Extremely shallow depth of field

[William Middleton]

My apologies if this is a dumb question or has already been covered--does anyone know how the extremely shallow depths of field are attained in modern feature films today? This 'style' seems to be very popular at the moment; I've seen it in a number of films recently, one of which is 'Side Effects'. There were even a few moments in the movie where everything in the scene was out of focus until the actor moved a literally just a few inches and came into focus. What exactly is causing this interesting effect? Is it a particular Lens? Camera? Some combination of the two? Is it a result of newer lens/camera technology or has this type of DOF always been possible?

[Travis Gray]

Check out a depth of field calculator online or an app (probably should just link to one: http://www.dofmaster.com/dofjs.html)

 

It's a combination of focal length, aperture, and sensor size.

 

Big sensor, long focal length, and wide open aperture gets you a shallow depth of field, plus distance to object factors in as well.

 

So on a Super35 sensor, 85mm, f/2.8, and 5ft away = .14ft (too lazy to convert haha) depth of field.

[William Middleton]

Thanks. That helps alot.