How do I change the DPI of an image?

I need to change my photo from 72 to 300 dpi with photoshop. Do I simply change the resolution from 72 to 300, or is there something else I have to do?How do I change the DPI of an image?
Wow. Such variety.



In Photoshop, you have two important sections in the Image Size dialog: Pixel Dimensions and Document Size.



Lets pretend you have an image that is 1000 pixels x 500 pixels at 100dpi. Your numbers will look like this:



Width: 1000

Height: 500



Width: 10 in

Height: 5 in

Resolution: 100



If you just change the resolution in the Document Size, you will see that the number of the pixels in your image automatically changes at the top. If you change the resolution to 300, the numbers will look like this:





Width: 3000

Height: 1500



Width: 10 in

Height: 5 in

Resolution: 300



You're telling it to add in a bunch of pixels and the image will end up icky. Whenever you change your resolution, you should reset this number if you don't want the image to be degraded. If you go back and retype the top number, you will then see the size change:





Width: 1000

Height: 500



Width: 3.333 in

Height: 1.667 in

Resolution: 300



You'll get a crisp picture because you haven't added or subtracted any pixels from your image. Of course, you can allow Photoshop to add or subtract pixels from your image, but if you were to go from 72 to 300 dpi without taking into account the number of pixels, you would add in nearly 4 times the pixels. This is one of several reasons taking images from the web doesn't work.



In short, when you change the DPI in Photoshop (or any program), you need to make sure that you are not distorting your image by adding and subtracting extra pixels. Check the top box, too.How do I change the DPI of an image?
Pay no attention to that answer about 300 dpi, etc. Here's the deal:



DPI, refers to ';DOTS'; per inch -which is to say, the resolution of the PRINTER -how many times it lays down a dot of color or skips a space (for ';white';) in an inch of space.



But you asked about dpi for the PICTURE; which is to say the source image, itself. What we're really talking about here is pixels -the number of dots that make up the image file. You could very well change the image resolution to soemthing other than the OUTPUT resolution.



The answer, I think, is pretty much what you say - change the resolution to whatever you want. Which will simply mean that the image will be made of more (or less) dots than before. But it will still be the same picture. It won't get any sharper because you take more dots (pixels) to make the same picture.



HOWEVER, it matters if you change the physical dimensions of the output. The bigger you make it, the fuzzier it will look when viewed at the same distance as the smaller version.



The other issue is editing the picture; you can be more precise with higher resolution because not as many pixels are selected when you use the lasso, do a clone or apply other effects. A nose comprised of 10,000 pixels can be more exactly modified than one of just 100 -right?



The other consideration is physical size of the image -as an image (not as output). If changing resolution means also changing the physical size that will be output, it matters. Obviously, a 3 inch square that is 300 pixels per inch will be more precise than one which is 6 inches square, because the same data (picture info) will simply suck up more pixels to get the same image.



Clear?



I didn't think so, either.
Mystik is right



To assure you have enough data saved on your cameras memory card, always shoot at the cameras highest image quality and largest image size. Then you will have much more data to work with when preparing an image to be printed (on either a inkjet or at a lab)
I don't use any version of Photoshop, I use Paint Shop Pro X2 and if I want to change the so called DPI I can do this by using the re-size (or re-sample) option and where it says 72 DPI (or what ever it is) I can set it to any # I want, including 300 (or 600 or 800..).



I can also keep the image ANY size I want as well and not make it larger, smaller or anything. It can remain the same. I just increased the DPI from one # to another.. and nothing else.



http://www.rideau-info.com/photos/index. - and read The Myth of DPI..



Bob - Tucson
Image/adjust/size change resolution to 300 and lock aspect ratio. The image will become smaller because the information is at 72dpi. Quality will diminish because it was a jpeg too.