Hyperfocal Focusing
This is a great technique for landscape photography. In photographing a landscape, you might want to get sharp pictures of all objects in your composition, starting from rocks, tress, bush, etc. below the horizon until the mountain fence, sky and other objects above the horizon. What usually do you set up your camera to get that composition? I set a small aperture f/16, f/22 or even f/36 and let the camera set the shutter speed automatically (or presetting first, if I want to use some filters). I turn manual focusing to infinity.
Your picture will be fine and you get a sharp picture of all objects, but wait a minute... There are some objects in the foreground that are not sharp. They are out of focus. Why is that? That's because the depth-of-field area spans from infinity to some point near you. This point depends on the aperture you choose, the focal length of the lens you use and the distance between the camera and the subject at focus (subject-to-distance).
Suppose that point is about 5m, then you'll get sharp pictures of a landscape from 5m to infinity. If there are no foreground objects closer than 5m, then everything is all right. How about if there is a rock/small bushes in front of you less than 5m? You'll get in trouble, because those objects are out of focus.
The depth-of-area spans between two points. The point near to you is called near focus limit and the point farther is called far focus limit. Somewhere in between the two points is your subject at focus. The portions from near limit point to subject and subject to far limit point is not equal. It's about 1/3 is in the front of subject and 2/3 is behind the subject. See the illustration below.
Now, by altering your lens focus manually a few meter closer, while keeping your far focus limit still in infinity, then you move your focal point closer and making all subjects from about where you stand to infinity, sharp. It is basically moving the depth-of-field area closer to you.
How far you can move your focal point manually while mantaining infinite far focus limit? Well, you can always guess or even use a hyperfocal distance calculator, but life is easier if your lens has a depth-of-field scale. You can just adjust your infinity mark on the aperture you chose and directly know the depth-of-scale area, i.e. where are the near and far focusing limit.
Furthermore your life becomes more complicated if you have a non full-frame camera, such as most common DSLR, because the depth-of-field area is reduced at the fraction of the camera multiplication factor. For example, my 350D has 1.6x multiplication factor, which means that the depth-of-field are is 1.6 smaller than what the lens gives.
Difficult doesn't mean impossible.
Links:
Your picture will be fine and you get a sharp picture of all objects, but wait a minute... There are some objects in the foreground that are not sharp. They are out of focus. Why is that? That's because the depth-of-field area spans from infinity to some point near you. This point depends on the aperture you choose, the focal length of the lens you use and the distance between the camera and the subject at focus (subject-to-distance).
Suppose that point is about 5m, then you'll get sharp pictures of a landscape from 5m to infinity. If there are no foreground objects closer than 5m, then everything is all right. How about if there is a rock/small bushes in front of you less than 5m? You'll get in trouble, because those objects are out of focus.
The depth-of-area spans between two points. The point near to you is called near focus limit and the point farther is called far focus limit. Somewhere in between the two points is your subject at focus. The portions from near limit point to subject and subject to far limit point is not equal. It's about 1/3 is in the front of subject and 2/3 is behind the subject. See the illustration below.
| <---------- DOF AREA ----------> |
| |
you ---> near limit ---- subject ---------- far limit
| | |
| <--- 1/3 --> | <----- 2/3 -----> |
Now, by altering your lens focus manually a few meter closer, while keeping your far focus limit still in infinity, then you move your focal point closer and making all subjects from about where you stand to infinity, sharp. It is basically moving the depth-of-field area closer to you.
How far you can move your focal point manually while mantaining infinite far focus limit? Well, you can always guess or even use a hyperfocal distance calculator, but life is easier if your lens has a depth-of-field scale. You can just adjust your infinity mark on the aperture you chose and directly know the depth-of-scale area, i.e. where are the near and far focusing limit.
Furthermore your life becomes more complicated if you have a non full-frame camera, such as most common DSLR, because the depth-of-field area is reduced at the fraction of the camera multiplication factor. For example, my 350D has 1.6x multiplication factor, which means that the depth-of-field are is 1.6 smaller than what the lens gives.
Difficult doesn't mean impossible.
Links:
- Hyperfocal focusing for better landscape photographs.
- A small section in Depth-of-field explained technique (look at under Everything Sharp section).
- Digital Depth of Field, esp. for using a non full-frame DSLR.
- Putting the Focus on Hyperfocal Focusing.
- Hyperfocal distance.
posted by Pak Sui at Thursday, May 26, 2005
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