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Once Again. Maybe This Time You'll Get It Straight: Scanner Scaling

 
 
hydra
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      12-24-2003
A lot of people up here talk about DPI, PPI, etc., but they never talk
about THE SIZE OF THE OUTPUT IMAGE. This is of course of
fundamental importance because we don't really want to print
useless output image sizes by just following the dpi and the ppi
numbers.
Here is a concrete situation. I hope that it is clearer for everybody
now.

I scan an image at 72 dpi with output at 1024 horizontal pixels.
The scanner automatically scales the output image to 1024 pixels,
or somethiing close to that.

Then I scan the same image at 300 dpi with output image again
at 1024 horizontal pixels. Again, the scanner will automatically
scale the output image to 1024 pixels or something close to it.
Which of the two H1024 images is better?

Example:

Input Image: 72 dpi W419 H284 (Output Image: the same, Scale 100%)
Output Image: 72 dpi W1023 H693 (Scale 244%) (no. 1023 set by
myself)

Input Image: 300 dpi W1749 H1185 (Output image the same, Scale 100%)
Output Image: 300 dpi W1023 H687 (Scale 58%) (no. 1023 set by
myself)

Thank you!

phaethon

 
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Jim Townsend
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      12-24-2003
hydra <> wrote:

> A lot of people up here talk about DPI, PPI, etc., but they never talk
> about THE SIZE OF THE OUTPUT IMAGE. This is of course of
> fundamental importance because we don't really want to print
> useless output image sizes by just following the dpi and the ppi
> numbers.
> Here is a concrete situation. I hope that it is clearer for everybody
> now.
>
> I scan an image at 72 dpi with output at 1024 horizontal pixels.
> The scanner automatically scales the output image to 1024 pixels,
> or somethiing close to that.


Whoa.. You're the one who mentioned that people don't talk about the size of
the output image.. Lets talk about the INPUT image. The size of the document
you're laying on the scanner and scanning. You don't seem to think this is
important enough to even mention.

How BIG is the image you're scanning. You've indicated that you've set your
scanner at so-many-dots-per-inch.. Consider the term 'inch'. Now tell me,
INCHES OF WHAT ?

I'm going to bring up a couple of points..

If you scan a one inch wide image at 300 dots per inch, would it not be logical
to assume you would derive 300 horizontal dots from the scan ?

Going further, could you not expect a 6 inch wide image to have 6 inches x 300
dots per inch = 1800 dots.

Would it not be logical that the larger the image, the more dots you get.

Please explain how the above three points could be wrong.


> Then I scan the same image at 300 dpi with output image again
> at 1024 horizontal pixels. Again, the scanner will automatically
> scale the output image to 1024 pixels or something close to it.
> Which of the two H1024 images is better?


Again.. How BIG is the image you are scanning.

> Example:
>
> Input Image: 72 dpi W419 H284 (Output Image: the same, Scale 100%)
> Output Image: 72 dpi W1023 H693 (Scale 244%) (no. 1023 set by
> myself)
>
> Input Image: 300 dpi W1749 H1185 (Output image the same, Scale 100%)
> Output Image: 300 dpi W1023 H687 (Scale 58%) (no. 1023 set by
> myself)
>
> Thank you!
>
> phaethon


 
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Annika1980
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      12-24-2003
>From: ">hydra <>

>I scan an image at 72 dpi with output at 1024 horizontal pixels.
>The scanner automatically scales the output image to 1024 pixels,
>or somethiing close to that.
>
>Then I scan the same image at 300 dpi with output image again
>at 1024 horizontal pixels. Again, the scanner will automatically
>scale the output image to 1024 pixels or something close to it.
>Which of the two H1024 images is better?


They are equivalent.
You now have two files of equal size.
dpi means nothing until you print.




 
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hydra
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      12-24-2003
On Tue, 23 Dec 2003 22:20:16 -0600, Jim Townsend <(E-Mail Removed)>
wrote:

>hydra <> wrote:
>
>> A lot of people up here talk about DPI, PPI, etc., but they never talk
>> about THE SIZE OF THE OUTPUT IMAGE. This is of course of
>> fundamental importance because we don't really want to print
>> useless output image sizes by just following the dpi and the ppi
>> numbers.
>> Here is a concrete situation. I hope that it is clearer for everybody
>> now.
>>
>> I scan an image at 72 dpi with output at 1024 horizontal pixels.
>> The scanner automatically scales the output image to 1024 pixels,
>> or somethiing close to that.

>
>Whoa.. You're the one who mentioned that people don't talk about the size of
>the output image.. Lets talk about the INPUT image. The size of the document
>you're laying on the scanner and scanning. You don't seem to think this is
>important enough to even mention.
>
>How BIG is the image you're scanning. You've indicated that you've set your
>scanner at so-many-dots-per-inch.. Consider the term 'inch'. Now tell me,
>INCHES OF WHAT ?
>
>I'm going to bring up a couple of points..
>
>If you scan a one inch wide image at 300 dots per inch, would it not be logical
>to assume you would derive 300 horizontal dots from the scan ?
>
>Going further, could you not expect a 6 inch wide image to have 6 inches x 300
>dots per inch = 1800 dots.
>
>Would it not be logical that the larger the image, the more dots you get.
>
>Please explain how the above three points could be wrong.
>
>
>> Then I scan the same image at 300 dpi with output image again
>> at 1024 horizontal pixels. Again, the scanner will automatically
>> scale the output image to 1024 pixels or something close to it.
>> Which of the two H1024 images is better?

>
>Again.. How BIG is the image you are scanning.
>
>> Example:
>>
>> Input Image: 72 dpi W419 H284 (Output Image: the same, Scale 100%)
>> Output Image: 72 dpi W1023 H693 (Scale 244%) (no. 1023 set by
>> myself)
>>
>> Input Image: 300 dpi W1749 H1185 (Output image the same, Scale 100%)
>> Output Image: 300 dpi W1023 H687 (Scale 58%) (no. 1023 set by
>> myself)
>>
>> Thank you!
>>
>> phaethon


Jim,

Whatever you are saying does not take into consideration the scanner
scaling. Where exactly is the scaling in your 3 points above? The
whole question has to do with the subject of scaling. My question was:
if we scale the picture to H1024 with 72dpi and 300dpi, which one
is a better picture? Remember, the scaling by the scanner is more
involved than just cutting horizontal and vertical lines.
And, the input image dimensions at 72 dpi and 100% scaling do tell you
how large the input picture is, don't they? Think about it.
By the way, I AM a mathematician. What math would you like?
Algebra, Analysis, Topology, or Probability Theory?
Thank you for your time and interest.

phaethon
 
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