Flickr EXIF Search

Flickr EXIF Search, originally uploaded by blech.

Recently, I have begun to tag each of my photos with information about the camera and lens used to take the photo. It’s easy to add another tag to a batch when I’m uploading new photos. However, it’s a bit more time-consuming to go through my old photos on flickr and determine which photos were take with which lens.

Then I had a thought: the camera model used to take a photo is encoded in the photo’s EXIF data; so are the focal length, shutter speed, and aperture. The specific lens used is not included in the EXIF data, as far as I know. But using the information that is is there, it ought to be possible, I thought, to locate all the photos that were taken with a particular lens.

This led me to search for a way to locate photos on flickr based on their EXIF data. Amazingly, there's very little information out there about how to do this. I did find this one photo though, and in it one can clearly see two search parameters that don’t seem to be publicly documented by flickr:

• xfl — the maximum focal length; find photos with this focal length and shorter;

• xah — the minimum aperture (maximum f-number); find photos with this aperture and wider (this f-number and smaller).

Using these parameters, it's possible, for example, to perform the following search:
Find all of my photos tagged with climbing, with an aperture of f/2.7 or wider, and with a focal length of 50mm or shorter.

I have only one lens faster than f/2.8: my 50mm f/1.4 prime lens. So any photos returned by this search must have been taken using this lens.

Does anyone know if these and other EXIF-related search parameters are documented anywhere? I'd really like to learn more about how to perform searches using EXIF data.

Also, I would really like to know how to perform batch operations on the search results. Is there a way to add all of the results of a search to a batch in the flickr organizer? If not, there ought to be.