Focus Stacking - A Primer

Sometimes when you need to have a wider range of focus your camera equipment can fail you.  This is often the case for subjects in the macrophotography world where even tiny apertures are incapable of resolving a full field of acceptable sharpness. 

Using the tilt and shift functions of a large format camera can solve this dilemma quite easily. However, most photographers do not have the luxury of owning such a wonderful piece of technology as that. So, what are the options? 

Focus Stacking. This is the process of shooting multiples of the same image with varying points of focus, then stacking them together into Photoshop to create one image. 

Here's how it's done (it's quite simple):

1. Use a tripod. This cannot be done handheld! 

2. Compose your image and select an aperture. I like to use whichever aperture my lens performs it's best at. For this shot, I used my Hasselblad Makro 120mm. I find this lens is at it's best at f11. (Generally speaking, the 'middle' aperture is it's best for sharpness and corner-to-corner color rendition.) 

3. I find it's easier to start at the top and work your way down. Focus on the upper most part of your image and take a shot. Focus a little lower down your image and take another. Continue this until you've reached the bottom. It's better to err on the side of having too many shots, than not enough, or else there will be blurry bands in your image.  The number of images you take depends on how shallow your depth of field originally is.  

For extreme macro work, there's a machine out there that will do this more precisely for you. But, since this is a relatively easy shot to begin with, I can do this by hand with no problems. 

4. Take your images and open them up in Photoshop. Drag each image into one of the files, creating layers. 

5. Select all the layers and then go to Edit --> Auto-Align Layers. In the resulting menu, select Auto and then 'Ok'.  This is a crucial step as changing focus also changes your angle of view slightly. 

6. With all the layers aligned and still selected, go back to Edit --> Auto-Blend Layers.  Then select 'Stack Images' and 'OK'. 

7. Bingo! Here's your image perfectly (hopefully) sharp from top to bottom. There will be some blurry bands at the very top and bottom since the lens changes your angle of view as you refocus. But, that can be fixed in post-production. 

Here is the final image after I tweaked with some dodging and burning. 

Mamiya 645 DF with Hasselblad Makro-Plannar 120 #15 tube - f11 @125th 50iso