> monitor can display up to 100 dpi, with its1600 x 1200 native resolution on an
> LCD panel that is exactly 16" wide x 12" tall."
You are totally ignoring line screen (aka LPI) when printing. Using the
formula will determine the quality of the output on a black-only laser
printer:
(Output Resolution/Screen Frequency)^2 [squared] +1 = total number of gray
levels available to the printer.
So a 600dpi printer at 100 LPI gives you only 37 levels of gray. For photos,
you need around 200 levels of gray to look natural.

For commercial offset printing, one should use the following guideline:
PPI= LPI x 1.5. (Some use LPI x 2, but 1.5 is normally enough.)

> You cannot see nor capture
> anything and create a screenshot image with higher resolution than the display
> device......
I think I said something similar to that.

> 
> Most of you seem to appreciate this, but some of you think you can improve
> resolution by artificial means. No, you cannot.
I think I said something similar to that.
> 
> A true measure of the resolution of an image is the original size of the image
> in total pixels, assuming it is true to begin with.
I think I said something similar to that.
.....

>[Unfortunately, since the graphics card's resolution doesn't
> match the native resolution of the LCD panel, the on-screen picture is not as
> crisp as it could be. This is a result of "aliasing" artifacts, but that's a
> topic for a different thread.]
I believe you are confusing what you see on screen to what is actually being
captured.
> 
> 
>..... If I set the capture "resolution" to 160 ppi, then the
> image will be half the physical size as it appeared on the screen, BUT IT WILL
> HAVE EXACTLY THE SAME NUMBER OF PIXELS. The resolution has not be improved, as
> no more detail has been added.
I think I said something similar to that.
> 
>.... No new detail nor
> image improvement can be added by interpolation.
I think I said something similar to that.
However, I suspect you have not used nearest neighbor interpolation too
much.

> 
> I have no idea what David meant by this statement:  "Again, referring to my
> last post, monitor resolution only counts if
> capturing an entire screen."
I thought it was pretty clear. 1280x1040 is the same amount to X/Y pixel
data on a 17 inch monitor, a 19 inch monitor, or a 20 inch monitor.
> 
> Flame away...
I try not to flame or rant as I think it dilutes the message and reflects
poorly on the messenger

David Creamer
I.D.E.A.S. - Results-Oriented Training
http://www.IDEAStraining.com
Adobe Certified Trainer & Expert (since 1995)
Authorized Quark Training Provider (since 1988)
Markzware, Enfocus, FileMaker Certified