Focus Stacking

OK, I learnt a couple of new photography / Photoshop tricks yesterday with a tutorial from Gavin Hoey on Focus Stacking. This is about taking multiple shots of the same image to create an image with mega depth of field (stuff in focus at both short and long distances from the camera). The multiple images are taken progressively focussing from the nearest foreground item to the most distant.

Here's a link to Gavin's tutorial - Focus Stacking Tutorial.


I tested the technique out in my back garden and was very impressed so I thought that I ought to take something that would do justice to the technique, so I took a short drive to our local church in Rayne and this is what I got.

Quite a difficult shot to compose as the camera was about 2 inches off the ground. In truth I would have preferred a position about a foot or so to the right so that the metal grave marker in the foreground was silhouetted against the sky rather than trees but that wasn't feasible as there was a hedge there.

The technique works! The metal grave marker is about 18 inches from the lens and appears in focus as well as the distant church. The only downside is that, as the technique merges several images together, you can end up with edge artefacts which aren't too visible in this small image but at full size becomes visible (see the LH edge of the church, particularly at the top).

I'm wondering if the issue of edge artefacts is inherent to the technique as when you examine the images at different focus points you can see the images have slightly different coverage (closer focus images have wider coverage). This gives Photoshop some work to do when the images get merged and blended so is this potentially where the artefacts get generated?

Kit? EOS 5D MkII, EF 24-105 mm f4.0 L.

Exposure? 1/20 sec at f / 22, Focal length, 24 mm.