This is an HDR photograph edited using the techniques described in this guide. This photo was a challenge to edit because of the moving cars - you can't combine three pictures worth of moving objects and have everything come out looking good. Here's what the cars looked like immediately after I ran Photomatix to combine the three images:
So how do you deal with it?
Edit and Open Your Files
First, take your "0" exposure and reedit it as a single RAW. Part 4 talks all about how to do that.
Next, open your HDR file that has the problems in Photoshop. Then open your newly edited single RAW HDR file in a separate window in Photoshop. Here's what you'll see:
Match the Exposures
Working with your single RAW file, use a combination of curves, brightness adjustments, and exposure adjustments to get the problem area to match as best as you can. It doesn't matter if it looks "good" or not, just that it looks as close as possible to the image with the problems.
Select the Problem Area
Select the cars. Use a combination of quick mask mode and the quick selection tool to select, and refine the edge so it blends nicely against the background.
Copy and paste
Hit CTRL+C to copy your selection. Move back to the HDR image with the problems and hit CTRL+SHIFT+V to paste your selection into place.
Duplicate your new layer several times
At this point you're well on your way to getting the job done, but if you stop here you're still going to have some issues. Here's what the cars look like at this point:
To fix this, duplicate your new layer several times until the cars look good.
Merge your duplicated layers
Select all your layers except the background layer, right click, and hit "Merge Layers". Here's what you'll see:
Double check the exposures on each layer
You can now easily compare the exposures by clicking the layer visibility eye. Edit your cars layer further if there are still some big differences. It's important to match the exposures as best as you can.
Smooth the edges
Select the boundary of your new layer and refine the edge. Make the transition as smooth as possible while taking care to avoid selecting the problem area:
Hit OK and delete this selection.
Merge the visible layers
Merge the visible layers, edit your photo as you normally would, and voila! You have an HDR image with realistic looking moving objects!