In our Complete Nature PhotoCourse we spend a good deal of time discussing hyperfocal distance and the importance of understanding the precise definition of hyperfocal distance in order to use a printed hyperfocal distance chart effectively. Let's look at the definition for hyperfocal distance first. It is:
The point of focus where half that distance to infinity is sharp. That means, if you're focused at a hyperfocal distance of 4 feet, two feet to infinity will be sharp. You focus at four feet, even though nothing may be there, but you know that if a foreground object is two feet away, or greater, it will be in focus and so will objects at infinity. If you focus beyond four feet, then infinity is still sharp, but you lose the minimum distance of two feet. Instead, it moves out towards four feet, and continues to move out the further and further you focus beyond the four foot mark.
Any given hyperfocal distance is specific for the lens and the aperture in use. Four feet may be the point of focus for a 24mm at f22 to acheive the true hyperfocal distance (half the focused distance to infinity) but four feet will not be the hyperfocal distance for f22 with a 50mm lens, nor will it be the hyperfocal distance for a 24mm lens set at an aperture of f8. With a 50mm lens set at f22, the hyperfocal distance is 19 feet (giving a depth of field that extends from 9.5 feet to infinity), and for a 24mm at f8 the hyperfocal distance is 12 feet (giving a depth of field of 6 feet to infinity).
You simply must know the definition and understand it to properly use a hyperfocal distance chart. If you don't, the set focusing distances given on a chart mean nothing. Why focus at these set distances? What does it accomplish? Why does the foreground object look unsharp through the viewfinder? Let's review the answers to the above as a final review. 1. The set distance is required to acheive true hyperfocal distance, from half the focus distance to infinity. 2. Doing so maximizes depth of field, IF you wish to achieve sharpness at infinity. 3. The foreground may not look sharp because you haven't used your depth of field preview button and you're looking at the image with the lens wide open. Closed down, as the image will appear on film, the foreground object would appear sharp if it half the distance from the focusing point, or greater.
Now, that's not the same as simply having great depth of field because, indeed, you can have great depth of field whenever you close down your lens to the minimum aperture opening (f16, 22, or 32 in most lenses). You will have your maximum depth of field when the lens is closed all the way down, but, depending upon where you focus, that depth may not extend to infinity, or anywhere close. For example, with a 105mm macro lens set at f32 and focused to 1:2 life-size, depth of field carries about one half an inch! If you focused on a green frog's eye as it faced you, the frog's nose would be out of focus, and so would its ear!
Some authors, indeed, some photo instructors, loosely or sloppily use the term hyperfocal distance when they are merely describing great depth of field. Worse, some folks suggest focusing a third of the way into an image to maximize depth of field, implying that you'll get infinity focus in doing so. That's simply not true. If you have a 75mm lens mounted on your camera, and your camera is rotated for a vertical format, it is conceivable that you could have foreground flowers that are four feet away in your field of view AND a distance mountain range at infinity focus. Both are in view, but neither end will be sharp if you focus 1/3rd of the way into the picture. By the way, what is 1/3rd? Is it 1/3rd of the way to infinity, is it 1/3rd of the way into your frame, is it dependent upon whether you have a low camera angle or a high? With a 75mm lens, at f22 the hyperfocal distance is approximately 42 feet away, so flowers four feet away would most certainly NOT be sharp. Your nearest flower that could be in focus would be 21 feet away?
For some of the above hyperfocal distances I used a neat little plastic card from www.synvis.com to state precise hyperfocal distances. Steve Traudt, the creator of the chart, offers plastic hyperfocal distance cards that will fit into your wallet or attach, via a luggage tag, to a camera bag, tripod, belt loop, or luggage. FotoSharp also makes hyperfocal distance aides, including a nifty slide rule type depth of field guide that gives the depth of field for a variety of lenses at various apertures at a variety of focusing distances. Remember the 105mm I cited earlier? Well, according to the FotoSharp guide, at f32, if your lens was focused at 3.5 feet, depth of field would extend from 3.25 feet to just over 3.75 feet. That's the lowest the guide goes, as depth just gets shallower and shallower the closer you focus and there is no point developing a chart when only your depth of field button will really provide you with a clue.
One final point. If you compare various hyperfocal distance charts or cards, you'll find that the actual hyperfocal distance may differ for the same lens set at the same f stop. This is because the developer of the card used different standards, called circles of confusion, to determine image sharpness and actual depth. If you wish to insure that you're always going to be sharp, regardless of which chart you use, consider using the hyperfocal distance for the next lower aperture, even though your lens is set for the smaller aperture. For example, use the hyperfocal distance for f16 when you are using f22, and by doing so, you'll be assured that everything will indeed be sharp. You may miss a little on getting your closest object as close as you might like, but you can be assured it will be sharp.
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