Adjusting DOF in the Edit

[cameramandan]

Hi,

I remember in college a few years ago a lecturer told us that
there is a way to change the Depth of Field (i.e. shallow) while editing, I presume it would be highlighting the backround and defocusing it, or something along those lines. Just wondering has anyone come accross it, or even does it exist??

Cheers

[smiling sadly]

The editor did a bit of this in final cut pro on a music vid I did - mixed with a little overexposure and high contrast for a flashback effect. It worked as the entire shot was stylised but it was a little pixelly/grainy.

Other than that, I do not know.

[Jason Butler]

Assume it would be the same as with a still image. Mask off the area you don't want blurred and drop on some Gaussian or Motion blur to soften the rest. Problem is with motion and having to animate/move the mask. If it's not done right it'll be very noticeable.

This kind of a effect was very popular in music videos and adverts a few years ago. One that springs (pun) to mind was a Ballygowan advert with a horse and a red haired woman in a picturesque Irish town. And they obviously blurred / softened various parts of the image - usually around the edges of the frame. Not really faking a DOF shot but something more dreamy. Popped up (another pun) in Boyzone videos too.

[cameramandan]

is this tech used through Motion or after effects?

[sixgun]

After Effects is where I would do it. Use Lens Blur for more convincing results. If you want to go nuts you can create a depth map in photoshop to drive the effect or exract one from moving footage using optical flow software. Again only if you have the time/ desire to go nuts.

[Brian]

I think the whole movement in video thing could be a big problem. If it is a very still image or ECU it may be possible to mess around with a few programs, but really because the camera only takes in the light at the specific settings, the edit could look dodgy unless you use all sorts of effects and colouring to hide the job.

Sorry, don't mean to be negative, but focus is one this that is very difficult sort in post other than adding blur.

[MLM]

It really would depend on the type of shot. If it was a static mcu with the person a good distance from the background then isolating the background from the foreground using a mask and adding blur to the background would probably suffice. However if there are many elements in the shot and lots of movement then it will be more difficult. I think there is a 3D blur in Shake which might be useful. The issue with true DOF is it is 3D where as most Blurs in editing packages FCP, Avid etc are 2d. For example, with true camera DOF a persons eyes might be perfectly in focus, but their ears will be slightly soft and the progression from soft to hard focus is gradual. 2D blurs will have great difficulty simulating this gradual progression. I think this topic is an issue more suitable for visual effects artists and colourists, rather than editors.

Not sure how other apps life After effects would handle it but in combustion you use a DOF operator and G-Buffer combo, basically the way it works is that you paint gradient shapes onto your image, where say the darkest part of your gradient is at the back of the shot and the brightest is at the front. This is the G-Buffer, you can key frame the DOF to 'pull' from the dark part to the bright part. Obviously the gradients are only used as the control image, to tell the DOF operator where its working and how deep the space is. You can also do fog and other stuff like this. Shake has quite a similar way of doing it too. Hope this is of some help.

s