I hope this can help someone. It is basic, but there are always beginners like me into the stacking process. I illustrated one of the things I consider when stacking or attempting to gather as much Depth of Field (DOF) in my shots.
Here we go: I hope this makes sense.
The following illustrations attempt to show how the camera film plane (SP)(sensor plane in digital) records the image when it focuses on a given subject. The yellow line through the back of the camera is where the SP is located. If you look at the bracket below the spider and flower, you will notice a series of red dotted lines that run parallel to the yellow sensor plane on the camera. When you focus on a subject, whether it be the spider or parts of the flower, there will only be one specific spot that will have the sharpest spot of focus. The space in front, and in back of, where you choose to focus will not be as sharp.
How do we get the image sharper throughout?
Notice there are red dotted lines running through the image of the flower and spider. When I stack the images, I am shooting a series of shots at numerous focus locations. (IMPORTANT) When you shoot a series, shoot them in order from front to back, or reverse. Do not mix the shots back and forth as the software for compiling the stacked final has more difficulty handling the mixed data.
The second illustration shows how you can increase the area in focus in each shot, and it also illustrates how tilting the SP to be more parallel to the subject surface can reduce the number of exposures required to capture the whole subject.
You will notice in the second illustration, the number of red slice lines are more than I need for the same subject in the first illustration.
Tilting the camera or the subject will enable you to secure captures with fewer attempts, and if you have a subject that will only let you get on shot before it moves, this is how you can increase the sharp field of view in a single capture.
I have been using this technique for over 35 years, and I am pleased with the results I get. I hope this was helpful to some of you as I see many people struggle with this concept when they begin in close-up and macro work.
Here is the summary: 1. Observe the subject and visualize where the flattest plane of focus would capture the most amount of detail.
2. Work in front to behind that single spot for your captures. Capture sequentially in one direction.
3. Don't change f stops within a series of shots.
4. Take more shots in the series as you subject angle becomes less parallel.
Remember, good equipment helps, but knowing what to do with it and how to handle the subject is essential in achieving higher end results. Good luck.