The Stereoscopy Glossary
Stereoscopy is a very technical art form. While there are lots of opportunities to be creative, there's also a lot of lingo and technical terms floating around.
Here's a handy dandy glossary of some common ones, with some links to help you along
A
Accidental stereo effects
This is a strange effect that you notice when you create a stereographic photo which has repeating pattens in it. It happens because the pattern isn't 100% perfectly identical all the way along, and the slight differences in shape cause it to appear as if it's in a different place from the parts of the image around it. Postage stamps, wallpaper and other things with patterns tend to cause this effect.
Accommodation
Accommodation is when the eye refocuses from one object to another when your vision shifts (like looking through a window on a rainy day, you can focus on the raindrops clinging to the glass, or on the landscape outside).
Active stereo
This is a method of stereo in which you need special glasses to view left and right eye images in rapid succession. Shutter-glasses are a form of active stereo technology.
Anaglyph
This is a stereoscopic image or video viewed with colored glasses which block out a certain color from each eye, then used to create the illusion of depth.
Autostereogram
A stereogram which can be viewed without the aid of any equipment, like a side by side or "magic eye" type picture.
Auto-stereoscopic
Stereoscopic viewing without glasses.
B
Base (Stereo Base)
This is the distance between the centre of the left lens and right lens used in a stereo pair. Conventionally this would be your interocular distance (about 6.5cm), but this isn't a very strict rule.
Baseline
This is simply the distance you move between taking the left and right pictures of a stereo pair.
C
Cha-Cha method
Using an ordinary camera to create a stereo pair by taking a photo, moving slightly to the side and taking another photo.
Convergence
This is the ability to focus both your eyes on a fixed point in space (usually close to you).
Cross-eyed viewing
Viewing a pair of stereoscopic images (or an autostereogram) by crossing the eyes to look at a point in front of the screen.
Crosstalk
Mostly in methods using glasses, this is when the two images of the stereo pair aren't separated properly and bleed into one another, breaking some of the illusion of depth in the image.
D
Depth Budget
In an animation or film, you use the size of the screen and the resolution if your film to work out the maximum distance you can have between the objects closest to the viewer and furthest away.
Depth Perception
Depth perception is our ability to judge how close or far away an object is by looking at it.
Depth Script
This is a type of script used for a film or animation, which describes how much or little stereo depth there will be in the scene. Looking at stereoscopic film for a long time hurts your eyes, so the idea is to use it only when needed. For example, a scene with people talking might actually be quite shallow and pretty much 2D, whereas a fight sequence with lots of explosions that need to pop out at the audience will be a lot deeper.
Diplopia
A fancy word for ghosting (where you see both the left and right images faintly at the same time because they don't overlap to form a single stereo image correctly).
Divergence
This describes the eye's ability to point outwards. It's the opposite of crossing your eyes. It's really painful and should be avoided.
F
Far point
This is the point where the furthest object from the viewer is.
Floating window
This is quite a recent idea, where one of the images is cropped in a stereo pair to make it look like the "screen" is moving in space. It's useful when you have people or objects which should be in front of the window crossing over the side of it.
Free viewing
A method of displaying and viewing stereoscopic images without the need for glasses or special equipment.
Fusion
This is when a stereo pair merge to show a single stereo image.
G
Ghosting
This is a common issue in stereoscopy when a stereo pair does not align properly and you can see a faint double image of both left and right eye images at the same time, and usually hurts to look at.
H
Holography
This is a technique of creating a 3D illusion in real world space, usually using some sort of laser and smoke or haze that it can shine through.
Hyperstereo
The effect caused when you exaggerate the distance between your stereo pair when creating a landscape image. It makes your photo look like it's comprised of miniatures, but creates a better sense of depth.
I
Image Splitter
Because you sometimes need to use two cameras to take a stereo photo and the distance between them can't physically be as small as you need it to, you would use an image splitter, which allows you to take a stereo pair of photos with a smaller distance between them. This is also used when you only have one camera and need to take two photos, it can split a single image into a stereo pair.
Interocular
This is a very fancy name for the distance between your eyes, on average about 6cm.
L
Lenticular
Lenticular describes a type of stereoscopic image which alternates the left and right eye images in little strips, and is covered with a special type of sheet that hides certain angles from your eye. This means you get only the strips with the left image visible to your left eye, and the strips with the right image are visible to your right eye.
Lorgnette
Lorgnettes are actually the word used to describe opera glasses, the ones on sticks you hold up to your eye. Stereo lorgnettes are glasses with strange warped lenses which help you see side by side stereoscopic images. They're actually quite difficult to use, because you need a specific size of image at a specific distance from the glasses to make them work.
M
Macro stereo
This is an extremely close up stereo image where the interoccular has been adjusted so you can make out a reasonable amount of stereo 3D.
Magic Eye
This is a series of books which publishes pictures of autostereograms (that random pattern looking thing which you can stare at to see a hidden picture). The correct term is autostereogram, "Magic Eye" only refers to that specific company and their books.
Misalignment
This is what we call it when your stereo pair of images don't line up properly and everything is very hard to make out in stereo.
N
Near point
The fancy name given to the point in your picture or film where the closest object to the viewer will be.
O
One-in-thirty rule
Ok, this is a bit of maths, but don't freak out. The one in thirty rule simply says that you'll get the best stereo depth by making the distance between the stereo pair you have 30 times smaller than the distance between your camera and the subject you're looking at. It's not gospel though, and there's lots and lots of exceptions to this rule. Know it's there but don't get caught up calculating it.
Orthostereoscopic image
This is an image where the depth is perfectly matched with what you'd see in the real world.
P
Parallax
Parallax refers to the difference between the position of objects depending on the angle you look at them from. It sounds really complicated to explain, but there's an easy way to think about it. Hold your index finger outstretched in front of you and look at it. Cover or close one of your eyes. Then open it and close the other one. You will notice that your finger now looks like it's in a different place compared to the things in the background. This is parallax!
Parallel viewing method
Viewing a pair of stereoscopic images (or an autostereogram) by relaxing the eyes and looking straight ahead (as opposed to crossing them).
Passive stereo
A method of viewing 3D content with glasses which aren't mechanically doing anything. Usually this means you're using glasses which are polarised to block half the light in each eye and filter the correct images to the correct eye. You need special displays to view passive 3D, but it does mean that the glasses you wear for it are very cheap and easy to come by. RealD is a form of passive stereo.
R
Retinal rivalry
This term is used to describe what happens when you look at an incompatible pair of images. The left eye sees one thing, and the right eye sees another which can't be converged into a stereoscopic image (because it's not), and your brain gets very confused. Try looking at two different things, one with each eye, to see the effects of retinal rivalry, it can really hurt. This can also occur when your stereo pair is too far apart and doesn't converge correctly.
S
Shutter glasses
Shutter glasses are a type of special glasses which can electronically turn opaque so you can't see through them. They let you watch stereo films by quickly opening and closing each eye's "shutter" and flicking between left and right eye views very fast on the screen, so fast in fact, that your brain can't tell and just sees the film.
Stereo blind
Stereo blind is the description of someone who, for whatever reason, can't see stereoscopic images. They can usually still see wiggle stereo though (because it's not one image sent to each eye).
Stereo infinity
This is the furthest point in a stereo image where you can tell the depth of something. Everything behind this doesn't really have depth any more. A ballpark figure is usually about 200m.
Find out why here. Warning: Link contains MATH and head may explode as a result of clicking.
Stereo pair
This is simply a pair of images which combine in some way to create a stereoscopic image. This of course means that each stereo image is made up of a stereo pair.
Stereogram
This is the broad term for any image, film or otherwise which have a left eye view and a right eye view which combine to create a stereo image in any way.
Stereographer
The name given to someone who creates stereoscopic content.
Stereography
The name used for the process of making stereo images and films.
T
Toe-in
To toe-in is to make the focus of your stereo pairs exactly where you want screen depth (the window) to be. For example, if we have a box with a sphere behind it, and we toe in so both our images point to the sphere, the box would be popping outside the screen. However, if we focus on the box, the sphere would be deep inside the screen.
Twin Camera Set-up
This is a method of taking a stereo photo using two cameras at once. This may sound like an odd thing, but it's pretty important when you need to capture something quickly. For example, if you want to take a photo of a ball flying through the air in stereo, you can't take two photos one after the other. A twin camera set-up means you can capture action in your stereo photos!
More Info here.
Twist
This is how you describe two images which should form a stereoscopic image, but one of them is rotated sideways and doesn't match up. It's a good idea to make sure you don't have any sideways rotation between your stereo pairs.
U
UFO
A UFO isn't a little green alien. In terms of stereoscopy, it means "uncomfortable fusion objects". It's the fancy title given to something that hurts your eyes when you try to see it in 3D.
V
View-Master
View-Masters are those old fashioned red glasses things that you put up to your eyes to see a stereoscopic picture with!
Virtual Reality
Virtual Reality (or VR) is a term that's used for digital environments which can make you feel like you're really in them, be it by looking around, being able to touch things with your hands, or being able to walk around without needing a keyboard and mouse.
W
Window
A stereo window is the position where the actual screen is. Everything that is stereoscopic and looks like it's inside the screen is "behind the window", and everything in front of it is "in front of the window". When looking at an anaglyph image, you can usually tell if something is sitting in front of the window, because the blue and cyan fringe colours will be flipped for the part of the image that sticks out.
Window Violation
When an object which should be popping out of the image is cut off by the edge of the image. Your brain won't know whether the image is in front or behind the screen any more and you will have strange popping sensations when you look at it.
Disclaimer: This is not a full list of all stereo terms ever. That would be really long, not to mention immensely confusing for people new to the medium.
If you'd like more information, check out one of these links:
3dguy.tv/3d-glossary/
www.stereoscopy.com/isu/glossa…
