Proceeding to the Camera-lens Settings and Focus Stacking panes rises some questions:
Example: f=85mm, f/8, I leave the pupil factor at 1, because I am too lazy to determine it; I want the max DOF, so I set Focus Distance to the hyperfocal distance=55.53 m.
In landscape, the whole frame is the "object". The tool shows width=23.48m, height=15.66m. Which significance has this? Does it have any influence on the subsequent calculations?
The object/subject dimensions are the scene 'frame' dimensions in the focus plane. This is used for determining if a subject that is focused on, will fit in the frame. It's mostly used to fit e.g. a building facade with known dimensions, or a person of known height, or a car or a truck of known length, a painting of known dimensions, etc., within the frame. You get the idea what it can be used for. A landscape is not typically measured that way. It is directly related to the sensor size and magnification factor, and the latter is directly related to the focal length and focus distance. So in that sense it's related to all other parameters and vice versa.
Then, I copy the settings to Focus Stacking and assume that I want DOF from 5 m to infinity.
What is the Goal Distance Range? (In the example, it is given as 9.999e+ - I have a vague feeling this means "infinity".)
The goal distance range is the depth you want the focus stack to have, the goal you want to achieve by stacking, in case you have a specific range in mind (e.g. an object or subject that needs to be sharp from a given distance to another distance). Since you've focused on the hyperfocal distance, a single slice will already span the distance from half the hyperfocal distance to infinity.
- What is the Search: Front-Rear-Aperture? Regardless which of the radio buttons I click, nothing seems to change.
When you change the total range or depth of the zone you want to have in focus, you need to instruct the program where to look for an expansion of the range. Upon changing the total range, you can have it expand that range by searching for a new front distance (and keeping the rear unchanged), or for a new rear distance (and keeping the front unchanged), or for a new aperture that allows to span the range from front to rear (which may fail when the range is larger than can be achieved by the smallest aperture you can select, and will be heavily diffracted).
3.5 is called the MAX number of images, 6 in the example. These 6 slices are without any overlap. So shouldn't 3.5 be named MINIMUM number of images? In real life, you want overlap, Helicon recommends it, so you will need more slices. Or ...?
The number of slices needed is the automatic result of focal length, aperture, COC, and Total range to cover. You can limit that number of images by entering a lower maximum. Increasing has no use, because the front to rear distance will already be covered by fewer slices. Setting a lower maximum can be useful for limiting the number of slices to a specific number, e.g. the length of a focus rail in macro where each image is shot with the same magnification factor and thus slice depth. Especially when selecting a relatively close front distance, that can result in an impractically huge number of slices which will take a long time to calculate, it can be useful to then set a limit. Other than that, it is not that often used for input, but rather for reporting the total number of slices.
There is no real need to overlap the slice boundaries because you've already selected a resolution on sensor that is 'perfectly' sharp (according to COC limitations) in the end result, based on the prior input parameters. In fact the sharpness between the DOF range boundaries will still increase towards the plane of optimal focus in between those boundaries (unless limited by sensel pitch), but you won't be able to resolve that in the output by eye. There will be no visible gaps in sharpness between the slices, which should indeed be avoided, hence the recommendation by HeliconSoft.