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Old Jun 19, 2011, 12:44 AM   #1
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Default DoF Preview?

What exactly does this do? When I press the DoF button on the camera, the viewfinder gets darker, which from doing a dit of searching, results from the aperture blades on the lens closing to the designated F-stop. But my question is this....if that is true, when do the blades normally close? I thought that they would close as soon as a F-Stop were selected on the camera? So does it only close for the instant that the picture is being taken?
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Old Jun 19, 2011, 8:57 AM   #2
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The aperture isn't closed down until you actually push the shutter button, at least on modern cameras. With my model/manufacturer, there's a small lever on the lens that the camera operates when the shutter is pushed, to actually close down the aperture, otherwise the lens stays wide open. That's a really useful thing as otherwise you could be trying to focus through a very, very dark viewfinder!
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Old Jun 19, 2011, 11:45 AM   #3
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Cameras are designed to do their metering and autofocus with the aperture wide open, in order to have the maximum amount of light to work with. The DOF preview function is to let you check to see if all the objects you want to be in focus in the scene really are. As you noticed, though, when you do that, the VF gets pretty dark, and it is hard to see in the dim light what is in focus and what isn't. I have never found the feature useful, myself, though I seem to end up with cameras that have it, though I have read reviews that knock cameras for not having it.

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Old Jun 19, 2011, 12:48 PM   #4
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Quote:
Originally Posted by VTphotog View Post
... The DOF preview function is to let you check to see if all the objects you want to be in focus in the scene really are ...
... and to see if all the objects you don't want to be in focus in the scene really aren't.

I don't use it a lot, but I use it often enough that I would miss it if it wasn't there.
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Old Jun 19, 2011, 1:02 PM   #5
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Forget about it in the digital era.

A pre-shot is much better than DoF preview.
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Old Jun 19, 2011, 2:41 PM   #6
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Quote:
Originally Posted by big_potato View Post
Forget about it in the digital era.

A pre-shot is much better than DoF preview.
But you still have to scroll around on that 3 inch LCD screen to see what you could with just a DoF preview button.
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Old Jun 19, 2011, 4:33 PM   #7
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The 3 inch LCD is still a lot bigger than the itty bitty VF. I can't make out enough detail in the VF, especially if the lens is stopped down, to do me any good.

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