I have used PhotoAcute Studio for jobs involving focus stacking, or extended DOF (depth of field). It did a better job for me than other programs out there, even though it wasn't perfect. I still have to be prepared to do plenty of hand-masking. Like all programs, including PS, it can't read your mind. So I was very interested to hear that Photoshop CS4 now included the ability to stack images with different DOF. So I availed myself of the 30-day demo and took it for a spin.

My first test is a side-by side comparison of a focus stack using 4 exposures. I'll be doing a tutorial on using PhotoAcute before long, but here's the process in Photoshop CS4:

1. Select your series of developed images (in my case, they're tiffs) in Adobe Bridge CS4. Tools > Photoshop > Load Files into Photoshop layers. Hooray! I've wanted this feature for a long time.

2. Once it's all in PS: Edit > Auto Align Layers. If you leave this step out of a focus stacking, you'll be sorry.

3. Now you can Edit > Auto Blend Layers, and select the "Stacking" button. 

4. You'll be returned with nicely masked layers (love it!), optimized for the focused areas of your exposures. Optimized, but not perfectly. Again, if you're a fusspot, you'll want to be prepared for some hand-masking work.

How all this compares with PhotoAcute

As you can see from the side-by-side snapshot, the Photoshop stack on the left has better detail and less distortion, but some edges need work. With the masks ready to go in the layered PS file, this is much easier.

The PhotoAcute shot is on the right, and you can see the distortion, but better blending. Using PhotoAcute, I've had some images skew to the point of objects being pushed out of the canvas entirely, and had to modify our photography to allow for it. I will do some further tests before posting a verdict.