Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Computing > Digital Photography > Another resolution question (sorry!)

Reply
Thread Tools

Another resolution question (sorry!)

 
 
Jeff Taylor
Guest
Posts: n/a
 
      08-24-2004
Well, I'm starting to get the hang of all this PPI, DPI, image size etc.
thanks mainly to some excellent posts to this group.
When I import images from my Fuji S7000 and open them in Photoshop, the
default resolution is 72 ppi (which I gather is correct for viewing on a
monitor).
Tonight I imported some images from the wife's new Nikon Coolpix 3200
and when I opened them in Photoshop, the default resolution is 300 ppi.

So my question is, what determines the default resolution of imported
images - do the camera manufacturers decide?
All images were imported using Windows explorer as opposed to the
software that came with each camera.

Thanks Folks,
--
Jeff Taylor
 
Reply With Quote
 
 
 
 
Jeremy Nixon
Guest
Posts: n/a
 
      08-24-2004
Jeff Taylor <(E-Mail Removed)> wrote:

> So my question is, what determines the default resolution of imported
> images - do the camera manufacturers decide?


Yes. The "ppi" on a file from the camera is entirely arbitrary and
totally meaningless.

--
Jeremy | http://www.velocityreviews.com/forums/(E-Mail Removed)
 
Reply With Quote
 
 
 
 
Jim
Guest
Posts: n/a
 
      08-24-2004

"Jeff Taylor" <(E-Mail Removed)> wrote in message
news:UotwVJACI5KBFw$(E-Mail Removed)...
> Tonight I imported some images from the wife's new Nikon Coolpix 3200
> and when I opened them in Photoshop, the default resolution is 300 ppi.
>
> So my question is, what determines the default resolution of imported
> images - do the camera manufacturers decide?

It certainly seems so. Of course, since all that matters is the pixel
count, all you need to do is resize the image to whatever display ppi you
choose. Just make sure that you tell the program not to interpolate.
Jim


 
Reply With Quote
 
Gisle Hannemyr
Guest
Posts: n/a
 
      08-24-2004
Jeff Taylor <(E-Mail Removed)> writes:
> Well, I'm starting to get the hang of all this PPI, DPI, image size
> etc. thanks mainly to some excellent posts to this group.
> When I import images from my Fuji S7000 and open them in Photoshop,
> the default resolution is 72 ppi (which I gather is correct for
> viewing on a monitor).


That depends on the monitor. Some are 72 ppi, some are 100 ppi
and some are 144 ppi, etc.

> Tonight I imported some images from the wife's new Nikon Coolpix
> 3200 and when I opened them in Photoshop, the default resolution
> is 300 ppi.
> So my question is, what determines the default resolution of
> imported images - do the camera manufacturers decide?


Yes. From a Canon G5 you would get 180 ppi, etc.

Please also note that the only use Photoshop make of this number is
to compute the "Document Size" which it display in the "Image Size"
dialog. It is not used for anything else (for instance - it is /not/
used by Photoshop to figure out what resolution to use for displaying
the image at the screen - and it is not used by the the printer to
figure out how big to print (there may be exceptions to this - but I
don't know of any printer driver that pay any attention to the
EXIF-embedded resolution)).

In other words: You may safely disregard this figure - but /if/ you
are not happy with whatever default your camera uses, you can change
it to whatever you like in the Image->Image Size dialog in Photoshop.
As long as you make sure that Resample Image is unticked, changing
this figure will not change your image in any other way.

> All images were imported using Windows explorer as opposed to the
> software that came with each camera.


I don't think that import route matters. The inital ppi is just
a meaningless figure embedded by the camera firmware in the EXIF,
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
================================================== ======================
«To live outside the law, you must be honest.» (Bob Dylan)
 
Reply With Quote
 
Jeff Taylor
Guest
Posts: n/a
 
      08-24-2004
In article <(E-Mail Removed)>, Gisle Hannemyr
<(E-Mail Removed)> writes

<snip> lots of useful info.

Many thanks Gisle, Jeremy & Jim.
Very helpful as usual - it all just gets clearer by the day
What a great group this is!

Best Wishes,
--
Jeff Taylor
 
Reply With Quote
 
Jim Townsend
Guest
Posts: n/a
 
      08-24-2004
Jeff Taylor wrote:

> Well, I'm starting to get the hang of all this PPI, DPI, image size etc.
> thanks mainly to some excellent posts to this group.
> When I import images from my Fuji S7000 and open them in Photoshop, the
> default resolution is 72 ppi (which I gather is correct for viewing on a
> monitor).
> Tonight I imported some images from the wife's new Nikon Coolpix 3200
> and when I opened them in Photoshop, the default resolution is 300 ppi.
>
> So my question is, what determines the default resolution of imported
> images - do the camera manufacturers decide?
> All images were imported using Windows explorer as opposed to the
> software that came with each camera.



The 'DPI' of an image is the 'Proposed print size'.

DPI has *nothing* to do with the quality of the image file
or quality of the pixels as they exists in memory.

As a matter of fact.. The DPI setting consists of a
couple of bytes at the beginning of the file. That's
all that gets changed when you change DPI.

The DPI in a file can be zero, but most cameras and image editing
programs will add a default value. Some add 72, current Canon cameras
add 180.. Others add 300.

Note that dots Per Inch *cannot* exist without inches because dots
per inch is nothing more than the desired print size (in inches)
divided by the number of pixels.

Setting a 1000 pixel wide image to print across 10 inches
of paper will result in 1000 / 10 = 100 dots being spread
across each of the 10 inches of paper. In other words, a
1000 pixel wide image printed at 10 inches has 100 DPI.

It's mathematically impossible for it to be anything else.

If you change the DPI of your 1000 pixel image to 500,
then the image will be 2 inches wide.. (1000 / 500 = 2)
Again.. A 1000 pixel wide image printed on 2 inches
of paper MUST be 500 DPI.

If you check your software you'll see that there are *always* two
things shown in the image 'size' window. These are: The DPI
*AND* the size of the image print in inches. (Remember.. you
can't have DPI without inches).

If you grab a calculator, you'll always see the DPI is *NOTHING*
more than the number of pixels divided by the *proposed* print
size in inches.

If you change the print size in inches, you'll see the DPI changes
accordingly. (DPI = Pixels / inches)

If you change the DPI, then the inches change.
(Inches = pixels * DPI)

Note there are ways to resample images when you resize. Resampling
adds or subtracts pixels from your image file. If you change the
image size, and resample, you're doing TWO separate things.

The resampling process can sometimes fool people.

Many people think changing a large image to 72 DPI will make it fit
nicely in their monitors.. This is absolutely wrong. The only
reason it fits is because IT WAS RESAMPLED.

Changing an image to 72 dpi to fit the monitor is about as useless
as changing an image to 600 DPI to match the printer

A 200x200 pixel image will look exactly the same on any monitor
at 10 dpi, 72,dpi 200 dpi or 1000 dpi...




 
Reply With Quote
 
Gene Palmiter
Guest
Posts: n/a
 
      08-25-2004
I still think my proposed explanation is best. The ppi (pixels per inch is
more meaningful than dots per inch) should be seen as an "IF' statement. If
printed to screen at 72 ppi its this size....if printed to inkjet at 200 ppi
its such a size....if printed offset at 300 ppi its such a size.


"Jeff Taylor" <(E-Mail Removed)> wrote in message
news:UotwVJACI5KBFw$(E-Mail Removed)...
> Well, I'm starting to get the hang of all this PPI, DPI, image size etc.
> thanks mainly to some excellent posts to this group.
> When I import images from my Fuji S7000 and open them in Photoshop, the
> default resolution is 72 ppi (which I gather is correct for viewing on a
> monitor).
> Tonight I imported some images from the wife's new Nikon Coolpix 3200
> and when I opened them in Photoshop, the default resolution is 300 ppi.
>
> So my question is, what determines the default resolution of imported
> images - do the camera manufacturers decide?
> All images were imported using Windows explorer as opposed to the
> software that came with each camera.
>
> Thanks Folks,
> --
> Jeff Taylor



 
Reply With Quote
 
Eugene O'Brien
Guest
Posts: n/a
 
      08-25-2004
The difference between DPI and PPI is fairly vague. I wouldn't say that
any one is particularly more useful than the other. It's just
terminology. Some people may be happy to call dots on paper pixels,
others prefer to say dots, either way it's pixel dimensions that really
matter as most other respondents to this thread have indicated.

> I still think my proposed explanation is best. The ppi (pixels per inch is
> more meaningful than dots per inch) should be seen as an "IF' statement. If
> printed to screen at 72 ppi its this size....if printed to inkjet at 200 ppi
> its such a size....if printed offset at 300 ppi its such a size.
>
>


 
Reply With Quote
 
Eugene O'Brien
Guest
Posts: n/a
 
      08-25-2004
Gisle Hannemyr wrote:

> Jeff Taylor <(E-Mail Removed)> writes:
>
>>Well, I'm starting to get the hang of all this PPI, DPI, image size
>>etc. thanks mainly to some excellent posts to this group.
>>When I import images from my Fuji S7000 and open them in Photoshop,
>>the default resolution is 72 ppi (which I gather is correct for
>>viewing on a monitor).

>
>
> That depends on the monitor. Some are 72 ppi, some are 100 ppi
> and some are 144 ppi, etc.
>
>


Trying to determine the ppi of a monitor is not a particularly useful
thing to do. It depends on viewable area which varies for all makes and
models of monitors, plus you can easily resize the display area with the
monitor adjustments, this will likely mean that if you actually got out
a ruller you'd find the PPI could be something 76.665 ppi.

It's best to just consider PPI fairly irrelevant for anything screen
based. It's much less confusing to always think about pixel dimensions
of images when working on screen.
 
Reply With Quote
 
JPS@no.komm
Guest
Posts: n/a
 
      08-27-2004
In message <0YMWc.12873$(E-Mail Removed) >,
"Jim" <(E-Mail Removed)> wrote:

>It certainly seems so. Of course, since all that matters is the pixel
>count, all you need to do is resize the image to whatever display ppi you
>choose. Just make sure that you tell the program not to interpolate.


There is usually no reason to set a PPI value for an image at all,
unless you want the file to automatically print at a certain size with
no user interaction. Just tell the program you are printing with what
size you want the image to be on paper, when you are printing it. If
the number of pixels would result in pixellation, then resample by 200%
or 300% before printing, after saving the file (if desired), and say no
to the changes when it is time to close the file, and you still have the
original.
--

<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
John P Sheehy <(E-Mail Removed)>
><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><

 
Reply With Quote
 
 
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
LCD TV resolution / DVD resolution ? slonkak DVD Video 0 11-13-2006 02:34 PM
How do you change the Modelsim Cursor Resolution (not simulation resolution) Andrew FPGA VHDL 0 09-26-2005 04:05 AM
Scanning resolution, printing resolution, and downsampling hassy_user Digital Photography 11 10-27-2004 07:18 PM
Resolution resolution Simon Digital Photography 4 02-27-2004 01:53 PM
ISO Resolution Chart and Printing Resolution Jack Yeazel Digital Photography 0 08-11-2003 11:19 PM



Advertisments