Question on image resolution in Photoshop

[mr_marks]

<p>I am in the midst of preparing some artwork for publication. I saved an image in TIF format at 1200 dpi resolution. When I checked the resolution of the image by right clicking on it and selecting "properties", the horizontal and vertical resolution is at 1200 dpi. When I open the same image in photoshop and select image->image size, the resolution shown is only 300 ppi. Why is there is a difference? Thanks for any inputs in advance!</p>

[q.g._de_bakker]

What matters is how many pixels there are in your image. That will not have changed.<br>The dpi setting is information used by printers, and is something you can change at will without changing the image itself (as long as you uncheck any "resample" or "resize" options).

[Wouter Willemse]

<p>To eloborate a bit on what Q.G. wrote: the dpi / ppi settings are only used to "define" how many pixels will be used every inch. For most normal print work, this is usually 300.<br /> The actual resolution of a file is something else: it is how many pixels it has in total; for example, a digital camera may create a file that measures 4000 pixels on the long side and 3000 on the short (giving a total of 12 million pixels, more commonly called 12 megapixels). In photoshop, you should primarily worry about the quantity of pixels (*not* the dpi or ppi setting), to retain as much as possible throughout working on the file.</p>

<p>The one thing you may need to look out for is whether you have enough resolution for the intended print size. Taking the above example figures, using a 300 dpi printing quality with the 4000*3000 pixel image gives a 13" x 10" print. Print larger, and quality will drop. Smaller - no issue.<br /> Check with the publisher how you need to deliver the file. Maybe there is no need at all you worry about dpi and ppi, and the printer will take care of that for you - which will make life a lot easier.</p>

[digitaldog]

<p>To understand resolution: http://www.digitaldog.net/files/Resolution.pdf<br>

Yes it's really old! Nothing has changed however. I really DO need to update it as a modern video and cover Lightroom. In the meantime, you'll see that the resolution '<em>tag</em>' is rather meaningless and the way to work is by understanding the number of total pixels you have over hight and width. </p>

[q.g._de_bakker]

And to elaborate on <i>"The actual resolution of a file is something else: it is how many pixels it has in total."</i>: It's rather unfortunate that the word "resolution" is used for that, because that is "size", not resolution.

[Wouter Willemse]

<p>True, and sloppy on my part to not distinguish; it is where the whole confusion starts, isn't it?</p>

[vilk_inc]

<blockquote>

<p>And to elaborate on <em>"The actual resolution of a file is something else: it is how many pixels it has in total."</em>: It's rather unfortunate that the word "resolution" is used for that, because that is "size", not resolution.</p>

</blockquote>

<p>sounds like "quantity" of image to me, not "size," <em>n'est-ce pas</em>? :)</p>

[q.g._de_bakker]

Only, Vilk, if the size of, say, a book expressed in cm is also called "quantity". Interesting question though: is a larger image also more image? Does size matter anyway? ;-)<br>But, if another word must be found, how about "dimension"?