Year 12, Unit 30, Task 8b, D2

In this report I will be describing and evaluating the impact that file format, compression techniques, image resolution and colour depth have on file size and image quality.

The purpose of any file format is to store data and to reduce the amount of space the file takes up on your hard drive, however some formats do this at a cost of quality. For example, JPG reduces file size by lowering quality (LOSSY formats). Other formats, such as PSD, don't alter quality however they do not offer as much savings in terms of file size.

In Photoshop, the files you save an image under is either PSD or PPD. This is because Photoshop allows you to change and edit specific layers however, the image file size is quite large which means you have to Adobe Photoshop to open them or another type of Adobe software.

GIF; graphic interchange format, is a type of bitmap format used for animations often on presentation and websites. It has a range of colours of around 256 which is an advantage as the file size stays small however it is hard reproducing the images.

JPEG, which is most commonly used format, is used a lot when taking pictures and downloading images, from the internet etc. There is a disadvantage with this format as the image quality is not very good especially when stretching the image as it can become pixelated or when zooming into the image as it is fit for a smaller file size.

There are two different ways in which files can be compressed and these compression techniques are LOSSY and LOSSLESS and each of these methods affects images. When compressing the image through LOSSY, the image loses some of the image data and results in pixels. This is so the file can be used more efficiently and at a lower file size. The amount of data loss is often adjustable. The high compression rate the smaller the output file but the image quality will be of a poorer standard.

LOSSLESS is the second compression technique and this is when you compress the image and expect it to be the same as before. Therefore you want the output high-resolution as this is used when compressing high-quality files for example school work. There are different ways of compressing the image to your standard however this effects the file size and can increase or decrease to your liking.

Image resolution can depend on the camera used or what the intended use of the image is. The amount of pixels that make up an image is its resolution therefore the more pixels used, the more quality and detail. A large file often indicates that the file has better resolution therefore a smaller file indicates lower resolution. Therefore the higher the number of pixels used in an image then the more space it will need to be stored on and camera or phone etc and for this a large memory stick will be needed.

The maximum amount of bits used in an image or hard drive is its colour depth. Depending on the amount of bits results in the different bits per pixel (BPP). Bits are worked out 2 to the power of 8, 16 or 24. If multiplied you get whats called a 'true colour'. With a large amount of bits, the colour and shading will be endless giving an infinite number of colours and of high-resolution. Therefore the file size of higher bits will be bigger as there are more colours per pixel. Colour depth is an important factor when coming to high quality image as the depth of the colour directly affects the file size with the better quality affecting larger file sizes, however will consist of much more detail.

Overall, file format have the better resolution than others. I have came to this judgement as although the file size of the image will be affected there are techniques which can decrease the file size with a compromise of the image quality. Also, colour depth is always essential when producing high quality images but the more colours you have the higher the file size will be.