When I share content from my site it posts an image to Facebook as it should. I have noticed that the image is small, roughly 100x100 at best. Yet on other people's posts of content from other sites the content is much larger. (320x320 roughly.) I do not know why the images from my site are reduced to such a small size. The images on my site are much larger than the thumbnails.
I use AddThis to share my photos. Is this playing a part or am I missing some code on my site? Any help with this is greatly appreciated and any clarification I can offer I will.
Update
I have added OG Tags as Nick recommended in an answer below, the image is still small, here is the code I used:
<meta property="og:title" content="My Title" />
<meta property="og:type" content="article" />
<meta property="og:url" content="URL Path" />
<meta property="og:image" content="Image File Path" />
<meta property="og:image:type" content="image/jpeg" />
<meta property="og:image:width" content="620" />
<meta property="og:image:height" content="541" />
Any ideas how to increase the size?
It might would help to understand why Facebook shows some images at one size and others and another size.