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Pixels and dpi - what does it mean?
Every digital image is made up from Pixels. A pixel is the smallest picture element containing information that makes up all digital images. Understanding at least the basics on what a pixel is will help you better understand exactly what size you need to make your photo for a particular purpose - but more on that later.
A pixel is the building block of a digital image and typically a photo contains pixels that are made up from 24-bit pixels. Basically, this means that each pixel can be made up from 8 bits of red, blue and green colour information. The 8 bits from each primary colour is actually 256 individual tones or hues, which can be combined into a pixel that can be any 1 of around 16.7 Million different colours.
When it comes to viewing a photo on your computer screen you are also viewing pixels. Your computer screen is made up of it's own pixels and a typical screen size is 1024 x 768 PIXELS (786432) or just under 0.8 Megapixels. A computer screen can usually display either 16 bit or 24 bit colour and as we just mentioned 24 bit is ~16.7M colours. Computer screens generally display at 96dpi (dots per inch) - and DPI/PPI is covered in a seperate article. So when it comes to showing photos on a computer screen we don't need a huge image.
We don't always want to display photos on a computer screen and often want to print them out. Pixels are just as important when it comes to printing. A printed digital photo typically has 300 PPI and needs more pixels to produce a quality photographic print than displaying the same photo on a computer. We discuss this in greater detail in our article on preparing your photos for printing.
For more in-depth technical details read more about pixels in the Wikipedia
When you need to resize more than 1 photo at a time we use and recommend BatchPhoto. This software is capable of not only resizing a batch of photos it can also do several other tasks to your batch of photos as well such as renaming.