Pixels / inch...

[Steve]

OK, here is a very basic question that I can't quite seem to answer for
myself.

My camera can adjust the number of pixels captured (picture resolution?) and
the data compression setting (image fineness?), but what / when / how is the
number of pixels / inch set? I have a Canon A520 with a maximum resolution
of 2272 x 1704 and all my images seem to get captured at 180 pixels / inch.

Am I missing something? Or should I just start the weekend early in an
attempt to get more R&R?

Thanks, Steve

 

[Guest]

All this depends on the Resolution and size of your moniter.

If you have a 17 inch moniter with 800 by 600 pixels you are going to have a
lower number of pixels per inch. likewise if you have a 14 inch moniter with
1024 by 768 pixels your pixels per inch will be higher.

Hope I helped!

~Usobe

 

[Jim]

OK, here is a very basic question that I can't quite seem to answer for
myself.

My camera can adjust the number of pixels captured (picture resolution?) and
the data compression setting (image fineness?), but what / when / how is the
number of pixels / inch set? I have a Canon A520 with a maximum resolution
of 2272 x 1704 and all my images seem to get captured at 180 pixels /

inch.
Images aren't captured at any value of ppi, rather they are captured at a
specific number of horizontal pixels and vertical pixels. Somewhere your
camera has inserted 180 as the default. The pixels per inch value is only a
scale factor and has no importance.
Jim

 

[Steve]

Hi Jim, thanks for you input. OK, let's see if I got the gist of what you
just said.

So the 180 ppi value that I see when, for example I do "Image > Image
Information" in Paint Shop Pro, has been embedded in the meta data of the
image (by the camera firmware?), so that an application that opens the file,
can set the "rulers" or other "guides" in some meaningful way. Is this what
you are saying?

Steve

 

[John Inzer]

I'm not exactly sure where you are going
with this question but I'll try to offer some
ideas.

180 DPI is the Canon standard. Changing
the camera's compression settings or the
image size does not affect the DPI...this
would have to be accomplished with editing
software.

Your best bet is to set your camera for the
highest possible quality and if you require
smaller files for e-mail, etc...do it after the
files are safely downloaded onto your hard
drive. I suggest that copies of all original,
unedited image files should be saved on
removable media. It's good insurance...

Maybe the following article and some of
the links it contains will offer some insights:

DPI - Printer Resolution
http://tinyurl.com/wu5j

 

[Steve]

Hi John, thanks for the link to some very interesting & informative
articles.

I wasn't really "going" anywhere with the question. I'm very new to this
digital photographer / imaging stuff and I was simply trying to understand
the relationship between the myriad of often (for me anyway) confusing
acronyms.

My images have "EXIF Information" which states "X resolution 180.0 dpi" & "Y
resolution 180.0 dpi" and if I open the images in Paint Shop Pro the image
rulers are set to conform to the 180 dpi resolution. So this would be the
size of the printed image, if printed on a Canon printer. Is this what you
are saying when you state 180 dpi is the Canon standard.

Thanks for your patience, Steve

 

[John Inzer]

If you go to the following website,
http://www.steves-digicams.com/
you can view and download sample
images from many different brands
and models of digital cameras.

If you view the EXIF data for the various
samples...you'll discover that Sony images
for example are 72DPI, Canon is 180DPI,
and Nikon is even 300DPI. However...
the image resolution size for size is
the same. IOW...a 4MP Sony image, a
4MP Canon image and a 4MP Nikon
image are all basically the same...
2217x1704. These images will all print
equally well.

If you go to this page...
http://www.steves-digicams.com/2005_reviews/s2is_samples.html
you can download comparable shots
both from a "Canon S2 IS" and a "Sony H1"...
you will find that shot for shot ...they are
very similar even though the Canon DPI is
180 and the Sony DPI is 72.

Truth is, I guess I don't even understand
your question.

 

[Steve]

Hi John, well for someone who doesn't understand the question, you're doing
a pretty good job of answering it.

Truth is, maybe I wasn't sure exactly what I was asking. Unfortunately
that's a common bi-product of just "not knowing" but you've got to start
somewhere, right?

So it seems that the 72 / 180 / 300 DPI values are pretty much arbitrarily
set (by the camera manufacturer?) and don't have any impact on the "quality"
of the image. So, quality of image capture is all about resolution /
compression and quality of image printing is all about printer DPI
specification.

Thanks again for your help, Steve

 

[John Inzer]

Now you are getting it. Did you read the
message from Jim? I practically wrote a
book trying to explain what he said in a
couple of sentences.

In the case of the files you download from
your camera...the size is fixed regardless
of the DPI.

On the other hand...if you were scanning
an image. The DPI you choose...changes
the size of the file.