No problem sir, we are all human. Thank you for being a gentleman and replying
to my post.
Rick
_____
From: Dennis Brunnenmeyer [mailto:dennisb at chronometrics.com]
Sent: Wednesday, February 06, 2008 2:11 PM
To: TEI Melanson, Richard; framers at lists.frameusers.com
Subject: RE: Working with Images
Rick...
You are very correct about my brashness. My apologies to all of you. I
was anxious to try and squelch some misconceptions and got carried away. David
Creamer was particularly incensed with me because he thought I was aiming the
whole rant at him. This was not the case, of course, but I can see his point.
in the meantime, he and I have called a truce, as we both have better things to
do.
Dude...
******************************************
At 06:26 AM 2/6/2008, richard.melanson at us.tel.com wrote:
Dude, you may be the expert on this, and the info you supplied
in your response is so good I am saving it, but how about a little respect for
everyone on the list. I believe whatever anyone said in an attempt to help they
believed to be accurate and helpful. To say and I quote you "Well, I've had
enough of this nonsensical babble. None of you seem to understand what you are
talking about when it" is a little strong. Life is too short, take a deep
breath and enjoy!!
Rick
-----Original Message-----
From: framers-bounces at lists.frameusers.com [
mailto:framers-bounces at lists.frameusers.com <mailto:framers-bounces at
lists.frameusers.com> ] On Behalf Of Dennis Brunnenmeyer
Sent: Tuesday, February 05, 2008 2:37 PM
To: David Creamer; framers at lists.frameusers.com
Subject: RE: Working with Images
Rant begins...
Well, I've had enough of this nonsensical babble. None of you
seem to understand what you are talking about when it comes to dealing with
screenshots and raster images, (a.k.a. bitmapped images) as opposed to vector
or llne art.
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 cannot
see nor capture anything and create a screenshot image with higher resolution
than the display device. You cannot print anything with higher resolution than
the printer can resolve. If you feed a high resolution image to a medium
resolution printer, it will interpolate (resample) the image down to medium
resolution quality. It has to, as it cannot put all of that information on
paper. If you take an very high resolution (total pixel count) image of size
4000 x 3000 pixels (12 megapixels) and display the full image it on a monitor
like
mine, you will
not see all of detail in the image and hence you will not be
able to capture all of the detail in a screenshot.
Most of you seem to appreciate this, but some of you think you
can improve resolution by artificial means. No, you cannot.
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. That is,
assuming a perfect digital camera with a perfect lens and the ability to
produce a "raw" bitmap (rather than a compressed JPEG file), that 12 megapixel
CCD image sensor will produce a significant improvement in the resulting image
over a 2 megapixel CCD sensor.
That image quality is NOT described by either ppi or dpi. It is
a function of the number of pixels in the X direction and the number of pixels
in the Y direction.
Now the plot thickens when I return to the subject of
screenshots, because if I run my graphics card at 1600 x 1200, the type, icons
and dialog boxes are uncomfortably small for me to read on the monitor, so I
set the graphics card to display its images at 1280 x 960 dpi.
At this point, the maximum image size that can be displayed
without loss of resolution is now 80 ppi. That's 1280 divided by 16.
[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.]
Note that in the above paragraph, I switched from dpi for
display devices to ppi when describing image size. This is a meature of the
physical size of a digital image (as printed or displayed) and should be
described in ppi. The ability of a device to display or print an image should
be described in dpi, or alternatively, lpi for lines per inch, or pixel
spacing, as in 0.25mm. There is a tendency to intermix this terminology and
hence confuse the issues you are discussing.
Now that I have set my graphics card to 1280 x 960 for this
monitor, the maximum resolution of any image I capture from the screen is 80
ppi, regardless of whether I capture a whole screen or just a region of it. If
I set the "resolution" of the screen capture program (Snag-It or HyperSnap) to
80 ppi, then the resulting image will be the same physical size as it appeared
on the screen, 100%. 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.
Upsampling and/or downsampling using any kind of pixel
resampling (a.k.a. interpolation), whether bicubic or otherwise, ALWAYS removes
detail from the image. In either case, new pixels are created that are some
kind of average of the original ones. They're guesses at what shoud be there at
that point in the image, and not real information that wasn't there before. No
new detail nor image improvement can be added by interpolation.
Now, however, you can re-scale an image in programs like
Photoshop by keeping the same number of pixels (do not interpolate) and
altering the size of the image in the X and Y directions equally. For example,
if I took the 160 ppi screenshot described in the previous paragraph and
re-scaled it in Photoshop without resampling the image, and if I prescribed a
new size of 80 ppi, the resulting image would grow back to 100% in size and
have still have exactly the same number of pixels as before. The resolving
power of the image has not changed, and no more detail has been provided. This
is a correct way to get an image to the size you want it in your document.
Another way is to import it as is and resize it in Frame using the image's
corner anchor points while holding the Shift key down.
Don't mislead yourselves and others by thinking that the more
"resolution" in your screenshot capture application you use gives you better
results, and don't mislead yourselves by thinking you can add more resolution
by upsampling (or rescaling, for that matter) to a different ppi or by adding
more artificial pixels.
Now, on another topic, there seems to be a rule of thumb that
"most SVGA screens are 96dpi." Someone came up with the statement that a 20"
screen with a 1280 x 1024 display is, of course, 96 dpi. That's utter nonsense.
Given that screen size is measured on the diagonal, and assuming the old
standard 4:3 aspect ratio, a 20" screen is 16"
wide and 12" tall...rather like my Samsung LCDs. With 1280
pixels in the X (horizontal) direction, the screen resolution is 80 dpi, not 96
dpi. Any way you manipulate the numbers, 96 dpi is not a result. By the way,
here I assumed a 4:3 aspect ratio, which is the ratio of width to height. If I
ran my graphics card at 1280 x 1024, circles would be egg-shaped, since that
resolution calls for a screen with a
5:4 aspect ratio. Of course, wide screens have a different
aspect ratio, but the principles are exactly the same.
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." Monitor size DOES count if you're trying to calculate the
resolving power of your monitor in dpi and hence the maximum resolution
attainable in a screenshot. It's the horizontal resolution of your graphics
card setting divided by the width of the display area in inches or centimeters,
or in the example given,
1280/16 = 80 dpi.
End of rant ...
Flame away...but be sure you know what you are talking about
and quit misleading others if you don't understand this.
Dennis Brunnenmeyer
***************************************************************************************
At 09:09 AM 2/5/2008, David Creamer wrote:
> > How can SnagIt capture an image at a higher resolution than
what the
> > screen is set to? A 20" screen at 1280 x 1024, for
example, is 96
> DPI. How do you
> > get 200 DPI out of that?
>
>Screen size (20") is meaningless, only the monitor resolution
counts.
>Again, referring to my last post, monitor resolution only
counts if
>capturing an entire screen.
Dennis Brunnenmeyer
Director of Engineering
CEDAR RIDGE SYSTEMS
15019 Rattlesnake Road
Grass Valley, CA 95945-8710
Office: (530) 477-9015
Fax: (530) 477-9085
Mobile: (530) 320-9025
eMail: dennisb /at/ chronometrics /dot/ com
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Grass Valley, CA 95945-8710
Office: (530) 477-9015
Fax: (530) 477-9085
Mobile: (530) 320-9025
eMail: dennisb /at/ chronometrics /dot/ com
