Trying a new technique here. I’m trying stacking several photographs (in this case 4), each shot at f8 and each shot with a different point of focus so that the level of in-focus and sharp elements throughout the scene is greater than if I used just one frame.
If I were to shoot one shot with a small aperture of say, f18, depending on certain factors, it can still be difficult to get everything in the scene sharp and in focus. There is a scientific and reliable formula to try to achieve such sharpness if desired, but I usually just focus about 1/3 of the way “through” the scene, and in most cases this works pretty well for me. So, why stack several frames with different focus points?
Every lens is different, but every lens has what is called a sweet spot for sharpness, and one thing is for sure… that sweet spot for my 17-40mm lens is not at f18 or higher. This means that if I choose to shoot at f18, any benefits I get from an extended depth of field are usually negated by degradation of the image from diffraction, especially if I am positioned very close to parts of the image.
So, without getting into a topic that is too complicated for me to understand – never mind explain – I shot this scene at f8 to see if I could get a cleaner, sharper image. In this case though, one shot at f8 would not provide sufficient depth of field and sharpness throughout the image for my liking, so I made four images of the same scene each shot at f8, but I changed the point of focus each time. Here’s a pretty simple explanation from the DPS web site of how you might use this technique on a macro shot.
FYI… in these four frames I focused on the very near foreground rocks, the bottom edge of the tide pool, the top edge of the big slab of rock, and then the furthest headland. I then stacked those four photographs in the computer and used the Photoshop auto-align capability to “line everything up” correctly. A few blending shenanigans later, and I had created one image with the result posted above.
On most smaller, web-sized photographs you can’t really tell if everything is sharp front to back, so here’s one that is a little bit bigger than I usually post so you can hopefully see at least some of the impact this process had on overall sharpness. Normally both the very front rocks and the very far trees would be less than sharp, even if I had shot with a small aperture, but in this version they are both noticeably sharper. Like most things, this technique “works” on some scenes and not others… and then there’s creative interpretation.
Bottom line… is the full-sized original of this image cleaner and sharper when shot and processed this way? Yes, actually it is. Am I willing to invest the time and effort needed to shoot and process every image this way? Hmmm… maybe, maybe not.
Disclaimer: every digital image needs to include some degree of sharpening in the post-processing workflow, and this one was treated as I treat all of my other photographs posted to the Interweb.