(ACB) 'Anaglyphic Contrast Balance' is an embodiment of New Zealand Patent 505513 and U'K' Patent 2366114 and Australian Patent 785021 + Canadian Patent 2352272.

Convert HD 3-D into Anaglyph with the (ACB) 3-D Action Set.

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Make Still or Motion Anaglyphs with the (ACB) 3-D Action Set.

(ACB) 'Anaglyphic Contrast Balance' is an embodiment of New Zealand Patent 505513 and U'K' Patent 2366114 and Australian Patent 785021 + Canadian Patent 2352272.

Camera base separation of 1/30th the distance from the nearest object is common advice. This stems from purpose built 3-D film cameras having 65mm lens separation, 1/30th of the 2 metre wide screen used for polarised slide display. Film camera views overlap at approximately 2 meters wide, 2 meters away. So lens separation of 1/30th the distance from the nearest object applies for intended screen display of up to 2 metres wide.
With two separate cameras, you have an opportunity to adjust the lens base separation to suit the scene. Unlike 2-D screen image, 3-D images have a built in maximum screen size that is limited by the disparity of the views. In an anaglyph image the disparity is demonstrated with the color fringes around objects. When the disparity is wider than your eye spacing, it becomes difficult if not impossible to view.
Consider that you intend to display 3-D on a 2 meter wide screen that will be ideally viewed from 4 meters away.
The most realistic you can make the 3-D image appear is by filming with the cameras separated at your eye spacing, 62.5mm, converging the cameras at 4 meters away, by zoom or lens angle, to 2 meters wide at that distance. This creates an orthoscopic 3-D screen image with realistic image size and parallax 1:1 in scale viewed from 4 meters away on a 2 meter wide screen. Infinity, the very distant horizon, will have your eyes viewing parallel as in natural viewing.
The image as described above will also look fine on screens smaller than 2 meters. But it will no longer be orthostereoscopic. Footage intended for small screens need not maintain a parallel eyes view of infinity in order to avoid the image disparity from overwhealming the small screen width.
But if the above image is displayed on a screen twice as wide, the disparity also doubles and your eyes will then have to diverge wider than parallel to see the the image background. The closer you are to the screen the more your eyes will be required to diverge. Viewing from further back will help narrow the viewing angle. You may get away with a little bit of excess separation, but not double, especially for novice viewers. To assist, when projecting the image, converging the projectors will reduce the background disparity, but at the expense of having the foreground float in front of the screen. The floating screen effect is usefull for cinema size screen projection.
If you zoom in on 1 Meter wide views of your scene, ie half your intended orthoscopic screen size from 4 Meters back, the image size will be doubled on your 2 meter screen. So will the disparity, making the image unviewable. So reduce the lens separation to half of your eye spacing to maintain an orthoscopic view. If you cannot get the cameras closer together in order to half their separation, then zoom in from 8 Meters back in order to half the parallax to maintain viewability. The zoom will flatten the stereo perspective and so the image will not be orthostereoscopic, but it will be viewable with the same parallel eyes view for infinity.
If you zoom out to 3 Metre wide views, 1.5 times wider than your intended screen, you may then make the camera separation up to 1.5 times your eye spacing. Or it will look fine left as is.
With reference to the intended screen width and ideal viewing distance, reduce the lense separation proportionaly when filming from closer and increase lense separation proportionaly when filming from further back. If you film from 2 Meters away with wide angles converged at 2 Meters wide, it will cause the ideall screen viewing distance to be 2 Meters from the screen. The view from further back will look fine but will appear stretched, accentuated, and not quite as realistic. So reduce lense separation by half for your viewers sitting at four meters.
Keeping well within these guidelines will help ensure a consistent viewability and perception of image depth. However, filming up to this guideline will sooner or later lead to unviewable footage for your screen size. So aim to undershoot the camera separation especially when you have a large screen size in mind.
If the camera base is too large it will not help the 3-D effect, it will reduce the potential screen display size.

Having parallel left and right views for the capture of a stereo pair is common advice. But this only applies when the stereo pair is produced on film inside the cameras. However, converged camera views have the advantage for full screen display where image height difference between the views can be equalised.
With natural stereo vision we converge our eyes lines of sight to focus on objects nearby and we progressively diverge our lines of sight to focus on objects that are further away. When looking to the distant horizon our lines of sight are virtually parallel.
In natural vision when we gaze about, everything we choose to look at is imaged correctly in 3-D as the convergence and focus of our eyes adjust in unison to suit the subject of central attention being looked at. Objects outside of our center of converged viewing are double imaged and out of focus and are perceived with less detail.
When taking a stereo photo with the camera's lenses converged to meet with the subject of interest, as with natural vision, only the area of central convergence is presented correctly. The heights of objects that are outside of the central area converged upon in the left and right views are different. Object image size on the right side of the left image is smaller than the corresponding right side of the right image, and visa versa. This is referred to as keystoning.
For film projection of converged views the keystoning effect may be compensated for by converging the left and right projectors to reverse the keystone effect on screen. But this is only effective where the degree of camera convergence in the image capture was fixed and constant.
Any vertical height difference in the stereo pair hinders the viewability of the 3-D image. Everything in the stereo image should be presented as viewable at the discretion of the observer. The vertical height of all points common to the left and right images must be equal, as if converged on in the original scene.

Parallel 3-D imaging is best for stereo prints and slides where there is no further opportunity to correct the image height of the stereo pair. But parallel imaging does not completely correct height difference and it results in a loss of frame width.
When making a stereo pair intended for viewing directly from film in a slide viewer or by projection, it is preferred that the two camera views are parallel and aiming straight ahead. This assists with reducing vertical height difference that results from convergence. The left side of the left image and the right side of the right image are then masked or cut off as the details they show are not common to the other image.
Height imbalance still remains due to the difference in distance between the subject and the two lenses. Objects on the sides of an image scene are closer to one lens than to the other resulting in different image sizes. This is less apparent when objects are further from the camera. This effect also occurs with natural vision as a secondary cue for the location of objects.
Another factor is that the focal length of the lenses in a stereo camera are not exactly matched. One lens will provide a slightly wider angle of view resulting in a smaller image size.
Parallel imaging results in an a loss of full frame width to an aspect ratio not suitable for full screen display. Further cropping to re-establish aspect ratio reduces the image resolution.

A converged stereo pair can maintain full frame width and be height adjusted to equalise the left/right image height. This enables the entire image to be correctly observed.
Digitised converged stereo pairs, can be height equalised by adjusting the stereo pair after image capture. A preset bias of a stereo cameras' CCD's can also achieve this. To the (ACB) 3-D Image Gallery. 3-D Photography by Marc Dawson.
As parallel camera views require image height correction anyhow and result in a loss of frame width, the convergence of camera views is then preferable as it enables full frame width to be maintained. Correction of converged camera views is STUDIO 555's preferred method for still or motion stereo pair capture and for the presentation of printed, screen projected or monitor displayed 3-D images.
See examples of converged height equalised 3-D images in the STUDIO 555 (ACB) 3-D ANAGLYPH GALLERY

For Still and Motion Stereoscopic Photography and for Alignment of your Stereo Pairs, Contact  STUDIO 555

Anaglyphic Contrast Balance (ACB) 3-D is an embodiment of New Zealand Patent 505513 + U'K' Patent GB2366114 + Australian Patent 785021 + Canaian Patent 2352272.

Anaglyphic Viewing

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