First, lets look at the merged image i.e. the outcome:
The whole robber fly is in focus, from head to tail...except the legs...
Now lets look at the two pre-merging images that contributed to the merged images above:
the left portion. Note that the right portion of this image is not very in focus.
the right portion
The merged images. Notice there's area with empty canvasses on the top left and bottom right. I could have just cropped these out but i chose to add canvas by using the clone tool because i wanted more breathing room for my robber fly.
Photoshop must have an intelligent algorithm to select the joint area!
I definitely couldn't have achieved the same DOF with a single shot. However, I only did this because the robber fly was to big to fit into the frame at the MP-E65's minimum magnification of 1:1 on the crop sensor of the 40D.
So give it a try. File - Automate - Photomerge, then browse and select the images you want merged. The rest is automatic!
Learn other photoshop tricks here:
1. Photomerging 6 shots into one
2. Manual focus stack for more DOF in CS3
3. Using clone tool to enhance image
All images shot with a Canon 40D, Canon MPE65 1X-5X macro lens and Canon MT24EX Twin Flash with DIY Diffuser.