Optimizing images is very important. A website with many images can not be ranked properly because images and photographs are not correctly used thus grows the website response time (one of the key ranking criteria used by search engines).
The first basic element, that should be kept in mind, when we want to optimize images and photos is that you need to convert files of pictures and photos in smaller files that can help to have faster loading time of the site. This usually works by using images and photos lower resolution. Computer monitors operate on RGB (Red-Green-Blue) color mode and display images with relatively low resolution (usually 72-75dpi) unlike printers which use CMYK (Cyan-Magenda-Yellow-Black) color mode and the images must have higher resolution (at 300dpi).
In order to help you understand the difference, I will give you an example for an image sized 1000X700pixels. An image of this size with high resolution for printing purposes (300dpi) will give us an image file size of 5 MB while the same image with analysis of 72dpi gives a file of 80KB, and if you select to save the image for the WEB, then for the same picture will have a file of just 15-20KB.
Tip: Be aware, that photos or CMYK type pictures (basic four-color printer) can not be diplayed on the computer screen due to the difference in color mode they use.
The second essential element when we use pictures and images on our website, is to save them using a name representative for the image and to avoid names like image1, photo2 etc.
Finally, for every photograph or image that we use, we should be include a short and representative description. The advantages of this practice are numerous. We help disabled people to understand the content of the image. We make it easier to search engines to check the relevance of the image with the contents of our website, and we help them to integrate our images and photos into image search program. As a result, our website will be better ranked by search engines.