Whenever you search Google images, the results are shown in small size and you need to open it from the website and then show full size image. This task can be time consuming if you are searching for lots of images. Google Image Help is a Firefox Add-on which helps you perform Google image results quickly by allowing view of the full size images directly. This add-on also supports for Bing and Yahoo as well.
Once you have installed the Add-on, next time you do an image search in Google, Bing or Yahoo, right click on any image result and you can see an option to open the image in full size. There is also option to open all images in full size.
This saves a lot of time if you like a considerable number of images on the current page and want to download them in their full size.