Depth of Field

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Depth of Field




                                                                            
                                        Depth of Field: One of the most important elements in photography.

            Depth of field is the amount of distance between the nearest and farthest objects that appear in acceptably sharp
             focus in a photograph. A preferred selection Depth of field ("DOF") in a focused subject in an image can be quite
           subjective. Remember this, adequate selection of DOF for one situation, application may be unacceptable for another
               photographer. It is all a matter of personal preference when trying to determine the appropriate use of DOF to
                                                      enhance an effect in a photograph.




                                                                                                                     A typical
                                                                                                                     example of
                                                                                                                     a photo
                                                                                                                     with
                                                                                                                     shallow
                                                                                                                     depth of
                                                                                                                     field
                                                                                                                     control.
                                                                                                                     (only the
                                                                                                                     main suject
                                                                                                                     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


http://www.mir.com.my/rb/photography/fototech/htmls/depth.html[7/02/10 4:42:17 PM]
Depth of Field




                                                                                                                                                                                    sharp
                                                                                                                                                                                    focus )




                 You have to recognize the eventual effect of depth of field control that can bring to your photo but HOW TO ??
                                                          Simple, read on and digest.

           In simpler term, we define depth of field as the zone of sharpest focus in front of, behind, and around the subject on
           which, when lens is focused on a specific subject; with TTL (through the lens) SLR camera, DOF can be previewed in
           the viewfinder of a camera - the preview is very handy for critical type of work. For an example, when taking a product
           shot, when you require absolute certain if DOF is adequate to cover the object you intend to photograph Generally, the
           closer the subject to the camera, the more evenly with the distribution of depth of field in front and behind the subject.
           As distance of focus extends, DOF usually will be more behind than in front of the focused area.

            A few factors may have a direct relationship with depth of field, they are: 1) the diaphragm opening of the lens (the
                  Aperture), 2) the focal length of the lens in use, and 3) image size (it has a direct relation to distance).

            T h e   R e l a t i o n s h i p : The general rule of thumb for selecting the right aperture for a desired depth of field
           is: give the same object distance and the image size, the bigger lens opening (aperture) used (like f/2.8, f/2, f/1.4 etc.)
            will have a narrower band of depth of field - meaning critical focusing will be required in this kind of situation because
             when you use a large aperture (in particularly when focuses at a near to the subject), the zone of sharpness (DOF)
            can be very limiting; while on the other hand, if extended depth of field is required, you can just choose a smaller lens
             opening like f/8, f/11, f/16, f/22 to make the plane of sharpness is extended, so everything will be in sharper focus.


                                                                               Depth of field increases with distance. The farther you place the camera from your
                                                                               subject, the more depth of field you can obtain. Landscapes have great depth of field,
                                                                               while macro photographs tend to have very little depth of field because the subject is so
                                                                               close to the lens.




            <<<- -A wide angle lens combined with a smaller aperture should be good enough for great depth of field to register a crystal clear details from near to far. Copyright  - Free image
                                                                       collection 2000 . leofoo  Malaysian Internet Resources


            The "amount" of light allows to strike the film plus the duration (time) for the light to strike the film forms an exposure.



http://www.mir.com.my/rb/photography/fototech/htmls/depth.html[7/02/10 4:42:17 PM]
Depth of Field

            The camera has two mechanisms to control exposure, the lens diaphragm (lens section - aperture ) and the timing of
             the OPEN/CLOSE of the shutter curtain (camera section - shutter speed ). If this confuses you, the lens diaphragm
           (inside a typical SLR camera lens) consists of multiple blades which can be open and closed to certain size openings,
           the variations in the lens opening is called aperture. The size of the aperture determines the amount of light which will
           fall on the film. Various sizes of the lens opening are indicated by a set /series of numbers called f /stops or f/numbers .
              Each f/stop represents a specific quantity of light that pass through the lens. The smaller numbers are called large
                f/stops while the larger numbers are called small f/stops. This is because the larger numbers represent smaller
            apertures and allow less light to pass through the picture taking lens. Each time you move from one f/stop to the next
            smaller f/stop (larger number the amount of light allowed through is exactly halved. In effect, the amount of exposure
             itself is also halved. Using f/2 as an example, the amount of light reaching the film will change according to f/stop as
                                                                 indicated below:

                                                                                            
           f/stop                                   1.2*          1.4          1.8*        2          2.8         3.5*          4          5.6      8 11 16 22
           Brightness ratio                          3             2           1 1/4       1          1/2         1/3          1/4         1/8     1/16 1/32 1/64 1/128
           * Half f/stops.

             The largest f/stop on the lens is called the lens maximum aperture . The smallest f/stop on the lens is called
           the lens minimum aperture . The maximum and minimum apertures differ according to the lens-types. The maximum
            lens aperture is important because it indicates the largest amount of light that the lens will transmit through it to strike
                                                  the film "hiding" behind the camera shutter.

                                                           NOTE :- Certain camera/lens manufacturers have their lenses with the maximum aperture providing
                                                           half-f/stop reading rather than a full f/stop as printed on the aperture scale. Now supposing you have
                                                           the camera set for a certain exposure value ("EV"), say the exposure you get with f/4 at 1/60 sec.
                                                           You can recalculate other combinations (aperture and shutter speed) which will effectively give you
                                                           the same exposure as that above. As we use the above data as reference, some of these
                                                           combinations in the above example includes f/ 5.6 at 1/30 sec . and f/ 2.8 at 1/125 sec . You simply
                                                           move up and down the f/number and shutter speed scales as well as adjust the speed via camera
                                                           settings to achieve that.




                   Quick Reference Guide: D epth 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.


                 Depth of field decreases with increasing focal length (given equal subject distance) In other words, if subject
                   distance stays the same, a long lens gives less depth than a short. (A new theory emerges lately, indicating
                  contradictory report that focal length is depth of field independent, I have to find out this in real life application).


                                                                                                             One of the most used application is using Depth
                                                                                                             of Field control for portraiture photography. A
                                                                                                             clever photographer would use Depth of Field
                                                                                                             intelligently to emphasize a specific effect of the
                                                                                                             main suject of interest (in this case, the model) by
                                                                                                             limiting DOF away from confusing background via
                                                                                                             use of a larger aperture and/or using a smaller
                                                                                                             aperture to enhance the visual with pin sharp
                                                                                                             details from near to far (such as scenic, travel ,
                                                                                                             landscape etc.). Below are more examples. The
                                                                                                             photo at the left hand side is achieved with the
                                                                                                             intended result via combination of a long



http://www.mir.com.my/rb/photography/fototech/htmls/depth.html[7/02/10 4:42:17 PM]
Depth of Field




                                                                                     telephoto (300mm) lens + a larger aperture
                                                                                     (f/2.8).

                                                                                     <<<-- Oh.. Morris.(35k JPEG) leofoo  Malaysian Internet
                                                                                     Resources Copyright  - Free image collection 2000.




                                                                                                                                Another
                                                                                                                                example of
                                                                                                                                a shallow
                                                                                                                                depth of
                                                                                                                                field effect
                                                                                                                                for close up
                                                                                                                                as the
                                                                                                                                distracting
                                                                                                                                background
                                                                                                                                is "thrown"
                                                                                                                                out of focus
                                                                                                                                to draw the
                                                                                                                                viewer's
                                                                                                                                attention to
                                                                                                                                the main
                                                                                                                                subject.
                                                                                                                                Next,
                                                                                                                                remember
                                                                                                                                we
                                                                                                                                discussed
                                                                                                                                earlier:- the
                                                                                                                                nearer of
                                                                                                                                the subject
                                                                                                                                in focus to
                                                                                                                                your
                                                                                                                                camera,
                                                                                                                                depth of
                                                                                                                                field will be
                                                                                                                                more
                                                                                                                                "shallow".



                                                                                                                                This is the
                                                                                                                                OPPOSITE.
                                                                                                                                Maximum
                                                                                                                                depth of
                                                                                                                                field is
                                                                                                                                required to
                                                                                                                                show the
                                                                                                                                details of
                                                                                                                                the scene
                                                                                                                                that
                                                                                                                                attracted
                                                                                                                                my interest
                                                                                                                                and so, if I
                                                                                                                                want to
                                                                                                                                show the



http://www.mir.com.my/rb/photography/fototech/htmls/depth.html[7/02/10 4:42:17 PM]
Depth of Field




                                                                                                                          entire
                                                                                                                          scope of
                                                                                                                          the scene
                                                                                                                          from NEAR
                                                                                                                          to FAR in
                                                                                                                          sharp
                                                                                                                          focus. A
                                                                                                                          smaller
                                                                                                                          aperture is
                                                                                                                          used along
                                                                                                                          with a
                                                                                                                          28mm
                                                                                                                          wideangle
                                                                                                                          lens to
                                                                                                                          achieve the
                                                                                                                          objective.




                                                                                                                          It works on
                                                                                                                          other usage
                                                                                                                          such as
                                                                                                                          dealing with
                                                                                                                          scenic,
                                                                                                                          candid,
                                                                                                                          portraiture or
                                                                                                                          even street
                                                                                                                          photography.


                                                                                                                          Here is
                                                                                                                          another
                                                                                                                          example of
                                                                                                                          smaller
                                                                                                                          aperture is
                                                                                                                          used on the
                                                                                                                          lens section
                                                                                                                          for
                                                                                                                          MAXIMUM
                                                                                                                          depth of field
                                                                                                                          to ensure all
                                                                                                                          the elements
                                                                                                                          are in focus.




           There are times when you need to affect the amount of depth of field for a particular scene. In a scenario like low light
           where you need to to shot wide open and wish to have extended depth of field or cases where you are force to live


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