resizing question

I'm just getting into the digital process, and was wondering if someone requests a specific size in inches of a photograph that is to be burned to CD for them, is there a general resolution (600x800) etc. that equals say 5x7 when printed from a CD file? Or do I not get it at all? Or maybe I should say what would be a good low resolution size that would print a decent 5x7 photo if MB/KB doesn't matter.

Thanks,
Cynthia

Unless they provided a different print resolution to use, you should be safe going with 300dpi. In this case, the physical size will be 1500x2100 pixels (5x300 by 7x300).

If you're using Photoshop, you can set the size in inches and 300dpi as the resolution. This information will be embedded into the file when you save it.

Guy

Thanks Guy, that explains a lot...now I get it... "dpi x dimension"...I never put the two together...and I kept hearing that dpi didn't matter. When doesn't dpi matter?

dpi doesn't matter until you want to print or otherwise use an image to fit into a certain size. That's because you don't have the "inches" part of the equation until you know what size you want to print.

The confusing thing to so many, is that often people that should know better (printers or contest managers, etc.) ask for images to be a certain dpi without telling you what the inches are. This really means nothing. To ask for an image that is 300dpi with no other info is useless. Just as to ask for a digital image file that is 5"x7" without defining a resolution (dpi) is useless. If someone that should know better asks for a specific file for a specific use, they should either give you the size AND dpi or just the pixel dimensions (xpixels * xpixels).

Sorry about the rant but it's one of my pet peeves. I have seen many contests that ask for a 300dpi image.

Hope this helps.

Thanks Mike...that clears up a few questions I've had. I've noticed that some contests now ask for file sizes instead (usually to small to be much good when enlarged). I've always wondered what I wasn't understanding, and now realize the info really was missing....so thanks for the explanation. The request I've had is not specific, and they are leaving it up to the photographer, but they want it to be a photo file of low resolution, but decent enough that it looks good at 5x7 if they have to print it for clients. So I'll follow Guy's rule of 300dpi. But here's another question, how is low resolution defined? "Low" I'm guessing just means not a huge file so you reduce the dimensions. I've noticed when I resize the dpi doesn't seem to change the file size if I change it to something lower than what it is. For example, I have some scanned slides at 400dpi and resizing changes the file size but reducing it to 72dpi doesn't make it a smaller file than at 400dpi...what am I not getting, is it because the same amount of information is still there but the 72dpi would make a lesser quality print in the end but I don't see it on a computer screen?

Mike said the magic words with respect to dpi: "dpi doesn't matter until you want to print or otherwise use an image to fit into a certain size."

DPI is used only for 'print' resolution. It means, basically, 'Put x number of ink dots per inch on my page'. So, changing dpi will have no effect on image file size. Your computer screen display is pixels per inch and is set by the video card. That's why a 1000 dpi 5x7" image looks identical to a 72 dpi 5x7" image on your screen.

-P

Thanks all for clarifying my questions so well.

For max print quality you want to do 300 dpi at the target print size so you would want to do 1500x2100 for a 5x7.