Depth of Field preview button

Discussion in 'General Technical Discussion' started by equetefue, Dec 2, 2005.

  1. equetefue

    equetefue

    489
    Sep 29, 2005
    Kissimmee, FL
    What does it do ? I read the manual and I hit it but don;t see a diference at all. I hear a sound but really can't see a diference. Is it that useful ?
     
  2. Ken-L

    Ken-L Guest

    When you use the DOF button, it "stops down" the view through the lens as it would appear when you take the shot. When you view through an SLR you are seeing through the lens, but always with it wide open (it's largest opening - lowest f-stop number). The smaller the opening, the greater the DOF. So, by using the DOF button, you will see how much DOF there is for your shot. Sometimes you need to try it in different light conditions before you can see the differences it shows. Lower light makes it more apparent.
     
  3. photosketch

    photosketch Guest

    When a lens is mounted on the camera, the lens is set to its widest aperture to allow for the photographer to view the scene and to allow as much light as possible for the AF to work. When one releasese the shutter button the mirror flips up and the aperture is stopped down and the shutter opens and closes.

    DOF preview will mechanically or electronically stop down that aperture while the mirror is still down allowing the photographer to judge the amount of acceptibly sharp focus is in the scene. As the aperture is stopped down, less light will be allowed into the viewfinder so the image will be dimmer. In great light, with practice, you'll be able to tell down to f/11 or f/16 how much of the scene will be in focus. In poor light, it'll be much harder.

    Try this with your D70 and 50mm lens.
    set f/1.8 and hit DOF preview. You should see no change as you are already at f/1.8; you should have very little in focus.
    set f/4 and hit the DOF preview. Now you should see a dimmer image and slightly more of the subject in focus.
    set f/8 - darker viewfinder, more of the area around the subject will be infocus
    set f/11 - very dim, allmost all of the scene will be in focus.

    I read that the best way to use the DOF preview button is to move down the range slowly, allowing time for your eye to adjust at each f/stop. (I got this from John Shaw's Close Ups in Nature.)

    Hope this helps.
     
  4. If you are seeing no difference then you are probably shooting at max appature and the preview button won't show you anything. Stop your lens down to f11 or so and try it again you will see the difference.
     
  5. MontyDog

    MontyDog

    Jan 30, 2005
    #1064 - You have an error in your SQL syntax;
     
  6. photosketch

    photosketch Guest

    p.s. Adding to Anthony's "allow eye adjustment time" I'll also add, if you usually keep both eyes open, this is one occasion when you have to shut the 'other' eye, and I find if I shut both eyes for a few seconds first, then open the VF eye - that helps too.

    Remember those ol' time view camera photographers circa the American Civil War who who stuck their head under a focusing cloth to block out all the light? Well, a focus cloth can help, too. doesn't need to be anything special, you can use a sweatshirt or jacket. Blocking all that light, keeping both eyes open helps to reduce the facial muscle strain.

    Regards,
     
  7. Baywing

    Baywing

    Feb 22, 2005
    CT USA
    Hey, Anthony, watch the old timer cracks!!!:biggrin: Some of us still use them old fashion rigs, and no, I don't remember the Civil War, I was too young then.......but my older brother......:rolleyes:
     
  8. photosketch

    photosketch Guest

    no offense meant...

    :biggrin: :biggrin: :biggrin: :biggrin: :biggrin: :biggrin:
     
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