Probably a dumb question...

[DiamondSCattleCo]

As I've been playing with the new body, I find myself confused by the depth of field preview button. I understand that its purpose is to review the depth of field, which is what every Google search has turned up, but I'm confused (I may have mentioned that already). When I push the shutter half way, the camera grabs focus, and as far as I can tell, gives you the EXACT same depth of field preview, except for the depth of field preview button often dulls down the viewfinder in poorer light. So whats the point? Or rather, what am I missing?

Buffaloed Rod

[Falconest174]

Which new body? As far as I have been able to determine, on my new D7K the preview button does just that,shows the DOF of the shot if taken at that time with that focus point. locked focus doesn't seem to do that as no change in the appearance of the image is visible. To my eyes it seem to work exactly as the old DOF method on film SLR's. It would dim the image as you are looking at the picture as it would appear to the sensor during the firing of the shutter.

[kgosden]

DOF preview makes the viewfinder darker because it closes the lens to the selected aperture. When you are focusing the lens is always at its fastest (largest opening) aperture so that the most light can get to the sensor/viewfinder making focusing easier on both man and machine vision. Well, that large aperture has the least DOF. So it is great when you want a distant background blurred, but not so hot when shooting macro or a long tele where the DOF might be millimeters or inches.

[Dread Pirate Roberts]

Good observation Diamond, the button is useless and is usually reassigned to some other function. I don't know anyone who thinks DOF preview is worth a pinch of sh.t