Depth of Field Scale
I've been taking photographs with digital cameras for over 12 years and have never got around to learning how to read a depth if field scale!
The depth of field scale can be useful for setting the focus to maximize the front to back sharpness or hyperfocal distance.
There are other methods for calculating Hyperfocal distance using charts or mobile phone Apps and I have included some comparison test shots and 100% crops to illustrate my experiences.
This is a fairly un-scientific but real world test of these two methods
Hyperfocal Distance - Using Depth of Field Scale
Set your lens to an aperture - say, f/16 (NOTE: Too small an aperture can result in diffraction effects that result in progressively less sharp images at small apertures so generally aim to for f8 or f11 depending on lens quality)
Since your lens is set at f/16, find the "16" markings on the depth-of-field scale on the lens. Position the infinity symbol below the "16" mark. This brings infinity just within the depth-of-field at f/16
Now, you are no longer focusing directly on infinity. Depending on the lens, you are now focusing on a distance of around seven to ten feet away and everything from around half that distance to infinity should render acceptably sharp.
Hyperfocal Distance - Mobile App Calculations
I used the DoF Plus App on iPhone to calculate the Hyperfocal Distance for the Fuji 16mm lens at f16 on a Fuji X-T2.
The App gave me a focusing distance of 81.6cm which I measured out and focused to using the Lens Auto Focus.
81.6cm seems pretty close and gives a good option if you have foreground objects that are very close (as close as 40.8cm) to the camera sensor.
Hyperfocal distance calculations take into account the camera model, focal length of lens and aperture as well as a sharpness factor known as the circle of confusion (CoC) the CoC is based on the premise that only objects directly on the focal plane are in critical focus and the CoC informs you that objects nearer or further away are acceptablty sharp. I understand that the value is based on whether objects in a certain sizes print appear sharp over a given viewing distance.
Like most things in Photography there is no right answer and there are always compromises to be made. In the case of the precise Hyperfocal Distance gained from the Mobile App what you gain in near object focus you lose in overall front to back sharpness.
I have gotten by over the years focusing about a third of the way into the scene but I think I will give the Depth of Field Scale method a try in the wild. It is not always the case that everything in the scene needs to be sharp front to back but when it does it's useful to have options to try.