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Old Aug 30, 2009, 8:34 PM   #1
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Default DOF Preview???!!!

I saw it in many camera review (indicates it's very useful!!!) it's also on my D300 but don't know how to use it or what's good for?

can someone enlighten me...thanks
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Old Aug 30, 2009, 8:45 PM   #2
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It stops down the aperture so your viewfinder reflects what the image should look like at the aperture you're using to take the photo.

Without using DOF (Depth of Field) preview, your camera is keeping the aperture wide open (at the smallest available f/stop number for the lens you're using). That way, you have a brighter viewfinder and your Autofocus Sensors can "see" to focus better.

When you take the photo, the aperture opening in the lens closes to where you had it set to (or what the camera's autoexposure algorithms have it set to if you're not shooting in a mode that allows you to control it).

The idea with DOF preview is so you can better judge what Depth of Field you'll have when the photo is taken (how much of the image is in focus as you get further from your focus point) by pressing and holding the DOF preview button.

It's a feature that I'd rarely use for anything, as it's a bit difficult to judge DOF in a small viewfinder (more of the image will appear to be in focus than actually is in focus). Some photographers like the feature.
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Old Aug 30, 2009, 8:48 PM   #3
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Depth of field preview lets you see what will be in focus and what will be out of focus, given the aperture you've selected, before you take the shot.

When you use a large aperture (numerically smaller), while the subject is in focus, objects closer to the camera and objects further away from the camera will be out of focus. As you select a smaller aperture, more of the foreground and background objects will come into focus. But the camera keep sthe aperture wide open so you have as bright a view as possible. The DOF preview does two things:
  1. The viewfinder becomes dimmer because the diaphram has been closed down to the selected aperture, letting in less light.
  2. Objects in the viewfinder that were out of focus before come into focus, showing you how the selected aperture affects which objects will be in focus and which will not.
Without it, you won't know how much of the foreground and background will be in focus until you see the resulting image.
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Old Aug 30, 2009, 8:49 PM   #4
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Oops.
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Old Aug 30, 2009, 9:12 PM   #5
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JimC and TCav thank you very much for the informative explanation.
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Old Aug 31, 2009, 12:03 PM   #6
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I think the DoF preview is a nice learning tool, but not really very useful beyond that. As TCav points out:
Quote:
Originally Posted by TCav View Post
... The DOF preview does two things:
  1. The viewfinder becomes dimmer because the diaphram has been closed down to the selected aperture, letting in less light.
  2. Objects in the viewfinder that were out of focus before come into focus, showing you how the selected aperture affects which objects will be in focus and which will not.
As the viewfinder becomes dimmer and dimmer it gets harder and harder to see the fine detail - which is what you are trying to preserve with a greater DoF. So ding about with it - you will see what changing the f/stop does, esp if you can keep looking as the f/stop changes.

You have to decide for yourself if you want to use it as more than an "Ah Ha!" getting device.
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Old Aug 31, 2009, 10:34 PM   #7
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I find very handy when I'm playing around in aperture priority mode. It gives me an idea what's in focus and what is not. I had the feature in my old film SLR camera.
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Old Sep 1, 2009, 12:33 PM   #8
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I often use the DOF preview for macro shots, or other situations where the inherent depth of field is shallow.
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