dpi stands for ';dots per inch'; -- ppi stands for ';pixels per inch';. They essentially mean the same thing. dpi comes from printing, ppi comes from imaging. If you set ppi in photoshop, you are creating the dpi equivalent.300 DPI means how many PPI?
Right on. But Smithsonian magazine doesn't understand the distinction.
Are you submitting electronically? If so, you will never be dealing with dpi. Chances are, they made a technical error is requesting ';dpi'; output in a jpg that will be sent as an e-mail attachment.
If they want a print, you can set the ppi to 300 and use the highest quality settings on your printer and it will come out the way they want.
You might want to read this: http://www.rideau-info.com/photos/mythdp
Especially see the section DPI vs PPI (although you may find the whole article helpful).
But to highlight the main point of the article... DPI (or PPI -- in this context they mean the same thing) was used by some older image editing software to determine the size of the print. Although advanced software such as Photoshop, GIMP etc still allow this feature, it is no longer required for setting the print size. And it is certainly not used by browsers for determining the on screen display size.
It can be useful to know the very simple maths involved so you can have an idea of the print quality when printing an image at any specific size.. but it is not required to know this. And it is pretty much meaningless to pay attention to or to change the DPI of an image for 2 reasons.. firstly it has nothing to do with the resolution of an image (that is determined by pixel dimensions - commonly referred to as it's megapixel count). Secondly, as I already mentioned it is no longer required for setting the print size.. since image editing software have better and easier ways to do this (often found in the 'print preview' dialog).
But if you must set the DPI in order to keep the competition people happy, be sure to turn off 'resampling' prior to making the change.. otherwise the pixel dimensions will be altered -- which could negatively affect the image's quality.
in image editor, check size for print, pixels, and resolution,
view print options as is, for dots per inches, if image is already adjusted to 300 卤, then it is ok,
if image resolution setting is 72/92/144 ppi or other, with the image size in inches the same XbyY size, change resolution ppi, but keep image size ppi, but test print output setting for dpi, if ok, save copy of original
in print options view print resolution,