Hi - I'm noticing some weird watermarking behaviour on a client's site. They've set up a default watermark, which is supposed to be added to every image on upload. However if you check out this album:

http://retrospectivecycles.com/bianchi-corse-52cm/

Some of the thumbnails link to the standard image URL e.g. /cache/bianchi-corse-52cm/img_7665_820.jpg, but others link to e.g. /zp-core/i.php?a=bianchi-corse-52cm&i=img_7667.jpg&s=820&cw=0&ch=0&q=85&wmk=!&check=67d4e6d0a641a3b8a85f85664a11d7a4d9dbf31b - which don't load in the lightbox.

Is this to do with caching or watermarks in fact?

Thanks

The first link is to an already cached image, the second to the image processor that caches an image.

As you hopefully know ZP does this on the fly and on request by default (the watermarks are addedn then and not on upload!). Unless you setup your theme to use the cache_manager plugin to precache.
http://www.zenphoto.org/news/caching

The lightbox (colorbox) of course does not load non image content by default. You can configure it to treat everything as a photo: http://www.jacklmoore.com/colorbox/ (see option "photo" way down).

I've figured it out now, thanks. I upgraded my lightbox script (Fancybox), and in the new version I needed to set a 'type: image' option to force the script to treat the php link as an image.