dibdab Loc: Newport, S.Wales

Having used manual lenses for many years I understand the concept.
My new D90 has a button just under the lens marked F of V
I've tried it in Auto and manual, and can't get a response. Can u explain. Regards

snowbear

It stops down the aperture so you can see what the field of view will be - the cameras keep the aperture wide open until you hit the shutter.

Try holding the button while you adjust the aperture ring - you should see things change.

GoofyNewfie Loc: Kansas City

That's called Depth of Field. DOF
"Field of View" has to do with the angle of the image the lens projects onto the sensor.
http://www.dailyphotographytips.net/camera-controls-and-settings/understanding-depth-of-field-preview/
The camera in the photo on the left is a D80 or D90.
The lower button is the DOF button.
The upper button is a customizable "function" button

snowbear

Dibdab:
Is this the button? If so, it id the Depth of View preview, as mentioned above. See page 82 of the manual.

source: D90 User's Manual

Gidgette Loc: Boerne,Texas

Yes, that's the button.

oldtool2 Loc: South Jersey

Using your Av setting set a shot at say f22. Press the button and change your f stop to say f2.8 while keeping the button pressed.

I shoot Canon so this may not work for you but on a Canon you can see the difference in the shot as you make the changes. It allows a preview of your shot at the settings you have chosen.

Jim D

rambler Loc: Masssachusetts

The change is often very subtle, hard to notice and often the screen goes darker which is the effect of the aperture. Look closely and especially into the background to look for the change.

dibdab Loc: Newport, S.Wales

Despite your comments I am still confused.With my 1962 Werramat( Zeis Jena Tessa 2.8 50 lens)I could work out DOF for all distances and from f4 through to f22.My D90 gives me date and time. Thats progress.
Focusing on a post 20' away with a 1.8 35 lens, I see no change in image up to f 3.4, then a diminishing brightness up to minimum aperture. What is it supposed to tell me?

rambler Loc: Masssachusetts

"Normally, your camera's iris is open as wide as it will go , regardless of the aperture choice you've made. This allows you to see a bright, clear view through the viewfinder. When you press the shutter release to take a picture, the iris is closed down to your desired setting, and then opens to full wide after the picture is taken. Obviously, this all happens in a fraction of a second.
If you have chosen a small aperture, the DOF in your image may be shallower than what you see when you look through the viewfinder. If you press your DOF preview button (after metering and setting your desired aperture), the aperture will close and stay closed as long as you hold down the button. This allows you to see the image through the actual aperture you will use. However, with the aperture closed down, your viewfinder will become much dimmer, which can make it hard to see your image at all, much less notice DOF.

Give your eyes time to adjust to the dimmer viewfinder, and if need be, cover your other eye with your hand to give yourself as dark a viewing environment as possible. As your eyes adjust, you should be able to get a better sense of the DOF in the image."

Ben Long, Complete Digital Photography, 4th edition, p.243

You might just take a few pictures at various apertures and check out the DOF results in the LCD.

rambler Loc: Masssachusetts

Whoops, the above refers to you "Preview Button" to view DOF.

Your Field of View should show you the difference between looking through the view finder and what you see in the LCD. For example, when I look through the viewfinder on my camera, I do not see a lot of the sky, or what ever is in the top of the scene that appears in the LCD and in the final picture.

NB Section 2 Field of View

http://mansurovs.com/equivalent-focal-length-and-field-of-view

jimni2001 Loc: Sierra Vista, Arizona, USA

Set your camera so you are just focusing on the center of the lens. If everything in the photo is in focus then you are not going to see much if any change. Then focus on something close where you are not on focus in the background. Then try pushing the button.