To say this wouldn’t fit in 140 characters is an understatement. Sorry for the long-winded post. Just takes some explaining…

I just got through seeing the Toy Story 1 and 2 in 3D double feature. Those that know me, already know that i’m a huge Pixar fan, so i won’t go into a long review of the movies. They are amazing, life changing events and you should see them (though amazingly, i think i was in the theater tonight with several people that had never seen either movie). This is more a review of the 3D-i-zation of the movies.

Interestingly i was both very pleased and disappointed. In that chronological order. I also made a discovery that i had often wondered about but never gotten the chance to test. It explains why i have always gotten a bit of a headache when i’ve watched just about any 3D movie.

First a little background: “Toy Story” and “Toy Story 2″ were, of course, not originally created for 3D presentation. They were originally created using 3D computer animation (“Toy Story” of course being famous as the first feature length all CG film), but rendered to flat 2D images for traditional exhibition. The great thing about this process is that, of course, Pixar still has the original files they used to create these movies so it was a relatively easy process to re-render the movies in 3D (after making lots of minor tweaks to lighting, etc). This means old movies in 3D, but in true 3D – not kinda hacked apart and “spatialized” like we’ve been hearing George Lucas threaten to do with Star Wars.

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That i could tell, no other major changes were made to the first movie. Obviously the detail in the picture was more apparent in a beautiful digital movie theater than on the old SD DVD release i have at home, but i didn’t notice any major re-working of backgrounds or textures, etc. If it was there it was very subtle. There was still a detail jump from Toy Story to Toy Story 2, as well there should be.

The practical upshot of them making no serious modifications to either movie was that a very ‘old’ and basic computer animated movie was thrust into the present and re-rendered in 3D. This meant that some of the more basic techniques used in that movie were preserved and stood in stark contrast to some of the more “advanced” techniques that were present in Toy Story 2. The most obvious of these differences, thanks to the 3D presentation, was artificial focal depth.

(We’ll take another detour for explanation…) When you take a picture using a standard camera (still or video), the lens system focuses at a certain depth. Objects that are much closer or much father away from the object being focused on will be blurry and out of focus. On the other hand, a computer generated image, like any artificial image, doesn’t naturally have any actual focal depth. Objects in the foreground, objects in the middle of the scene, and objects in the background are all perfectly in focus. So, when rendering the film, movie makers will create artificial focal depth and intentionally blur objects in the background and foreground to simulate the focal depth that happens naturally on a photographed (or filmed) scene in the real world. This is all well and good when the movie is being rendered down to a 2D presentation. We are used to seeing the blur of focal depth in 2D images on screen and it helps the scene feel more “real” – like it was photographed – and have much more depth perception than if everything was in perfect focus. A clear example of this artificial focal depth and how it is used to trick your eye into perceiving depth and scale can be seen on my Flickr stream using a process known as a fake tilt-shift.

So… originally Toy Story didn’t have much if any focal depth added. As you can see in the shot below, the details of the writing on the cardboard boxes in the far distant background are just as in focus as Woody’s face (see another example shot here).

Toy Story 2 on the other hand used the snot out of this technique of artificial focal depth, as it was all the rage and becoming common at the time of that movies production. It made for a more immersive and “real” feeling movie at the time. You can see an example below of the extreme focal depth blur added to this shot from Toy Story 2. It is most pronounced on the writing of the Buzz Lightyear box in the far right of the screen. (see another example here)

The trouble is: when you combine focal depth with 3D presentation, this equals headaches. Literally (for me anyway).

You see, the human eye is used to everything it looks at being in 3D, and everything it looks directly at being in focus. Simple enough. When you’re looking at a photograph or a traditional 2D movie, both of your eyes are seeing exactly the same perspective of that image and, though you can recognize depth in the shot, your eye/mind isn’t really trying to interpret depth since both eyes are seeing the same thing. However, in 3D your eyes are seeing different images. That’s how 3D works. Whether in the real world or watching a 3D movie, you perceive 3D because your eyes are seeing slightly different pictures. (Here is yet another example from my Flickr stream of basic 3D photography). 3D movies basically basically trick your mind into thinking you’re seeing a real scene, not a photographed image.

Thanks to the 3D perspective being provided by those fancy glasses, your mind expects to be able to look around “the room” in the shot and focus on whatever it wants. In “Toy Story” my eyes could do that just fine. No focal depth blur was added, so you could look around the room and your eyes could focus on the wall at the “back” of this scene and be fine with it. You percieve the depth in the shot because of the different images going to each eye, just like in the real work, but you’re able to focus all around the room, just like in the real world.

The trouble starts if you look off into the background and attempt to focus your eyes on objects in the distance, but artificial focal blur has been added, like the house in the distance of this shot. Your eyes assume they can look around this room where they are perceiving depth through different images like in the real world. But they can’t focus on the background. Try as they might to focus back there, the movie makers have made sure it will never work. As a result i had a headache through most of “Toy Story 2″, which never appeared in “Toy Story” and quickly left as soon as i walked out of the theater.

So there you have it. I have headaches because my eyes are trying to focus where they can’t and my brain can’t deal with getting “double” information on depth (different images to each eye on top of focal blur).

Sadly this means i will probably get headaches as i watch just about any 3D movie from here on out, unless the movie makers suddenly realize this issue and decide to make/render 3D movies differently in the future. I’m also not sure how movie makers are supposed to fix this issues for live-action 3D photography other than to use very short lenses with very broad focal depth so that most everything in the shot is in focus on the film.