Does anyone have code to show a different caption per photo? I would like to link to the original image page, where EXIF etc. is available. Or are there different methods to accomplish this?

What exactly do you want to do? There is a description for each image. It will be different therefore for each image. If you have an IPTC description it is captured as the image description.

I am sorry if I am not completely clear.
I want to add this to the slimbox album view. Regular website users love the way slimbox shows the images, but photographers want to see EXIF and other data. That's why I want to offer a link to the original (image.php) page, where all data is. I do not succeed in linking to that in the slimbox view, perhaps I need to fiddle with Javascript?

To be more exact, an example on my site:
<http://www.lalunerouge.net/kunst/ester2/> works perfectly (even on an iPhone!).
Some photographer friends want to view <http://www.lalunerouge.net/kunst/ester2/IMG_1726.jpg.php> for more information, or have a button to show the EXIF data. I can not just add a link in the slimbox caption, because it has to be different for each image.

I guess you will need to modify the slimbox script then (or use another variant maybe), especially as using image.php or a lightbox script are different concepts actually.

I guess so too, I have seen some javascripts to change the caption of an image but they seem quite complex...
Do all slimbox (or lightbox or ...) users just go without EXIF data?

I am using not slimbix, but floatbox and with this you can do things like that you can show the exif data below the caption of the picture, if they are opend in the lightbox like you can see here if you open a picture:

http://www.rdmag.de/photo/wacken-2008/

If this is what you are searching for just ask and I will show you the code.

Best

martin