unit 30 d2

Unit 30 D2

The purpose of any file format is to store your data and reduce the amount of space taken up on your storage device. Some formats do this at the cost of image quality, JPG in particular reduces the image quality when reducing file size. The are called LOSSY file formats. Other file formats such as PSD and TIFF do not alter the image quality however do not offer as much saving in file space. Original JPEG has 4.4 MB file size, TIFF has 10.4 MB, flat PSD has 30.7 MB, and TIFF has 37.3 MB storage. These sizes are when there has been no alterations to the image quality. The one difference is the container in which the file formats are stored within.

GIFs are good at compressing images and are suite for simple drawings, wheres as JPEGs have millions of colours, they are optimized for more complex images but do not compress them well. The more you compress a file the smaller the size gets, however the image quality is also reduced along with the file size. GIFs will always retain the original image quality because they are not LOSSY file formats. LOSSY file formats being compressed suits them for the environment in which they are used in however ruins the image quality. Decreasing the image quality can be worth it if the file format needs to be small for the environment in which it is used in.

Compressed files are significantly smaller than their uncompressed counterparts, and they fall into two general categories: lossy and lossless. Lossless compression ensures that all image information is preserved, even if the file size is a bit larger as a result. It never discards information about the original image. You want the output to be in high resolution for this, it is used when compressing files of importance such as school work, bank information etc. Lossy compression, by contrast can create file sizes that are significantly smaller, however achieves this by selectively discarding image data. Lossy compression creates smaller files by discarding (losing) some information about the original image. It removes details and color changes it deems too small for the human eye to differentiate. Lossy compression results in pixels and resolution lost after compression, this is so the file can be used more efficiently and at a lower file size.The compressed image is therefore no longer identical to the original. Visible differences between the compressed image and the original are called compression artifacts.

This print screen shows that changing the file type from the original decreases the file size however decreases the image quality. This can be seen more clearly when looking at the red roses on the image, they become more unclear when using the GIF and PNG file formats. The JPEG file is good however not as good as the original. The image of worst quality is always smallest in file size. The file type has a direct impact on the image quality and file size.

This print screen shows the effect for compression techniques on the image quality and file size. The file size a decreased massively as a result of compression techniques, e.g the image with 0% image quality (bottom right) is much less clear than the image with a quality of 100% (top right). However the image with 0% quality has a file size of only 1M whereas the highest quality image has a file size of nearly 10M. The difference in resolution isn't very noticeable at first sight, however a closer look shows the images decreasing in resolution when compressed more.

This print screen shows the effect that colour depth has on image quality and file size. The right top picture has 256 colours and is therefore the clearest GIF file out of all 3. The bottom right image has 16 colours and therefore becomes very unclear and it is hard to distinguish between different parts of the image. However the most unclear image with 16 colours has a file size of only 1.9M, whereas the most clear image with 2566 colours has a file size of just under 6M. A user would have to decide what is more important, image quality or file size. The more colours used in an image increases the file size of the image because there is therefore more information to be stored in regards to the amount of colours. The less colours used, the lower the resolution. The objects in the image become a lot less clear and it becomes a lot harder to make out what they are.