DOF preview button question?

[Lightsped]

When I press the DOF preview button on both my D7000 and D800 (I don't think my D3100 has DOF preview), the viewfinder gets alot darker....

Is there a setting to keep the viewfinder from going dark when the DOF preview button is pressed?

I checked the manuals and was unable to locate anything....

 

[beachrat]

No they all get dark when you press the DOF preview,but I think a speedlight or the pop up flash will fire the modeling or assist light when you do.

 

[vimwiz]

Thats pretty normal - In the manual for my EOS it says thats to be expected.

 

[dxqcanada]

The DoF preview stops down the aperture. When that occurs the amount of light passing through to the viewfinder is lowered.
If the scene is bright enough you should still be able to view the scene to visualize what your Depth of Field is going to be for that aperture setting ... but if you are using a very small aperture you may not be able to see a lot.
Camera's with an EVF will automatically gain up the image to counter the darkening.

 

[KmH]

The DoF preview stops down the aperture. When that occurs the amount of light passing through to the viewfinder is lowered.

If you have an aperture smaller than wide open set.

Each smaller stop of aperture will reduce the amount of light in the viewfinder by 1/2 when using DoF preview.
Part of the problem is that a significant portion of the main mirror in a DSLR is 50% transparent to let light through to the secondary mirror that directs light down into the AF module in the bottom of the camera body.

Using a DSLR that adds to the light lost when the lens aperture is stopped down when using the DoF preview feature.

Or stated another way, because of auto focus, DSLR viewfinders are dimmer than SLR cameras that do not have auto focus.

 

[vimwiz]

Each smaller stop of aperture will reduce the amount of light in the viewfinder by 1/2 when using DoF preview.
Part of the problem is that a significant portion of the main mirror in a DSLR is 50% transparent to let light through to the secondary mirror that directs light down into the AF module in the bottom of the camera body.

Using a DSLR that adds to the light lost when the lens aperture is stopped down when using the DoF preview feature.

Or stated another way, because of auto focus, DSLR viewfinders are dimmer than SLR cameras that do not have auto focus.

I guess that applies to film too? My film EOS 300 (which can do AF, obviously, being an EOS) is significantly dimmer than that of my manual-focus T-70. I always thought maybe it was just due to being cheaper!

 

[bc_steve]

I believe when you are looking through the viewfinder, your lens is wide open. The DoF preview button closes the aperture to whatever you have selected, and if it's anything smaller than wide open, expect what you see through the viewfinder to be darker because of that.