When I shot this Periwinkle in my garden, I had to take my camera very close. The depth of field was low, as you can see from the image. A breeze was blowing and the flower was moving with the wind. The challenge was to get a sharp picture all over the flower.
I used the nine focal points of my Canon EOS 550D to shoot several images with the focus on different parts of the Periwinkle, from the farthest to nearest. I then used Photoshop to stitch all the photos together.
The shutter speed was at 1/160 sec to avoid motion blur.
To do a Photomerge, open all the images in Photoshop. Then select File>Automate>Photomerge. In the Photomerge dialog box, click on Add Open Files. Then click OK.