D2 - File Formats, resolution etc.

      File Types

      There are many different file format types and they all affect size and quality of images in different ways. File formats are how the information is put together so that it can be saved as a file type.  The main file formats for images are:
      1.       JPEG – these files would usually be used for digital/photographic images
2.       PNG – these files would usually be used for web images/graphics
3.       GIF – for text, graphs and icons etc.
4.       PSD (Photoshop Data File - can only be used in Photoshop)
·         PSD files allow you to save your Photoshop project so that you can go back and edit it at a later time. It keeps all the layers, layer styles and objects, but if you save a Photoshop image as anything other file you wouldn't be able to do this.
  
     Compression Techniques

      File Compression
      File compression is when a file which takes up a large amount of data is reduced/compressed. Compression of an image will reduce the quality, as you can see above I have changed my files to different JPEGS. The first image is a digital high quality JPEG that has the best and very clear quality and resolution. The problem with this is that it takes up 6.59M, whereas the other images range from 487.9k to 97.6k but the image quality differs, this depends on whether the JPEG has a high or low quality format. Compression is used mainly for images that are going to be put up on the internet because it means that they won’t take as long to load.

       Image Resolution

      Resolution is the measurement of the quality in an image and it is usually measured in pixels or dots, the measurement terms are PPI (Pixels per inch) and DPI (Dots per inch). PPI is for graphics on screen and computer resolutions and DPI is when referring to printing. 

     The higher the resolution in an image, the better quality it will but it will take up more memory when stored. Web graphics are usually 72 PPI and digital photographs can be around 300 PPI. 

    Vector files don't distort as they are made up of pixels and are made from mathematical equations, this means that they keep their quality.
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      Colour Depth

      Colour depth is the number of bits used to represent colours in an image or photograph, and the higher the numbers of bit of colour the better the image. Colour depth can affect the file sizes too as if the colour depth is high the file size will increase but the quality will remain good. GIFs have a limited colour palette so having a high colour depth would seriously increase the size on a GIF file.