Camera resolutions

Richard49 · May 24, 2003

As we all know all (I hope) digital cameras produce images with a resoultion of 72ppi (or is it dpi?).

So am I to believe that (in my case) using Photoshop I can increase the resolution of an image to 300dpi to make it suitable for printing?

I can understand about reducing the resolution of an image but not increasing it.

If that's the case then surely you could increase the resolution of an image to any desired dpi no matter how rediculous it might be?

Maybe there's somewhere on the Internet that explains this in easy to understand terminology?

Lin Evans · May 24, 2003

Richard49 said:
As we all know all (I hope) digital cameras produce images with a
resoultion of 72ppi (or is it dpi?).

So am I to believe that (in my case) using Photoshop I can increase
the resolution of an image to 300dpi to make it suitable for
printing?

I can understand about reducing the resolution of an image but not
increasing it.

If that's the case then surely you could increase the resolution of
an image to any desired dpi no matter how rediculous it might be?

Maybe there's somewhere on the Internet that explains this in easy
to understand terminology?

We really don't all know that, because digital cameras don't produce images with a fixed pixel density at all. They produce an array consisting of a matrix of "X" pixels wide by "Y" pixels high.

For example, the typical 2 megapixel sensor samples at 1600 x 1200 sites which produce a 1600x1200 pixel matrix. The "density" depends entirely on the "display" resolution or "print" resolution. You take those 1600x1200 pixels and display them at a fixed numer of pixels per inch on a monitor and this equals an image size of so many pixels across by so many pixels down. This, in turn, equals so many "inches or centimeters" wide by so many tall at the particular display resolution. When you look at the image in PhotoShop, it tells you that the currently displayed image would be so many inches wide by so many inches tall at 72 pixels per inch. If you tell PhotoShop to make the image 300 pixel per inch in density, then the "size" changes accordingly. You are simply pushing those pixels into a smaller space. So the smaller the print size, the higher the "print resolution" becomes. If there are not sufficient pixels to print at the desired resolution such as 300 dpi at a desired size print, then a software process called "resampling" is used to "interpolate" and add pixels. It does this by examining adjacent pixel values (these are simply numbers at this point) and creating intermediate values. This is done throughout the image and the result is an image which has the proper number of pixels for the print size and print density desired.

Lin
--
http://208.56.82.71

RAL131504 · May 24, 2003

Lin Evans said:
Richard49 said:

As we all know all (I hope) digital cameras produce images with a
resoultion of 72ppi (or is it dpi?).

So am I to believe that (in my case) using Photoshop I can increase
the resolution of an image to 300dpi to make it suitable for
printing?

I can understand about reducing the resolution of an image but not
increasing it.

If that's the case then surely you could increase the resolution of
an image to any desired dpi no matter how rediculous it might be?

Maybe there's somewhere on the Internet that explains this in easy
to understand terminology?

Click to expand...

We really don't all know that, because digital cameras don't
produce images with a fixed pixel density at all. They produce an
array consisting of a matrix of "X" pixels wide by "Y" pixels high.

For example, the typical 2 megapixel sensor samples at 1600 x 1200
sites which produce a 1600x1200 pixel matrix. The "density" depends
entirely on the "display" resolution or "print" resolution. You
take those 1600x1200 pixels and display them at a fixed numer of
pixels per inch on a monitor and this equals an image size of so
many pixels across by so many pixels down. This, in turn, equals so
many "inches or centimeters" wide by so many tall at the particular
display resolution. When you look at the image in PhotoShop, it
tells you that the currently displayed image would be so many
inches wide by so many inches tall at 72 pixels per inch. If you
tell PhotoShop to make the image 300 pixel per inch in density,
then the "size" changes accordingly. You are simply pushing those
pixels into a smaller space. So the smaller the print size, the
higher the "print resolution" becomes. If there are not sufficient
pixels to print at the desired resolution such as 300 dpi at a
desired size print, then a software process called "resampling" is
used to "interpolate" and add pixels. It does this by examining
adjacent pixel values (these are simply numbers at this point) and
creating intermediate values. This is done throughout the image and
the result is an image which has the proper number of pixels for
the print size and print density desired.

Lin
--
http://208.56.82.71

This might help, or might confuse more, but anyway. If you use the 2mp camera example above you typically have an image of 1600x1200 pixels. If you print this image on a 10 inch wide piece of paper you will have 160 ppi (pixels per inch) - if you printed this same image on a 5 inch wide piece of paper you would have 320 ppi. You could print either of these images on a 300 dpi (dot per inch printer). Dots per inch are primarily associated with printers and printing, pixels are the imaging sensors used in the camera.

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Camera resolutions

Richard49

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Lin Evans

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RAL131504

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