Bit of a query (dearie)

JayD

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Probably a basic one. When I look at the exif information from an image, my 400d has 72dpi. My Panasonic compact has 180dpi, does this mean the compact is taking better photos or what? I'm confused!
 
It does not mean anything :)
Your camera only captures pixels. The saved file has no dpi - there are no inches in a saved file so you cannot have dots per inch!
It is only relevant when you are printing when you can choose to print very large 10 dpi (each pixel 1/10 inch across) or very small 500dpi (each pixel 1/500 inch across) silly examples I know but it may help you get the idea.
A number has to be present otherwise the maths have nothing to work on, different cameras insert different values, when you load the files into a program and select resizing then you may see other figures depending on the program you are using. I have seen some programs use 72 some 240 and others 300 and I expect that there are more.
Although most programs still use dpi a few are now using ppi as nowadays we tend to talk about a picture having so many pixels rather than so many dots. DPI can then be used solely to say how many dots an IJP will spray out, they normally spray more than 1 dot of ink per pixel so you can print a picture at 300 ppi at 1200 dpi (So you are printing 300 pixels every inch and 16 dots of ink per pixel)
 
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Cheers, thanks for that. I'm not confuzzled anymore. , :D
 
Great explanation Kev. The program I use for cropping my photos, Jasc Paint Shop Pro 7, uses a standard 72dpi and my photos on the screen work out at 72" x 48" at full size. If I'm printing I usually set to 300 - 400dpi depending on what print size I want. The Panasonic software just displays at 180dpi and other programs use different settings. You can alter the standard settings of your program if you wish but a 72 x 48 inch size is great to check how sharp the photo is at full size.
 
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