D.O.F. advice please

[plumb]

I have just upgraded from a canon SI IS to Nikon D70s and have never used a D,O F preview button before,can anyone explain in layman terms exactly what I do and what to look for,any help would be greatly appreciated

[jamison55]

Now that you have a DSLR you'll find that you have to work a little harder to make sure that everything is in focus. That's what DOF is. Very simply, how much of the area is in focus. It is directly related to the focal length of the lens, the aperture you choose, and your distance from the subject. For example f2 on a 50mm lens when your subject is 10 feet away will give you a few inches of properly focused image. F8 will bring much more of the subject in focus, f16 even more and so on.

Here's the problem. As you close down the aperture the image in your viewfinder becomes darker and darker, making it more difficult for you to see the image. Modern SLR cameras get around that problem by leaving the aperture wide open until you actually click the shutter. This is nice because your image stays bright the entire time you are viewing it, but it doesn't help when you are trying to determine if enough of your image is in focus (since you are viewing the image at the widest aperture always). The DOF preview button stops down the lens while you are looking through the viewfinder allowing you to see how much of the image will be in focus when you actually take the picture.

Give it a try. Look through the viewfinder at an object a couple of feet away at your lenses widest aperture. Then stop down the lens to f8 and look at the same object while pressing the DOF preview button. You should see more of the image in focus.

On my Canon DSLR's the DOF preview button makes the flash light up for a couple of seconds. I use it all the time to help women find their earrings on the dance floors at weddings!

[erichlund]

Now that you have a DSLR you'll find that you have to work a little harder to make sure that everything is in focus. That's what DOF is.

Or, and here's a big advantage, keep only the subject you want in focus and blur the background.

Cheers,

[plumb]

thanks to both of you for your replies,I have now got the idea how it works