How do you change the dpi in photos?

I read some questions pertaining to this subject, but I'm still unsure.



I need a photo of myself that is 300 dpi. Now, I've had photos taken of me from my digital camera, but they come out as only 250 dpi.



There's a program on my computer called ArcSoft PhotoStudio (I don't have Photoshop) where I can upload a photo and change the dpi. I've done this to the 250 dpi photo and made it 300 dpi, but the photo, at least to my untrained eye, looks identical to the old one.



Should I be able to see any changes?



Is there a way that I can take photos that are uploaded as 300 dpi (my camera is a Kodak EasyShare C330)?How do you change the dpi in photos?
I am assuming you need a photo that is 300dpi at 100% of the size.



If your camera takes a 250 dpi photo and the photo is 10'; x 10'; and you only need the photo to be 5'; x 5'; you can change the dpi to 300 in photoshop and make the photo smaller and you should get the quality that you desire.



You can't keep the photo the same size. Simply changing the dpi in a photoshop will not give you a better quality photo.



Garbage in garbage out.How do you change the dpi in photos?
You couldn't see any changes. There is two reasons.

First your monitor is 72 dpi. The onlydifference will be in printing big sizes.

And do not forget 1inch x x 1inch 300 dpi photographs printable size is equal to 10 inch x 10 inch 30dpi photograph.

With out this proportional change you will add more pixels to your photograph if you add more dpi (dor per inch) or you lost some pixels if you reduce your dpi.