Photographers who wanted to try high-dynamic-range imaging in pervious versions of Photoshop had a lot of learning to do first. And eve then, results usually weren't comparable to those you could get from a good stand-alone HD creation program. In CS4, you have to merge images to create a 32-bit HDR file, then convert it down to 16- or 8-bit for real adjustments. The new version of this tool called HDR Pro, works differently. You can still work in 32-bit mode and convert your image down later. But, you can also do that right in the Merge to HDR Pro dialogue. Set the mode to 16- or 8-bit, then use the adjustment sliders to get a file you like.