How do you use the Depth of Field Preview button on a Nikon D90?

Question

I am trying my hands around using Depth of field preview button with my Nikon D90 and its 18-105mm Kit lens. I read some online material as well have seen some videos about using it, but so far I'm not having any luck.

I've tried the following:

1. First i set my aperture to 5.6,focused on some object 5-6 feet away adjusted the light meter and than pressed the DOF button.
2. Again changed the aperture to 11 with same steps than to 22 with same steps.

I don't see any changes when I do that, though. Now this means either I am really dumb (:)) or i am missing something. Can any one help me figure this out?

Answer

I hate to say this, but first make sure you're pressing the right button, as I always press the wrong one. There are two similar buttons. One is the function button near the top of the lens, and the DOF preview button is almost under the lens.

If you press the DOF button, even with the aperture wide open, it will make a very clunky sound, like when you press the shutter and the mirror bounces up.

At f/22 the image through the viewfinder should get much darker.

I'm pretty certain you can't reprogram that button on the D90.

Edit: picture worth 1000 words! This is a D80, but button is in the same position (from digitalreview.ca)

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