Focusing - Controlling the sharpness

Of all the ways of controlling an image, camera focus technique is one of the most important. Other aspects of an image may be perfect, but if it is out of focus by even a small amount, the resulting photograph may be useless. It is true that there are some photographs taken out of focus deliberately for novel or arty reasons, but most pictures suffer when they are not sharp.

Focusing may seem such a simple and common task to most photographers that they tend to take it for granted and minimize its importance. How to focus often, how to control the sharpness in camera photography or how to take sharp photo? Although seldom difficult, focusing can be made even easier if certain principles and techniques are kept in mind. Below mentioned some of the right way to focus in camera photography.

  • Rangefinder Camera - Focusing is easier with a rangefinder camera than with one using ground glass. However, most modern DSLR incorporate split image rangefinders and microprism collars into their ground glass viewing screens. Use whoever device seems most appropriate for the lens, the lighting conditions, and the subject at hand. The narrow angle of view of long lenses sometimes makes the split image rangefinder go dark in one half or the other and thereby become unworkable. On the other hand, it is often the only choice in dim light, where accurate focus with the ground glass alone is frequently impossible.
     

  • Lens wide open - With the lens wide open the resulting iamge is not only brighter and easier to see than with a stopped down lens, but depth of field is minimized so that the image snaps in and out of focus with greater clarity. Most modern DSLR's routinely open the diaphragm all the way after every exposure, but some older lenses must be used in stopped down mode in order for automatic exposure to work. Their diaphragms should be manually opened before any really critical focusing is attempted.
     

  • Faster lenses - When wide open, faster lenses produce even brighter images and shallower depth of field than slower ones. Focusing is made just that much simpler. However, there is a danger. If, after focusing, exposures are also made at the largest aperture, depth of field may be so shallow at closer distances that even though focus on the principal subject is accurate, nothing else in the picture will be sharp.
     

  • Longer Focal Length Lenses - With longer focal length lenses, as with fast lenses, depth of field is shallow, making it easier to tell when accurate focus is achieved. However, the bright image is missing. Longer lenses have relatively dim images because of their smaller maximum apertures. Regrettably, very long lenses may be slow (f/8 or f/11), and their images so difficult to see, that the advantage of their shallow depth is lost. Furthermore, because of the problem mentioned earlier in using a split image rangefinder with long lenses, focusing must be done on the dim ground glass. Accurate focus can certainly be attained in this way, but increasing care and precision must be used as focal lengths get longer.
     

  • Bright light - If there is plenty of light on your subject, there will be no dim, hard to focus viewfinder images even with long lenses. The brighter the viewfinder, the easier it is to see when the sharpest point of focus has been reached. However, when some older lenses are used in the stopped down mode, bright light may make it necessary to use small apertures, so it is even more important to open their diaphragms by hand before attempting any critical focusing. If you are indoors and find yourself having trouble focusing because of a dim viewfinder, turn on more lights, if possible or move to a brighter room. When outdoors move into a better light if you can, as long as the increased illumination doesn't interfere with the mood of your picture.
     

  • Subjects with distinct patterns and lines - Well defined patterns and clear cut lines give your eye definite points on which to focus. It helps even more if there is a sharp contrast in color and tone as well. Use a split image rangefinder on conspicuous lines - the edge of a building, a tree trunk, a book, or the edge of a person's face. Patterned clothing, a chain link fence, or a brick wall are easily managed by direct ground glass focusing. However, when taking portraits, don't be misled by easy focusing targets. A person's eye must always be sharp, even if other parts of the image are not.
     

  • Medium or Long distance - While there is less depth of field at very close range, which makes it easier to tell when the image is sharpest, focusing may require a tedious combination of adjustments involving both lens and camera positions. At longer distances the act of focusing is simpler, and the greater depth of field is very forgiving.
     

  • A stationary subject - A moving subject not only gives you less time to focus at any one distance, but its constantly changing position requires continual readjustment of the lens. Try zone focusing in this type of situation.
     

  • A sturdy camera support - If convenient, use a tripod or other solid support to immobilize the viewfinder image and make it easier for you to see fine detail. A shaky, hand held camera may cause the image to "swim" so much that the subject appears blurry even when it is correctly focused.
     

  • Lens Shielded from flare - Flare is caused by bright light entering the lens from the front or sides and bouncing around between the various elements. It washes out the image and makes focusing difficult. Use a lens hood, and try to point the camera away from bright light.
     

  • Auto Focus Camera - Except for occasional problem situation that requires manual focusing, an auto focus camera or lens relieves you of this burden. However, there is a danger that you may become addicted to this easy life and neglect opportunities for creative manual focusing when they arise.
     

  • If when focusing manually, overall sharpness in a scene is wanted rather than just a clearly defined main subject, focus on the subject first and then stop your lens down as far as possible for the lighting conditions. The same procedure is recommended when taking close ups and when the depth of field is very shallow.

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