Area focus and depth of field scale: taking the Leica M7 manual as an example
Explain that depth of field is affected by focus distance, focal length and aperture, and use the 50mm lens example given in the Leica M7 manual to demonstrate the depth of field scale; fixed street photography distances across lenses and formats are not provided.
Depth of field changes with three conditions
The Leica M7 manual states that depth of field is related to the focus setting, lens focal length and aperture; closing the aperture (larger f-number) will increase the depth of field, and opening the aperture will decrease the depth of field. Depth of field is a visible clear range around the best focus plane. It does not mean that every detail within the range reaches the best sharpness on the focal plane. 〔G-ZF-01〕
Read the lens depth of field scale
According to the Leica M7 manual, the focus ring displays the set distance and, together with the depth of field scale on the fixed ring, displays the clear range at that distance. The specific reading depends on the scale of the lens itself. The scale of one lens should not be regarded as a universal value for all lenses. 〔G-ZF-02〕
50mm example in manual
The manual uses the Leica SUMMILUX-M 50mm f/1.4 as an example: when focusing at 5 meters, f/4 corresponds to a depth of field of about 4–8 meters; maintaining the same focusing distance and closing to f/11, the example range expands to about 3–20 meters. These are only the lens and sample conditions in this manual; actual image clarity is also affected by viewing conditions, focus errors and shooting conditions, and is not a guarantee of "full clarity from 1.5 meters to infinity". 〔G-ZF-03〕
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