Firstly what do I mean by image optimisation?

I'm not talking here about taking a beautiful photo and then enhancing it by adjusting the exposure, contrast, vibrance, saturation etc, (although that is something I am very much interested in). What I am talking here about what to do once you have that image in order for it to be viewed on-line.

Most photos after they have been processed in Lightroom or an equivalent photo editing application are output in JPEG format with a .jpg extension and they may be several MB in size. If they are destined to be printed then this is the file that you need but it is not the file you need for a website. 

A website image needs to be fast loading and for this to happen it needs to be correctly sized and optimised so that it is the smallest size in KB that it can be, consistent with it still being a good quality image. In particular your page's Home page which is most probably your main landing page, needs to be built with this in mind. The speed of loading that page is fairly critical to the success of your website, so slowing it down by loading a huge photograph, no matter how good looking it is, is not a good strategy. 

This should also apply to other pages that a viewer may land on after doing a search. These are commonly called landing pages. Other pages may not be so critical such as a gallery page, or a contact page.