Filter controls with keyword search

We've tested a number of search interfaces and in general we've found that people often neglect refinement options. It could be that people are conditioned to the web search experience (particularly Google) and therefore are less inclined to take refinement steps as part of entering their search.

The search function at iStockphoto encourages visitors to refine by displaying the controls dynamically when the cursor is in the keyword search field:

Both the placement (under the search field) and the dynamic behavior (which catches the eye) helps bring these options to the user's attention.

Compare this treatment with that found on the Corbis site (click image to see full-sized):

Here the refinement options appear after the search field and button. Since the user's attention will initially be on the search field and button, the refinement options seem less discoverable in this position.