Hyperfocal distance focusing (also known as Universal Focus) is that distance setting which maximizes the depth of field for a selected aperture. To understand what this means, we should define some terminology first – critical focus and circles of confusion. Bear with me here… although we can jump to setting and really using the hyperfocal distance setting, it would be good to understand the basic principles.
When a normal helicoid design lens is focused, there are no abrupt steps – rather, it is a continuum where the subject image being focused starts off blurred, and as the focus ring is rotated, the image slowly becomes clearer and clearer until it reaches the point of maximum clarity, and then, if the photographer continues to rotate the focus ring, the clarity begins diminishing slowly until the it becomes blurry and unfocused again.
In this continuum, the point of maximum clarity is the point of “critical focus”. On either side of this point of critical focus there is a region of “acceptable clarity” where the image appears reasonably sharp to the eye. This portion of the focus continuum where the image is acceptably sharp is the “Depth of Focus” for that lens.
If we imagine the continuum as a series of circles that reduce in size, at the point of critical focus, the circle is smallest and the image is sharp and clearly defined, as we move away from the critical focus, the circles slowly become larger, until the subject becomes blurry and then totally undefined. At that point, the circle is the largest. The correct name for these circles is “circles of confusion”. Years ago, manufacturers provided the minimum circle of confusion data for their lenses – for example 0.03mm etc.
Normally when we focus, we point the camera lens at a subject and rotate the lens focusing ring until the object is in critical focus. We are now guaranteed that the subject is now clearly defined, but what of the surroundings? Depending on the aperture setting, have differing depths of field. When we wish to focus at an object at a distance, we rotate the lens to the ∞ setting. Again, our depth of field is determined by the aperture setting.
If we choose a small aperture – f/16 or f/22, we are assured that we have a large depth of field, but a lot of the depth of field may be used inefficiently. We need to remember that the DOF is distributed unequally. 1/3 of the DOF is in FRONT of the subject, and 2/3 of the DOF is BEHIND the subject. If we are focusing on a subject at infinity – only 1/3 of the depth of field is really utilized, since everything behind the subject is already in focus by virtue of the ∞ setting.
What we can do to optimize depth of field is to set the critical focus at a point in FRONT of the subject, such that the subject is close to the far end of the depth of field. In short, we position the subject such that the maximum depth of field occurs in front of the subject, and a small portion occurs behind the subject. If we ensure that the infinity setting occurs just behind the subject, then every thing beyond that will ALSO be in focus.
If all this isn’t enough to digest, we also have to remember that distance to infinity (∞) for each lens varies – for a wide angle lens, ∞ setting could be just beyond 6 feet, and for a long focus lens, infinity settings could occur hundreds of feet away.
So much for theory. So how is this useful? Where can we use this?
As an example, let us assume that for a particular lens, the ∞ setting is around 30 feet, and we are focusing at a subject at just 30 feet away. If the lens is rotated to the infinity setting, the subject is clearly in focus, and we go ahead and take the shot without a second thought. Let us also assume that the possible DOF for this lens is 24 feet. From the previous discussion, we know that 1/3 of the DOF (8 feet) is in front of the subject. The 2/3 remaining DOF (16 feet) is unused, since everything beyond 30 feet is in focus anyway.
In the above shot, everything from 22 feet onwards will be in focus, but everything else between the photographer and 22 feet will be blurred. If we had set the lens at it’s hyperfocal distance instead of at ∞, the depth of field would have been fully utilized, with everything from 6 feet in front of the photographer to infinity being clearly in focus. What a difference!
In the above example, suppose we had been photographing a street scene. Or perhaps we were out trying to photograph a bunch of kids playing a pick-up neighborhood basketball game. Trying to critically focus on a particular subject would end up wasting a lot of time, and lots of blurry photographs. Street photography has to be quick, and opportunistic, and thus is a perfect application of hyperfocal distance setting.
Combine this with the Sunny f/16 rule, and we could just concentrate on the action, without worrying about metering, lighting, foregrounds, backgrounds, or what’s in focus and what isn’t. Every shot will be clear and in focus.
Despite all the mind-numbing theory we just covered, in actual practice, using hyperfocal distance couldn’t be easier. We just have to remember a couple of things — It’s best when used with a moderate wide-angle or normal lens (28mm, 35mm, 50mm etc). 24mm lenses have a very short ∞ setting anyway. Be sure to pick a lens that has a depth of field scale marked on it. Most of the older lenses have them. Modern AF lenses don’t generally have DOF markings, but there are calculation tables available. They’re cumbersome and not intuitive, but hey, it’s better than nothing. Here is a link.
The following steps assume that we are using a manual focus SLR like an Olympus OM-1, a Zuiko 50mm f/1.8 lens and 200 ASA film. It’s a sunny day, and we are out photographing a noisy and colorful summer street festival. Since it’s bright and sunny, let’s go one step further and use the Sunny f/16 rule as well.
Step #1 — Since it’s a sunny day, and we are using 200 ASA film, we will set the aperture on the Zuiko at f/16 and the shutter speed at 1/250 (sunny f/16 rule for a bright day with clearly defined shadows).
Step #2 — Once we have selected the aperture, everything falls into place. The same steps will be followed if we were selecting f/22 or f/11 or whatever.
Step #3 — Rotate the focus ring until the infinity ∞ mark is at the f/16 mark on the DOF scale. The distance indicated at the red index mark (5 meters about 15 feet) is the hyperfocal distance at this aperture.
Step #4 — Look at the distance indicated at the f/16 mark on the other side of the DOF scale – this is half the hyperfocal distance ( 2.5 meters or about 8 feet). At this setting, everything between the distances indicated between the f/16 index marks on the DOF scale will be in focus ie, between 8 feet and ∞.
The photographs will clarify the above….
|Lens focused at ∞
|Lens focused at 3m
|Lens at hyperfocal distance 5m (DOF ranges from 2.5m
to ∞ and thus encompasses both 3m and ∞ in
Thus we can be assured that everything on the street from 8 feet onwards (about ½ a parking space length) will be in focus, and we can be free to enjoy the action without fiddling around with the focus ring. Remember that filters will require additional aperture compensation when using the Sunny f/16 rule. If we are using a polarizer, the setting should be f/8 or set the shutter speed to 1/125 sec.
As far as lenses go, I have written this with the Zuiko 50mm f/1.8 prime lens as an example, but the best part is, any decently built normal or moderate wide angle will work as well as a hyperfocal distance lens – Zuiko, Vivitar, Kiron, Quantaray, Panagor, Sigma, Soligor, Albinar, whatever… just as long as it has a depth of field scale and can be stopped down to at least f/16. A short zoom can be used as well, if it has a depth of field scale. You’ll find it’s far easier with a prime lens.
If we choose not to use the Sunny f/16 rule, it’s even easier, since the camera’s TTL meter will compensate for the filters and indicate the correct shutter speed. Just set the aperture at f/16, and then follow steps #3 and #4. We simply adjust the shutter speed to what the meter advises, stand back to ½ the indicated hyperfocal distance point (8 feet) and shoot.
The same thing applies if we are using an OM-2. OM-PC or other camera that has an Auto setting. Set the aperture at f/16 or f/11. Rotate the focus ring as described in step #3 and let the camera set the correct shutter speed, stand back, and shoot. The hyperfocal distance will change for the larger apertures (f/11 and f/8) so we may not have as great a depth of field as at f/16. If you have to use filters, then shift to a 35mm or 28mm lens, for the greatest depth of field at the wider apertures needed.
Let the Summer street festivals begin!
text and images © 2007 ajoy muralidhar. all names, websites, brands and technical data referenced are the copyright or trademark of their respective owners.