Bob, you apparently don't understand the resolution number either. The
72dpi (or any dpi number for that matter) is not something that's
physical until it's tied to a print size. There may be a tag in the
EXIF image data that says 72dpi but that's all it is... a tag. You can
change it to anything you want but it has absolutely no physical effect
on the image. It's an advisory value to a display or print system
(should such system choose to honor it) that says print or display this
thing at whatever physical dimension you get by dividing the horizontal
and vertical pixel counts by the resolution value.
Your camera does not shoot images at 72dpi. It shoots images at
whatever the native image size is... in pixels. Assuming you've chosen
the full size image it shoots images that are 2592 x 1944 pixels.
Whether the resolution tag says 72dpi or 7200 dpi doesn't change the
image one bit... it's still 2592 x 1944.
That said, one needs to be careful in PhotoShop with that dpi number.
If you change it in the image size dialog *and if* the "resample image"
option is checked it will have an effect on your image. If you enter
that dialog with an image that is 2592 wide with a resolution value of
72dpi the print size of the image will be shown as 2592/72dpi = 36"
wide. If you then change the resolution to 144dpi without changing the
print size and also have the "resample image" option checked you will
increase the size of the image to 5184 pixels. It will double the
number of pixel columns by interpolation.
Just remember that the image itself is nothing but *dimensionless*
pixels. Dimensions only come about when we decide at what density those
pixels will be diplayed or printed. Photoshop will happily add or
delete pixels if you allow it to in order to meet your request for a
certain size image at a given resolution.
Chuck Norcutt
Bob Whitmire wrote:
> Someone said the images were 72 dpi, but quite large. My Olympus
> C-5060 digicam shoots 72 dpi images that are, like, 20x30. Scott
> Kelby in one of his books teaches a neat trick to covert a huge 72
> dpi file to a very useful and much smaller 300 dpi file that then can
> be worked in such a way as to provide an excellent fine-art print. My
> best-selling image was shot with the C-5060, at 72 dpi, and treated
> according to Kelby. Just the other day I printed a quite acceptable
> true 16x20 out of it.
>
> --Bob Whitmire
> www.bobwhitmire.com
>
>
>
> On May 17, 2007, at 5:11 AM, khen lim wrote:
>
>> 72dpi , always.
>
>
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