I have this function call that displays an entire img tag with the correct url for that post.. the thumbnail img...

```
?php the_post_thumbnail('blog-page'); ?>

```

What I need is just the source address for that img. 

How can I get that source dynamically?

---

Here is a little more explanation of what it is exaclty that I'm doing...

This is the code that displays the thumbnail for a page in my wordpress:

```
<div class="entry-thumbnail">
<a rel="lightbox" href="<?php the_permalink(); ?>"><?php the_post_thumbnail('blog-page'); ?></a>
</div> 

```

I need that a tag's href to use the img's source instead of linking to the blog post it's self to get lightbox to work properly.