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  In itself the technique is one and only but there are many ways of obtaining acute against the blurred. All the methods are based on the use of lens with necessary focal length and precise adjustment of the acutance depth. In the last issue I wrote that camera lenses can have different viewing angles. Standard lenses view the world like a human eye. Wide-angle lenses have a considerably wider viewing angle; it can reach 180 degrees, i.e. draw a circle. Telephotolenses have a narrower viewing angle in comparison with the standard ones. There are lenses on sale which have taking angle of 1 degree.
All kinds of the camera lenses have an important characteristic. They differ in “depth of acutance”. This is a rather changeable characteristic of any lens. It is reasoned by the fact that optical system can’t depict details of the foreground and background with equal acutance. If you focus acutance on the grass near the camera lens, you’ll get blurred boundaries of the objects in the heart of the picture. If you focus acutance on the middle zone of the picture, you’ll get a blurred foreground and background in a varying degree. It’s clear that focusing acutance on infinity will cause blurring under your nose. The distance within which image seems acute is called depth resolution. Depth resolution depends directly on the focal length of the camera objective and aperture size. The less is the focal length, the higher is depth resolution. (Focal length of lenses is tethered to the film standard of a shot 24õ36 mm). The wider aperture is open, the less is resolution depth. In other words, to obtain the minimal acutance one should open aperture as wide as possible.
Displays of most modern digital not-reflex cameras are small and don’t provide good picture. It’s impossible to set acutance with their help. All the more it’s impossible to define the boundary between the acute and blurred in the shot. Owners of such cameras can use a formula by which they can rate hyperfocal distance. This intricate word sounds awfully scientific. In practice it means a “magic” spot before the camera lens. If one focuses acutance on this spot, all the space from it to infinity gets into the zone of satisfactory acutance. Besides, half distance between the camera and the hyperfocal spot will also get into this zone. Even first-former can calculate zone of depth resolution. The formula is as simple as omelet recipe. Focal length of objective should be divided by aperture value. For example: you have camera Sony 828 with integral zoom. You set the shot, look at the scale of focal length and see number 100. This is the focal length of your objective at the moment. Then look at the camera display. Let’s assume that it indicates exposure 1/60 sec at aperture value 8. Focal length 100:8 = 12,5 m. This is the hyperfocal distance. If you focus acutance on an object at this distance all the objects disposed in the distance from 6,5 m to infinity will be quite acute on the photo. I’ve got this result by taking half of hyperfocal length and subtracting it from 12,5 m.
You may ask me what happens with the depth resolution if you open aperture of Sony in full.
100 : 2,8 = 35,7 m. Hyperfocal spot has shifted from the camera to 23 meters, and depth resolution at open aperture is situated in 18 meters from the camera and to infinity.
Having known the secret of hyperfocal spot you may apprehend why cheep cameras with integral fully automatic optics produce such equally downcast acute pictures. Their lenses don’t adjust acutance. They are focused on the hyperfocal distance once and for all. They are doomed to obtaining maximum possible acutance.
Owners of more advanced cameras can change lenses or focal length of zooms by one’s own free will. They can focus zooms in accordance with their artistic goals, obtaining acutance which they want.
These are some examples of practical application of this technique for attracting spectators attention.
1. Use of macro lenses. These are special lenses for shooting small objects. Name of such lenses contains as a rule word “macro”. At shooting macro illustrations depth resolution of any lens becomes very low, and background, having fallen out of depth resolution zone, is blurred completely (See photo 4).