This is a way of ensuring everything in frame is clear and in focus without trying to 'sure' everything through the viewfinder - using the acceptable parameters of depth on the field on the lens.
By using the notches printed on the barrel of a lens, you can select your desired aperture (for example f22) and but the greatest distance (ie infinity) to one end of the f22 parameter, and the lens will notify you of the nearest point. Everything within that range will be sharp and crisp.
It's not very easy to explain - so this article may help, and the following pictures help me understand too.
(Taken from www.revellphotography.com)
If you are shooting landscapes you probably should. Have you ever wondered where to focus on a landscape to render the greatest area of focus from near to infinity? If you know how to figure out your Hyperfocal Distance (HFD), you will know exactly where to focus your lens.
So what is HFD? It is the point of focus that will give you the greatest acceptable sharpness from a point near your camera on out to infinity. The near point is half the distance to your HFD. The wider your lens and the greater the aperture, the larger the area of acceptable sharpness.
Every lens has a distance that can be calculated depending on the length of the lens and the aperture you are using. You might have noticed this effect when using a very wide lens where almost everything looks sharp as opposed to a telephoto lens which has a much farther HFD. This is because your HFD on a wide angle lens is very close to you when shooting at high f-stops so you will have more area in focus. It sounds pretty complicated but it’s really not. For example, you walk into a nice mountain range with a field of wild flowers in the foreground and you would like to get everything in focus. If you set your lens to f/22 and just focus on the closest flowers, the chances are that you won’t be sharp to infinity, which is where your mountains are. This is because you depth of field is determined by your HFD. Let’s say that you know that with your 24mm lens, your HFD is 3 feet at f/22. By focusing at a subject that is 3 feet away, you will be sharp from 1.5 feet to infinity.
Older lenses used to have this calculation right on top of the lens. All you had to do was line up the infinity mark with the f-stop you wanted to use and then look at the corresponding f-stop mark on the right side of the scale to see how close your acceptable sharpness would be to you. The mark in the middle would then show you where to focus to achieve that range, i.e, your HFD. Unfortunately new lens designs don’t incorporate this feature into the lens barrel (see below).
Maybe it’s because of the way the lenses are constructed or perhaps they just don’t think this kind of information is useful to today’s shooter. Whatever the reason, it’s a shame it is gone.
So what do you do if you don’t have a 15 year old lens? Well, there are a couple of options that you can turn to. For those of you that are big into slide rules (I know, I’m showing my age again), you can use a formula to figure out your HFD for all of your lenses.
So the hyperfocal distance for a 50 mm lens at f / 16 using a circle of confusion of 0.03 mm (which is a value typically used in 35 mm photography would be calculated like this:
All of that, just to figure out that you should focus at 5.2 meters. I know you are just itching to give that a try, especially when you are perched at the edge of the Rockies or some other great shooting location. No? Well then you can also try one of these methods -
The first is the “That looks about right” method of focusing about 1/3 of the way into your scene.
You can also use your camera’s Depth of Field Preview button to check your area of focus. This will give you some indication of where you should be focusing your lens. The problem with these methods is that if you focus past your HFD then you are cheating yourself out of some depth of field. If you focus in front of the HFD, you run the risk of not having your depth of field extend out to infinity.
So what’s the easiest way without going out to buy a bunch of older manual focus lenses or a calculator? Try downloading a chart which has done all of the calculations for you. The good folks over at Vivid Light Photography have gone to the trouble of creating a really handy chart that you can use for 35mm, 4×5, 6×6, and even DX format digital cameras.
You can get your downloadable PDF by clicking here. After you have downloaded the file, head on over to Vivid Light and read some of their great articles (including the one about Hyperfocal Distance). And the next time you are out in the field, try doing a little Hyperfocal Distance experimentation and see if you don’t get better results in your landscapes. But by all means, use a tripod.
