Depth of field in photography
Robert Meeks
One issue that certainly can generate any number of opinions to trying to present an appropriate definition is probably the depth of field. Whether defined as an area where objects are in focus or zone before the objects are outside focus, other than for the sake of argument, these changes in view do nothing to change the phenomenon itself. The aim of this article is to provide an understanding depth of field, but certainly not definitive, and to offer ways to take advantage of it to effect the creativity within our pictures.
When we focus the lens at an object, any point of light (in any part of the object is visible), which is at the point of focus is put on the table as a point of light in the plane of the film (or digital sensor). Any object that is not within the focus of the forms as a point of light before or after (in theory would shape) film plane. When the latter happens, but larger than the corresponding point of light is formed in the film plane. These points are called circles of light confusion (and what an appropriate name).
The circles of confusion are on the contrary out of focus and greater than the points of light that are in focus. However, if we reduce the size of the circles of confusion, the resulting image appears to be sharper. In order to reduce the size we need to reduce the diameter of light reaching the film. This is done by reducing the aperture (the diameter of the lens opening), which causes confusion circles effectiveness decreases in size, making them clearer. As we reduce our opening, we can improve the sharpness of these circles from our point of focus.
Although it might seem as if the more than close the opening, the sharper the picture will be, this is not the case when we are approaching a point where close the opening that the light begins to shift out of the leaves themselves. When this happens, the light that is deflected is shaped like circles of confusion over the plane film reducing sharpness in all ranges. Although still effectively have the depth of field, sharpness has been substantially reduced throughout the image.
We have an interesting effect on the other end of the opening range. When you open the aperture, a larger diameter, the circles of confusion, they become more big and lose even more sharpness. This has the effect of isolating the image is in focus to launch any object outside the range of focus out of focus. This also provokes an interesting game contrast as the contrast in the focus area is maintained, but the out of focus area is reduced contrast and saturation color. This adds to the effect of isolating a picture and use it in their favor is called selective focus.
The opposite of selective attention is the hyperfocal distance. This is the configuration into a lens when we want almost everything in a scene, about the date, to be acceptably sharp. If we set the goal of focusing at infinity, objects closer to the lens is out of focus and vice versa, if we focus on objects near the lens. We can do get everything (almost everything), near and far distance acceptably sharp by hyperfocal.
If our goal has DOF markings on the barrel, it is relatively easy to determine the hyperfocal distance. Set infinity in the opening in which we are skyrocketing. If you are shooting a f/11, set to infinity at f/11 DOF scale on our goal. The opposite side of the scale will now show the distance DOF focusing on the brand of f/11. The real hyperfocal distance will be the brand to focus on our goal.
If there is not such a scale on the lens, then we can resort to a standard of gold (which is much better than the algebra needed to calculate this). From our depth of field is reduced by 1 / 3 before our point Focus and 2 / 3 behind it, we want to establish our approach to the range twice that of our closest subject while using a small aperture like f/16. If your subject is closer than 15 feet, then we set the focus to 30 feet that put everything within the depth of field from infinity to 15 feet. This is working with a lens is 50 mm or less (for 35mm film) and a subject no less than 7 feet with this majority rule works.
This has been a brief introduction to some of the foundations of the depth of field. There is much more that can be studied on the depth of field and that I could have written. Since, however, I do not care for algebraic equations, when I am with my camera, general labor standards for me very well.
-Bob
This article is copyrighted 2005 by Robert Meeks. All rights reserved. Webmasters are allowed to use this article on your site, provided that the content of copyright and the information remains intact and a link is provided on the same page as the article, CargoShip Zhorkow's.
About the Author:
I have been involved with portrait and wedding photography professionally since the early 90s and been into photography since 1980. I presently write articles on photography and entertainment subjects as well do web design.
Article Source: ArticlesBase.com – Depth-of-field in Photography
The Effect of changing Aperture on your Camera (www.dombower.com)