@ebiggs1 wrote:"... depending on depth of field, a range of distances will be in acceptable focus."
This called the hyperfocal distance. It is the closest distance at which a lens can be focused while keeping objects at infinity acceptably sharp. When the lens is focused at this distance, all objects at distances from half of the hyperfocal distance out to infinity will be acceptably sharp.
A "range of distance" for accpetable focus is just "depth of field". "Hyperfocal distance" is a slightly different concept.
For any given lens focal length and aperture value, there is a focus distance which will maximize the depth of field. That magic value which maximizes depth of field (just for that specific focal length and aperture value) is the "hyperfocal distance". Any other value may achieve a very broad depth of field, though not necessarily the most broad depth of field possible.
Every lens focal length, focused distance, and aperture value combination has a "depth of field" -- but it's not necessarily the "hyperfocal distance".
A new photographer might think that to maximize depth of field they could just focus the lens to infinity and use a high aperture value, like this:
The above camera lens is set to f/22 (which should generate a broad depth of field) and it is focused to "infinity". If you look at the blue boxed area that I've annotated, this shows the range of distances at which your subjects should be in acceptable focus. It looks like everything from about 12' to "infinity" will be in focus.
The problem with this is that it wastes some depth of field. Because the lens is "also" focusing a range of distances which are "beyond infinity" and since nothing can be "beyond infinity" we really just lose the benefit of that range.
So to achieve a true "hyperfocal" distance, we can change our focus distance like this:
In this example, since I'm using f/22, I move the "infinity" mark on the focus ring to the "f/22" mark on the back-side of the depth of field. Everything between the two f/22 marks on the depth of field scale should be in acceptable focus. Notice my blue box is much bigger and now everything from about 6' to infinity is in acceptable focus. This change has gained about 6' in the near-foreground area which will now also be in acceptable focus.
This concept (the second shot) is the magic "hyperfocal distance" for this 50mm lens at f/22. There is no other focus distance which can achieve a broader depth of field than this one.
DoF marks are still found on many prime lenses, but not so much on zoom lenses... because the DoF depends on the focal length. Once upon a time, most zoom lenses used a "push/pull" to slide the lens longer or shorter. Today most lenses have a zoom ring that rotates (no longer a push/pull -- though there are still some push/pull lenses around.) Push/pull lenses had a sweeping set of arcs to draw the DoF marks -- but it's not possible to do this with zooms that have a rotating ring (which is most modern zooms.)
With zoom lenses today, best to look up the depth of field on a table. If you have a smartphone there are a number of apps you can use. You can also make printed tables.
To learn about DoF in the beginning, it might require that you consult the tables (or apps) often, but I find that with enough photography you eventually get a feel for how much depth of field you get in a situation. As you compose favorites types of subjects using favorite lenses and similar compositions and distances, you find the settings that work -- and arrive at the point where you can take a shot, dialing in the correct settings without even really thinking too much about it (because you've done so much shooting.)
