In 3D, your brain does depth of field, having it forced upon you this way really makes it hard work to decipher the picture, especially if it’s moving.

I was particularly interested in the connection with games where shadows and light are used to draw focus to things, which as noted is a very old cinematographic technique.

In real life 3d then yes.

In "3D" on a 2D screen though surely everything is the same distance away from you and so your brain cannot do DOF when watching a 3D film.

Yes, but it's not presented as such, otherwise where's the point in using 3D.
Your brain is being forced in to 3D mode, so it does what it's trained to do, which is react to the visual stimuli in a real-life 3D manner.

Mark

Indeed - what happens is that your brain moves your eyes together until an object appears to be correct. It then judges a distance using triangulation and you perceive it to be in a point in space. If the image forces you to focus unnaturally on a certain point in space, you may experience discomfort. You certainly will be slower at adjusting to the image.

As the article I linked to states, a 3D composition should ideally be all in focus - with any highlighting done using shapes, colours or lighting. Because your eyes focus on the point they appear to converge, you get a natural depth of field. The trick is to make the eyes and brain react naturally to a scene, and give enough time for them to settle. If this means fewer cuts in a film, then so be it - that’s the nature of the medium.

I'm not sure that "natural DOF" would work though.

I realise that there is a perceived perspective and depth to the image giving the feel of a 3D world behind/in front of the screen but it only simulated and the actual image is in fact the same distance away from your face whichever part of it you pick.

Therefore there is no distance and close proximity for your eyes to focus to, it is all one plane.

The only "eye guidance" in terms of getting you to look in a specific area is to have everything in focus and use light. Even that way it will be odd though as you could be looking through some leaves of a tree towards a castle on a mountain miles away and both the leaves and the castle will be in perfect focus.

Slight thread hijack, but I was amazed at how 'cheap' this was, especially for Dixons:

http://www.dixons.co.uk/gbuk/samsung-le ... tor=ES-117

I'm not suggesting anyone buys a 3D TV though - it could rival that Betamax purchase if you made one

I was in PCWorld earlier today to get some photo paper and have a look at an iPad (just to see what all the fuss was about) and had a demo of the Samsung TV 3D System. They were showing Monsters Vs Aliens on Blu-Ray and I was very impressed with the effectiveness of the 3D as well as the picture quality. There's no way I would (or could) splurge £3000 on the system they were selling but it is something I'd consider if and when the price drops substantially and if there was a good library of 3D films to make it worthwhile. PCWorld also had a LG system showing football in 3D but I think there'd be headaches on the horizon with that.