Yes but you’ll have to manually edit each caption so that is looks like this:
<a href=http://theurl.to/your/image.jpg class=fancybox >caption text</a>
(where you change http://theurl.to/your/image.jpg to the full size image URL in question)
As it currently stands this does not work. It links to the same image but it looses the text that would sit on top of the picture for some reason. Here is what my code looks like.
[caption id="attachment_33081" align="alignnone" width="150"]<linktoimage.jpg"><img class="size-thumbnail wp-image-33081" alt="Test" src="imagethumbnail.jpg" width="150" height="150" /></a><a class="fancybox" href="linktoimage.jpg">Caption</a>[/caption]
Also it seems when implementing it this way as opposed to through the wordpress gallery that the overlay text is severely limited in length. Any way to get around that?
Ah yes, the title is taken from either the alt attribute or the title attribute. When clicking the link in the caption, there is neither alt nor title… Change that link to something like <a class="fancybox" title="Test" href="linktoimage.jpg">Caption</a>
About the limit in length, I have no idea where that is coming from…
