Understanding Depth of Field

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Depth of field (DOF) is the distance in front of and beyond the object that is in focus. This tutorial will teach you about how to use Depth of Field in your own photography.

A short depth of field can be very useful when you want to isolate your object from the background, such as when taking portraits or macro photography. A large depth of field is great when you photograph landscapes and overall when you want every detail to be in focus.

Control the Depth of Field

There are three variables that affect DOF, the size of the Aperture, the distance to the object and what lens you’re using. (There is a fourth thing that affects the DOF, but that’s the size of the sensor and unless you have two cameras with different sensor sizes this isn’t something to take into account.)



As you can see in the illustration above, a lower f-number equals a shorter depth of field. A higher f-number will give you focus over a longer distance — when you’re having a hard time getting the correct focus it might be a good idea to extend your DOF by changing the aperture.



The distance between you and the object is also important, the closer you are to the object the shorter the DOF. If you’re photographing a person but needs to have a high f-number you can still get a very short DOF by keeping the distance between you and the person to a minimum.



The last thing you can do to affect your DOF is to change the lens. A wide-angle lens has a much greater DOF than a telephoto lens; the most extreme wide-angle and fish-eye lenses don’t even have to focus because they are so sharp on every aperture for the entire DOF (making for excellent scenic shots).

It’s important to know that the depth of field is greater behind the object than in front of it. If you want to photograph, let’s say 20 kids standing in a line, and you want as many of them as possible to be in focus, but you’re unable to have a small aperture, you should focus on the 6th-7th kid in line, which would balance the field of focus about right (depending on your distance to the kids). If you would focus on the 10th kid, that is the one in the middle, the first few kids would be more out of focus than the kids at the back of the line.

Unlike some other parts of photography, the depth of field works in your favor almost every time. If you want to photograph landscapes you usually have a wide-angle lens — the object is far away and you use a high f-number — all these things together gives you a depth to infinity. And if you’re photographing macro you’re close to the object, you have a telephoto lens and often a low f-number — all these things will give you a very short depth which will make your object stand out and make the background soft and non-distracting.

A typical example of a photo with shallow depth of field control. (Only the main subject of interest is enhanced by throwing other elements out of focus.)



A typical example of a photo with extended depth of field control (From near to far in sharp focus).



Quick Reference Guide: Depth of field is governed by three factors: aperture, lens focal length and shooting distance. Remember the following relationships:

1. The smaller the aperture, the deeper the depth of field (the other two factors remaining the same). For example, if the lens focal length and the shooting distance stay the same, the depth of field is much deeper at f/16 than at f/1.4.

2. The shorter the lens focal length, the deeper the depth of field (the other two factors remaining the same). For example, comparing a 28mm lens with a 50mm lens at the same aperture and shooting distance, depth of field is deeper with the 28mm lens..

3. The greater the shooting distance, the deeper the depth of field. i.e. other two factors remaining the same). For example, if the subject is photographed from three and then from seven meters away, the zone of sharpness in the foreground and background is greater at seven meters.

Another characteristic of depth of field is that it is generally deeper in the background than in the foreground.

Sources:
http://www.mir.com.my/rb/photography/fo ... depth.html
http://www.tutorial9.net/tutorials/phot ... otography/

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What is Bokeh?

Bokeh comes from the Japanese word boke, which means "blur" or "haze", or boke-aji, the "blur quality." Bokeh is pronounced BOH-Kə or BOH-kay.

Visit any photography website or forum and you’ll find plenty of folks debating the pleasing bokeh that their favorite fast lenses allow. Adjectives that describe bokeh include: smooth, incredible, superb, good, beautiful, sweet, silky, and excellent… but what exactly is it?

Bokeh is defined as “the effect of a soft out-of-focus background that you get when shooting a subject, using a fast lens, at the widest aperture, such as f/2.8 or wider.” Simply put, bokeh is the pleasing or aesthetic quality of out-of-focus blur in a photograph.

Although bokeh is actually a characteristic of a photograph, the lens used determines the shape and size of the visible bokeh. Usually seen more in highlights, bokeh is affected by the shape of the diaphragm blades (the aperture) of the lens. A lens with more circular shaped blades will have rounder, softer orbs of out-of-focus highlights, whereas a lens with an aperture that is more hexagonal in shape will reflect that shape in the highlights.

Achieving Bokeh in Your Images

To achieve bokeh in an image, you need to use a fast lens—the faster the better. You’ll want to use a lens with at least an f/2.8 aperture, with faster apertures of f/2, f/1.8 or f/1.4 being ideal. Many photographers like to use fast prime lenses when shooting photographs that they want visible bokeh in.

You’ll want to shoot with the lens wide open, so you’ll want to use a shooting mode of Aperture Priority or Manual. Manual gives you the ability to choose both your aperture and shutter speed, whereas Aperture Priority allows you to choose the f/stop while the camera chooses the appropriate shutter speed for the exposure. You could also use the Flexible Program mode, choosing the widest possible aperture/shutter speed combination.

Don't worry if you don't own a very fast lens. By increasing the distance between the background and your subject, you can see bokeh in images that are shot at smaller apertures like f/8.

To increase the likelihood of visible bokeh in your photographs, increase the distance between your subject and the background. You can do this by decreasing the distance between the camera and subject. The more shallow the depth-of-field, or further the background is, the more out-of-focus it will be. Highlights hitting the background will show more visible bokeh too, so if you’re using a backlight, side light or a hair light, the bokeh may be more pleasing to the eye.

The most photographed subjects showing nice examples of bokeh are portraits. Close-up portraits show bokeh very well. Close-up and macro images of flowers and other objects in nature are also popular subjects to photograph that shows off bokeh in the image. An often-photographed subject that is an extreme example of bokeh is photographing a grouping of holiday lights or other highly reflective objects. When purposely photographed out-of-focus, these normally harsh or bright objects become soft, pastel, diffused orbs of glowing light.

Bokeh can add softness to an otherwise brightly lit photograph. Using this technique to separate your subject from the background can also allow you to utilize a not-so-photogenic background in your image—but because of its diffused blur, it helps to “highlight” the subject, not detract from it.

In this picture, Bokeh is easily seen in the foreground and background.



Source: http://www.nikonusa.com/en/Learn-And-Ex ... nners.html