There is nothing new about this hyperfocal distance technique. Sir William de Wivelesley Abney¹ mentioned about the hyperfocal distance formula in his book in 1881. This focusing concept continued to develop until 1951, when Rudolf Kingslake² used the simplest formula to specify the concept. Hyperfocal distance is mostly known as a distance beyond which all objects can be brought into an “acceptable” focus³.
Hyperfocal distance is often use with normal and wide angle lenses since their focal distances are relatively shorter than telephoto lenses. For landscape photographers, this concept is the most useful technique to get everything in focus. For photojournalists and street photographers, this is the key to attain candid shots and quick focus. With the DSLR age, the depth of field scales have disappeared from the autofocus lenses and most of us seem to have forgotten or have never learned to use this hyperfocal distance technique. Some argue that it is unnecessary since autofocus lenses can perform faster and more precise focus. Some give up because they get confused with formulae, numbers and technical terms like Circle of Confusion⁴.
The concept can be confusing if we get too technical; otherwise, the formula is simple and easy to understand. Before we jump into the formulae, I’d like to clarify that hyperfocal distance and depth of field are not the same thing.
While Depth of field can be defined as the range of object distances within which objects are imaged with acceptable sharpness, hyperfocal distance is the focusing distance such that the far distance of acceptable focus is at infinity. Hyperfocal distance can also be 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.
Since hyperfocal distance has two definitions, there are more than one formula will be discussed in the next paragraphs. For the first definition, the formula is,
Hyperfocal distance formula 1
- H = hyperfocal distance
- f = focal length
- N = f/ stop
- c = circle of confusion limit
Below is the formula for the second definition,
Hyperfocal distance formula 2
For example, we are going to find the hyperfocal distance for a 35mm lens with its aperture set at f/8. Camera is a full frame DSLR.
For full frame DSLR, the Circle of Confusion value usually falls between .0291mm and .033mm. The value of .030mm⁵ is often used for 35mm film format and DSLR.
To convert millimeter to feet,
So what’s the meaning of this 16.9ft? This value tells us that at f/8, the depth of field from this point of focus is extended from some near distance to infinity.
That’s all about hyperfocal distance, folks. On my next post, I will blog about the depth of field scale and why it is related to the hyperfocal distance concept.
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Notes:
¹Sir William de Wivelesley Abney – (24 July 1843 – 3 December 1920) Born in Derby, England. Abney was an English astronomer,chemist, and photographer. Several technical aspects of photography were pioneered by Sir William de Wivelesley Abney. Dry photographic emulsion was developed by Abney in 1874, which later replaced the wet emulsions.
²Rudolf Kingslake - (1903–2003) Born in London, England. Kingslake earned a Masters degree in Optical Design at the Imperial College of Science and Technology. In 1937, Kingslake became the head of Optical Design department of Eastman Kodak.
³Hyperfocal distance – Wikipedia.
⁴Circle of Confusion – Also known as disk of confusion, circle of indistinctness, blur circle, or blur spot. The circle of confusion is used to determine the depth of field, often defined as the largest blur spot that will still be perceived by the human eye as a point. Wikipedia.
⁵Circles of Confusion for Digital Cameras.
