It means taking a photo with the aperture at it's widest setting. If you can do this on your camera (you can't on automatic only cameras) you would do it by setting the aperture value to the smallest number it will go to. This will probably be different for different zoom settings..

Why would you do it? Shooting 'wide open' gives you the least depth of field. Which means that what you focus on will be sharp, but the background will be out of focus - an effect many want to achieve. However, it depends on your camera - even cameras with manual setting of aperture may not give much of a blurred background effect. Zooming in can help achieve this, and making sure your 'subject' (like a person) is well away from things in the background..

Androohttp://Androo.smugmug.com..

Shooting wideopen. that is at the lowest numerically fstop your lens has lets in the most amount of light(it is it's biggest hole), and at the same time generates the least dof. a situation in which you would want low dof is when you want the subject in focus and the background out of focus..

For dof info, see this webpage-http://www.dofmaster.com/dofjs.html..

Thank you for the response and explanation. Question: I am using the 2.8 70mm - 200mm Canon Lens. On a sunny day, is there a benefit of stepping down to 4.0 or 5.6 ? Do I increase the DOF? Any benefit to sharpness of my shot?.

Thank you..

If you want to isolate your subject, open up the lens to 2.8 or 3.2, but if you want the background to be in focus, close it down to 5.6 or smaller. Landscape and architecture shooters close it down to f/11.Wide Open @f/2.8.

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Closed Down @f/5.6.

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Or More @f/8.

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Hope this helps, Fredhttp://www.flickr.com/photos/fdevyatkin/..

Thank you very much for the examples. It answered my questions perfectly...

If you need the light to make the shot, then you have to leave the lens wideopen. but a wideopen lens does not give the best performance, it just lets in the most amount of light..

The lens, any lens, is at it's sharpest and gives maximum IQ at 2-3stops closed down from wideopen whatever fstop that is. OR rpt OR just put the lens at f8.0 if you do not know what fstop is the sharpest. me, I just use f8.0 and not worry about it..

Stopping down too much can also cause problems. beyond f11.0 diffraction distorsion begins. diffraction distorsion is what happens to light when it passes through a small hole, which is what a high numerically fstop is. does this mean that at f12.0 the image is distorted?, no. but diffraction distorsion is beginning. so if you go beyond f11.0 and need more dof than f11.0 gives do so.



Me, I find that f11.0 is giving me all the dof that need. note- that in a c sensor camera you are getting about 1 fstop more dof as compared to a FF digital or film camera..

For more dof info, try-http://www.dofmaster.com/dofjs.html..