I have EOS 300. After going through various forums I find that lots of people mention about DEPTH OF FIELD PREVIEW BUTTON. What is it and where do you need button. I could not make use of that properly. Whenever I use it, I find that a blackish shade comes in the viewfinder as I increase the f-stops. What does that signifies ? Anyone who knows this would be deeply appreciate.

Thnx

-- sajeev (chack74@yahoo.co.in), December 19, 2001

Answers

You will want to press the DOF preview button when you have selected a small aperture setting for your exposure, and you wanted to see if the DOF is sufficent to cover your primary subjects.

When you look through your lens during focusing, you are actually using the largest aperture of your lens. However, pressing down the DOF preview button will close the aperture down to the actual size you've set for your exposure. Therefore less light enters the lens and you've have a darker view in the viewfinder. What you can do is to wait a while for your eyes get use to the darker view, then you'll be able to check whether if the aperture setting is appropriate for the scene.

-- Jason Poh (Jasonpgc@yahoo.com), December 19, 2001.

To add a little detail... Your camera leaves the lens at maximum (e.g. f5.6, f1.8, etc) apperture during focusing to ensure plenty of brightness in the viewfinder. However, maximum aperture also gives you minimum depth of field.

When you stop down (to say f11) for increased depth of field the lens aperture only changes when you hit the shutter button, so you don't see the effec of your change. If you use the DOP button it will stop down to your selected apperture. You'll see your real depth of field, but also a loss of light as the aperture is narrower.

DOP buttons are great, you've got to have one.

-- Marcus (Citizensmith@lanset.com), December 20, 2001.

thanks. after reading your comments i tried to look through the viewfinder with the DOF button depressed and changed the apperture. i find that as the apperture is reduced (large f-stops), more and more of the picture becomes visible i.e. the depth really increases. thanks again for your comments. i never used DOF in this sense. in future i will try to make a full use of DOF button.

-- sajeev (chack74@yahoo.co.in), December 21, 2001.