Stupid question: where does the illusion of 3D come from?

A couple of weeks ago, I took some shots at the Ripley's Aquarium. A few of the Jellyfish shots surprised me in how 3D they looked even though I used my regular 70D and regular settings. So I thought I'd ask, what results in this illusion of 3D in what is just a 2D shot? Also, can this be a subjective think because my wife did not see it while I noticed even on the LCD on the back of the camera.

Here is an example of the shots in question:

https://www.flickr.com/photos/pritzl/15648176563/in/set-72157650272489035

Sit in front of a big window and take a photo of someone looking right at the camera.  The light is even all across the face than the face will have a flat appearance in the photo.

Now move off about 45º to the side and have the subject turn their face about 35º toward you then turn just their eyes to the lens and take a photo.  The face will now have a side that is directly lit by the window light and a side that only has indirect light on it, the face will have highlights and shadows and take on a 3D appearance in your photo.

Want to make your jelly fish image look even more 3D?  Take the lens out of one side of an old pair of sunglasses, put the sunglasses on, and look at the image.  Now try that with TV.

You are fooling the brain with the different amounts of light to each eye for the same subject and it processes the visual information to give the flat image a nice 3D appearance.  Don't leave the glasses on very long or the brain gets used to what you are doing and the 3D appearance goes away.

So in this instance, did the flat background lighting and the varying colour intensity across the jellyfish's body create the illusion? I have since asked a few more people and each perceived the effect to a different degree so, to some extent at least, it does appear to be subjective.

Yes, the eye perceives lighter, more in focus parts of objects to be in the foreground, and dark fuzzy objects in the background. Also shadows add to the perception of roundness, and therefore depth. Objects below midway down an image are assumed to be closer to you as well, though in this case that doesn't make a difference. Different colors have different wavelengths and can also influence depth--and, no two people see the world the same way in 3D, and some not at all. There are algorithms for creating 3D from 2D that use all these perceptions and more. I had a friend who lost vision in one eye and could "see" in 3D by wiggling his head from side to side. His brain, in turn, would fuse the two images into 3D--so he said.

This article says it all, I think...

http://en.wikipedia.org/wiki/Depth_perception

Thanks for the response. Just to make sure I have it straight: I get the 3D impression from that photo because:

1. Narrow depth of field centred on the closest edge of the jellyfish's dome makes it look closer than the rest of the jellyfish's body.
2. Colour contrast between the jellyfish and the background.
3. Colour and light/shadow contrast within the jellyfish itself adds to its rounded appearance.
4. I must be really sensitive to these factors to get this overwhelming perception of 3D from this particular image.

Sound about right?

threed123 wrote:

Yes, the eye perceives lighter, more in focus parts of objects to be in the foreground, and dark fuzzy objects in the background. Also shadows add to the perception of roundness, and therefore depth. Objects below midway down an image are assumed to be closer to you as well, though in this case that doesn't make a difference. Different colors have different wavelengths and can also influence depth--and, no two people see the world the same way in 3D, and some not at all. There are algorithms for creating 3D from 2D that use all these perceptions and more. I had a friend who lost vision in one eye and could "see" in 3D by wiggling his head from side to side. His brain, in turn, would fuse the two images into 3D--so he said.

This article says it all, I think...

http://en.wikipedia.org/wiki/Depth_perception

In line with what you are saying, I just built a slider for my video camera. By sliding the camera while filming the impression of 3d is amazing. Videographers have know this for some time. Panning the camera does not give the effect because the perspective does not change. Moving the perspective of the view, just like your friend did, gives the brain enough information to create a pseudo 3D view. There was an inventor several years ago who was trying to sell being able to get 3D video by having the perspective dithered in the camera. It never took off.

Thank you for the compliment. I'm trying to make it deliberate rather than fortuitous.

It's a well recognized effect that warm colors tend to advance, while cool colors recede for many observers.  Try reversing the colors and see what changes.

Interesting. I will try that. Thanks.

crunchy_3d wrote:

Pritzl wrote:

A couple of weeks ago, I took some shots at the Ripley's Aquarium. A few of the Jellyfish shots surprised me in how 3D they looked even though I used my regular 70D and regular settings.

I can't see even a hint of 3D, but your pictures are beautiful, even though they are in 2D.

Try to make them 3D next time!

Damir

I think it is a subjective impression as suggested above. Thanks for the compliment though. I try.

Turbguy1 wrote:

It's a well recognized effect that warm colors tend to advance, while cool colors recede for many observers. Try reversing the colors and see what changes.

+1

Or more pure intense colours tend to come forward and more mute colours receed.

If I remember correctly this is one of the things that people say about the famous painting "Blue Boy". And some say it was in response to a painting of a boy that was wearing a more red / pink suit.

I think this images works because of the high saturation of both the red and blue colours. They seem to vibrate with intensity.

That and the fact that there is a lot of detail in the jelly fish, but no detail in the background, so it forces your eye to really concentrate on the jelly fish.

Great image! I love it!

Take care & Happy Shooting!