You'll notice the names of your lenses/films used/cameras and so forth at the bottom of your entries near your name(which I've also made a category/subgroup), which means if you click on any of these at the bottom, they will appear as a subgroup.
If you click on Pinkham & Smith, all the Pinkham & Smith shots will appear as a group, and you won't have to fish around the complete site to find them, if you click on Pinkham & Smith Semi-Achromatic Doublet, all the SA Doublet images will appear together. If you click on your name, which is also a category/subgroup, all the images shot by you will appear as a group.
You can also do this when you originally post your images by going to the right of the 'entry date' box, and and clicking the 'browse' button inside the 'categories' box at the extreme right. A pop-list of categories will appear.
Hopefully this will increase the flexibility of this site.