One of the confusing aspects of digital imaging is resizing and/or cropping an image.

DPI Vs Image Pixel Dimension

Many digital camera images today are bigger and contain more information than is required to print your std photographic print (say 10x15cm).

This is the result of cameras capturing pixel, not "dots".

DPI is a printing term derived from the capability of the printer.

Mega Pixels (in digital camera speak) refers to the resolution of the camera and is calculated by the millions (mega) of pixels it can capture.

A 7.0MP camera will capture (at highest resolution) 3000x4500 pixels.

This is the equivalent of :

100cm x 150cm print if printed @ 72dpi

50cm x 75cm print if printed @ 150dpi

25cm x 38cm print if printed @ 300dpi

if when cropping an image in an editing program like photoshop or Corel Draw, keep in mind the printer your intend to print the image on and its DPI capability,

NB inkjets refer to resolutions like 1440 dpi, etc. The true resolution of and injet printer is this advertised number divided by the number of colour cartridges it contains. ie the std inkjet has a colour gamut of CMYK and therefor hase 4 separate cartridges. Divide 1,440 by 4 to determine the resolution required to match the printer (ie 360 dpi)

IE A high DPI number does not always translate into sharper text or more detail being visible.

In reality not many people can pick the difference between an image printed @ 250dpi Vs one printed @ 300dpi, or 400dpi.