Battle against Blur
A "new vision" for Photography or------! KEN RUTH
Photography has always tried to show us new ways of seeing. The medium is an individually adaptable tool for creating art.
Photography is a rare pleasure.
Lately some of us are individually encountering a new way of seeing that is unfortunately making picture creation irritating and difficult.
When we try to concentrate on creating a photograph we may be starting to worry about the condition of our equipment. Cameras you have been using for years now fail to consistently take sharp pictures as they once did.
Very likely you are having difficulty when focusing and have decided to get a new camera or a better focus screen.
Well hold on for a moment and consider this.
The sharpness and focusing problems may not be caused by your equipment but can result from the normal changes in vision that occur as we all grow older.
During the first year of our lives by contracting the muscles of the ciliary body, a structure that surrounds the lens in our eye, we can squeeze the lens thicker see details as close as two inches from our cute little face. We may not know what we are looking at, but at least we get the best view we ever will. As we "mature" the flexible lens in our eye gradually becomes stiffer and more difficult for muscles to deform when close objects greet us. The gradual age related hardening of the lens makes close vision gradually much more difficult to achieve.
By the time sixty candles appear on the birthday cake we may need an arm just short of six feet long to hold anything we want to read. Many of us first start to notice the loss of some close focus in our forties when minimum focus is frozen to over a foot away, and we can feel the ciliary muscles working hard to even get us that close. This natural change in vision due to ageing is called presbyopia. Presbyopia does not have to interfere with your ability to take sharp pictures, but it does require understanding and solving some problems first.
Distant relaxed focus happens to be a very individual thing for the average eyeball.
While one might assume a normal eye when relaxed would be happily focused on details at infinity, in reality relaxed eyes are individually set at all sorts of distances.
A near sighted eye is always focused closer than infinity and as a result can only see detail at greater distances by adding a corrective lens [read glasses] in front of it. For some individuals the relaxed vision distance can be very close. For others it may be nearly at infinity.
A farsighted eye relaxes it's lens to a focus that lies somewhere beyond infinity focus [does this mean they can still read Far Side cartoons when the rest of us can't?]. Farsighted young eyes by contraction of the ciliary muscles may achieve distant detail viewing, but eventual stiffening of the lens by age may at some point prevent any focusing of distant clarity. Once presbyopia. affects the lens of a farsighted eye, the eye will need separate correction for all distances from near to far. The interaction of the eye with the camera changes as the eye ages and each eye will eventually remain focused at only one fixed distance.
Now let's take a look in to the camera.
First; your eye when examining critical details, that the camera's lens focuses on the viewing screen, sees that viewing screen at some fixed distance from the eye. The apparent distance to the viewing screen can be fairly variable from camera to camera in how far away it seems to be.
A camera viewing system could be standardized to present the view screen to you at as though at a great distance, or just as easily by a slight design change, at two inches away. With few exceptions the distance that is presented to your innocent eye is fixed by the design of the camera. Selling a camera set at two inches would almost limit use of the camera to babies. setting the system to infinity would make use of the camera difficult for anyone with any degree of nearsightedness [which is a huge number of people] so it makes good sense to place the apparent distance at something like three feet more or less and allow the maximum number of younger adults with both nearsighted and normal vision to buy and use the camera. The problem is that as we lose our ability to accommodate [focus the eye on close objects] the limited range of distance, where our eye can see most sharply, probably will not match the fixed distance of a cameras focus screen.
Unfortunately the glasses we normally wear to correct our vision do not always help clear up the focusing problem with our cameras. The view screen distance is wrong for glasses that facilitate driving or reading. To have a correction that works with a camera the best solution is to take the main camera you use with you to your eye care providers and work with them to create a prescription appropriate for you and the equipment you are using. As cameras usually vary in the distance the viewing screen is presented to the eye, every camera may demand a separate lens prescription. Before you do take that favorite camera with you to the eye people you may want to give it a simple test just to be reasonably certain that there isn't some problem with that camera. To test the camera set the lens [preferably a wide angle lens] on infinity using the focus scale and make a steady photograph of a very distant subject that shows clear detail. If the test indicates good sharpness in the resulting image, the camera body is most likely not at fault for blurry pictures you are getting at other times. If you don't want to bother with glasses and still want to take sharp images [or if once again you forgot your glasses at home] you can still easily make sharp images without any problem. Rapid and accurate focus technique is a fusion of visual and kinesthetic awareness of the process of focusing. Obtaining sharp focus does not depend on actually seeing the image in sharp focus. As you focus, rather than seeking the sharpest point of focus. Keep moving the focus ring or knob in the same direction until a trace of increased unsharpness just appears. Stop at this point and reverse focus direction, moving again toward the sharper zone then past the sharper zone until the unsharpness increases again. Bounce your focus action quickly back and forth between the two points of increased unsharpness and then, using the kinesthetic memory of the movement, place the focus half way between the two remembered points of increasing blur. The faster you do this the better it works. Even with perfect vision this technique leads to quicker and more accurate focusing. With extreme wide angle lenses except for very close work [under 12 inches] it is also quicker and frequently more accurate to set the lens by the engraved focus scale, even if your eyes can focus on the view screen well. Beware of using the smaller apertures to gain huge depth of field to compensate for focusing difficulties. Increasing depth of field by stopping down can reduce the sharpness of the object that is actually in focus. Light diffraction can destroy resolution. To avoid destroying the crispness of a really great lens divide the focal length in millimeters by 4; the resulting number is the smallest safe aperture that does not rob the lens of it's best resolving power. for example a 200 mm lens divided by 4 yields 50 or f50 so lets say we can stop down to f45 and feel safe.
A 20mm lens divided by four indicates f5. As a final step; practice, start using your camera more, enjoy concentrating on creating images with greater ease, and explore your new " mature" way of seeing.
--------------------------------------------------------------------- KEN RUTH
Copyright 2002 Ken Ruth --All Rights Reserved.