Re: resolution question

msb3 wrote:
> 
> When I open my photographs it always shows them as 72 pixels / inch

That is just a number your camera puts in the resolution field of
the image header. It has *nothing at all* to do with the quality
of your photo.

> which I
> really thought would be higher b/c I take them at the highest resolution

You are confusing two different concepts. First there is optical
resolution, which has to do with the quality of your lens and the
number of sensor elements in your camera. It measures your camera's
ability to distinguishably render objects that are close together
in the scene you are picturing. Once you have purchased your
camera you really have very little control over this, beyond
setting the camera to use the maximum available number of sensor
elements, focusing properly and avoiding camera shake. The second
use of the word resolution (and the one you are dealing with
here) is as a conversion factor. It converts the pixels of your
image to inches of printed image on paper. Pixels are the
natural information-carrying elements of a digital image. Based
on how the human eye works, to get a high quality print to view
at arm's length you need about 200 pixels per inch of width or
height of the print on paper. Anything above 300 pixels per inch
is a waste since you won't be able to see any extra detail.
a high quality print your

> and
> it shows the size at 2560 x 1920 which is a huge file

No, it's not a huge file. It is only about 5 megapixels. Cameras
with 12 megapixels are available and 8- or 10-meggpixel cameras
are quite common. The more sensor elements you have in your
camera when you capture the scene the more pixels you get and
the more detail you can capture (at least potentially).

> I know but I like to
> crop a lot so I always just take at the highest resolution.

Forget technical terms like "resolution" unless you can go to
the trouble to learn exactly what they mean and an understand
instinctively what are the implications of different values in
different situations. Instead, set your camera to give you
the largest images in pixel units of which the camera is
capable. This will give you the highest quality image and
permit the most cropping.

> Is this the
> actual pixels per inch of my photos or a default that PSP uses?

Resolution in pixels per inch is simply a conversion factor used
when you print your images (assuming you don't override the
setting in some way in the Print command). The rule is:
    Inches = Pixels / Resolution_in_pixels_per_inch
The size in inches *only* applies to printing your images. It
has no effect whatsoever on the appearance of the image on your
monitor, since that depends only on the number of pixels in the
image. You can prove this to yourself very easily. Do Image >
Resize. Uncheck Resample Using. Then type in a number for the
Resolution between 1 and 32767 and press OK. The image will
look just the same as before. However, when you do Image > Image
Information you will see the changed resolution number and you
will see that, for a given size in pixels, the inch size will
be larger the smaller the resolution you said. When you go to
print your image set the Resolution to 200 ppi in the way I
described. Image Information will then show you the largest
inch size you can print the image and still have it look good.

The answer to your question "Is this the actual pixels per inch
of my photos or a default that PSP uses?" is in two parts. When
the image contains a resolution value in the file PSP will use
it. Only when there is no resolution value does PSP use a default
resolution. The lack of a resolution value is fairly rare,
examples being GIF files (which don't contain any resolution
field) or images pasted into PSP (which might not contain a
resolution value stored in the Windows clipboard). When PSP does
use a default value to replace a missing resolution it is the one
found in File > Preferences > General Program Preferences > Units
under Default Resolution. Unless you changed this setting it
will be the one PSP uses when it is first installed, namely
200 pixels per inch. The reason for this value I have already
explained. I think, however, that you are getting JPEG files
from your camera and that your camera is writing the number 72
in the resolution field of the JPEG file. It is a stupid number
to write but it is not uncommon to find this done (even though
it is something dating back to the history of the first Apple
computers).

When I open my photographs it always shows them as 72 pixels / inch which I 
really thought would be higher b/c I take them at the highest resolution and 
it shows the size at 2560 x 1920 which is a huge file I know but I like to 
crop a lot so I always just take at the highest resolution.  Is this the 
actual pixels per inch of my photos or a default that PSP uses?

Thanks! 

msb3 wrote:
> 
> thank you so much for taking so much time to give me such a detailed
answer
> with so much information.... it was awesome the way you broke things down
> for me.

No problem.

> I do believe I have a higher setting on my camera than the one it
> was on and it also takes in different formats like .tiff but I am confused
> enough as it is....hehe

Being confused is something you can remedy.

thank you so much for taking so much time to give me such a detailed answer 
with so much information.... it was awesome the way you broke things down 
for me.  I do believe I have a higher setting on my camera than the one it 
was on and it also takes in different formats like .tiff but I am confused 
enough as it is....hehe 

Tim Morrison wrote:
> 
> Spandex Rutabaga wrote:
> 
> >The reason for this value I have already
> > explained. I think, however, that you are getting JPEG files
> > from your camera and that your camera is writing the number 72
> > in the resolution field of the JPEG file. It is a stupid number
> > to write but it is not uncommon to find this done (even though
> > it is something dating back to the history of the first Apple
> > computers).
> 
> It's pretty stupid, but it's also the default in the EXIF specification. A
> lot of cameras seem to just write that instead of something more useful.

The great thing about standards is that there is one for every
occasion :)