Lee Hird Fine Art Photography : Understanding dof Part 3:Focus Stacking

So we know about hyperfocal distance. But what happens when we are close to an image? Here is an image of an old speaker. I wanted to get the top face in focus. My settings were ISO 400 f32 and 1/6 sec exposure with my 90mm lens.

Image taken at f32

No editing was done with this image. As you can see, the image has good depth of field but the back of the speaker is a bit soft. I cannot dial in more aperture and I don't really want to have the decking totally sharp. So what is a solution? Yeap - focus stacking.

Photographers, both landscape and macro, often use focus stacking to enhance the sharpness. The reasons for using this method include:
1. When we stop the aperture all the way down (f32 etc), dof increases but lenses suffer from diffraction causing a loss of sharpness.
2. Poor light but good dof is still needed.
3. Artistic reasons to use the aperture wide open (say f1.2) and play with focus and blur with other elements in a scene.

If you are going to focus stack, then in the field remember:
1. Use tripod to keep the scene fixed.
2. Set your exposure
3. Take several shots from near to far where only the point of focus is changing.

All we are really doing is creating a smaller dof by using say f4 or f8 and overlapping these windows of sharpness to cover the scene in question. Then in post processing (say in Photoshop) we blend them together to create 1 sharp image.

Going back to the speaker, I used f8 ISO 400 and 1/80 and took a series of images where the front, the middle and the rear of the speaker were respectively in focus. After blending the images, here is the result.

The grill is sharp all the way to the back.

Here is how I used Photoshop (CS6).
1. I shoot in "raw" so I opened each image and saved as a tiff. I used meaningful names like near.tiff, mid1.tiff, mid2.tiff, far.tiff
2. To open all of the images so that each layer in photoshop is one of these images simply: File -> scripts -> load files into stack then find and select your images.
3. Once all of the images are loaded, you will see the image names as a new layer. (giving a decent name to the image makes sense now :-)) highlight each layer. Now we need to align then. Edit -> auto-align layers. At this point make sure all geometric corrections are deselected.
4. Once aligned we get Photoshop to blend them to create one sharp image.... Edit -> auto-blend layers choose the "stack images" option and the "seamless tones and colors" option.
5. Sit and wait.

Don't forget to save your image :-)