3d subjective testing

3D SUBJECTIVE TESTING

Juan Reyes [email protected]

July April 201110

mailto:[email protected]

BluFocus – White Paper – 3D Subjective Testing Page 1 Page 1

Table of Contents

INTRODUCTION ................................................................................................ 2

PURPOSE ........................................................................................................ 2

DOCUMENT STRUCTURE ..................................................................................... 2

ISSUE TERMINOLOGY ...................................................................................... 2

IMAGE EXAMPLES AND DESCRIPTIONS ................................................................ 2

3D Issues ..................................................................................................... 3

GHOSTING (CROSS-TALK) ................................................................................. 4

CARDBOARDING ............................................................................................ 5

EXTREME DIVERGENCE .................................................................................... 6

EXTREME NEGATIVE PARALLAX ......................................................................... 7

HYPOSTEREO OR ‘GIANTISM’............................................................................ 8

HYPERSTEREO OR ‘LILLIPUTISM’ ........................................................................ 9

EDGE VIOLATION ......................................................................................... 10

VIEW DISCREPANCY ..................................................................................... 11

MULTIPLE POINTS OF REFERENCE .................................................................... 12

ABRUPT DEPTH CHANGES (ESPECIALLY BETWEEN SCENE CUTS) ............................... 13

REVERSE/PSEUDO 3D .................................................................................. 14

OBJECT EDGE PLANE DISTORTION ................................................................... 15

FALSE DEPTH .............................................................................................. 16

FOCUS VARIATION BETWEEN VIEWS ................................................................ 17

IMAGE VARIATION BETWEEN VIEWS ................................................................ 18

DEPTH CONFLICT ......................................................................................... 19

CONCLUSION ................................................................................................. 20

CONTACT US ................................................................................................. 21


INTRODUCTION 3D is an art form as well as a science. Creating 3D content requires a lot of vision and creativity, but with awareness and consideration for the technical aspects of it. Whether the 3D content is created through the use of 3D cameras and 3D shooting techniques, or through a 2D-to-3D conversion, the technical and physiological aspects need to be considered. It is very easy for technical issues to exist in 3D material that may possibly result in an unpleasant experience for the viewer. With the 3D technology now making its way into the home, it is very important – for the technology and for the industry – that the quality of the 3D content that the viewers are watching from their homes is the best possible quality. The early adopters of 3D in the home will view it and they will tell their friends, they will show their friends, they will post their experiences on social networks, etc. It is important that these early adopters receive the best possible 3D experience. It is the responsibility of the industry to ensure that the 3D content delivered during these early stages and beyond is of the highest possible quality so that it can continue to be adopted by consumers. For this reason, we must understand how to properly test 3D content and know what to look for.

PURPOSE The purpose of this white paper is to describe some of the more common issues that can exist in 3D material. Providing the terminology and examples throughout the document will assist in finding and avoiding issues. Although many of the issues that may exist in 3D content are inherent to the source, it is important that the issues are understood and communicated to the appropriate groups or individuals. The appropriate groups or individuals can then determine whether adjustments and corrections need to be made.

DOCUMENT STRUCTURE The issues described in this document are listed with a significant amount of detail to help make them as easy to understand as possible. The information included with each issue includes the following:

ISSUE TERMINOLOGY Being able to properly understand, define and describe issues is an extremely important aspect when communicating with the content owners, producers and others involved throughout the creation and delivery workflows that will deliver 3D content to the home. Several common terms that describe issues are listed in this white paper in order to provide a common language and understanding of 3D issues that can occur.

IMAGE EXAMPLES AND DESCRIPTIONS For each issue, an image is provided to serve as an example of how the issue may appear to the user. A description of how each issue would appear is also included to further clarify the sample image. In some cases, possible causes of the issue may be included.


3D Issues


GHOSTING (CROSSTALK) This occurs when the image that is destined for one eye is visible to the other eye. The result is that the viewer will see a double image. This is most commonly referred to as ghosting or crosstalk. In more severe cases where ghosting is occurring in both eyes, a triple image may be seen. When this occurs, the ghosted image is seen as a semi-transparent image adjacent to the main image. A diagram demonstrating ghosting is shown below in Figure 1:

Figure 1

In Figure 1, the image in the center should be visible to the viewer with the desired amount of depth. However, in this case, the viewer is seeing a blurry image due to the fact that he the viewer is seeing three instances of it. As a result, the viewer has difficulty focusing on the object and it distracts from the rest of the details in the scene. It is possible for this issue to be a result of the equipment used rather than the content. It is therefore recommended that the content be tested using different types and/or brands of equipment.


CARDBOARDING

This is a phenomenon where the objects on the screen appear to be very flat and havewith little to no depth. There may be multiple planes visible to the viewer, but each object in each plane is very flat as if it were a cardboard cutout. An example is demonstrated below:

Figure 2

Figure 2 represents the front view of the screen where three separate images appear. Each image sits on a different plane with a different depth. However, the viewer sees each image as an almost flat image with virtually no depth.

Figure 3

Figure 3 is a top-view representation of what the viewer is seeing. Note that each of the three objects has the appearance of being flat and not having any much depth.

Figure 4

Figure 4 represents what the desired appearance should be. Here, each object is displayed with the appropriate amount of depth, resulting in a more realistic viewing experience.


EXTREME DIVERGENCE

Divergence is described as the ability to move both eyes so that they turn outward together. For 3D viewing, if an object has a significant amount of positive parallax, causing the divergence between the left-eye and right-eye image to be extreme, it may cause the viewer to move his or her eyes outward more than normal, making it difficult or impossible to focus on the object. This is especially significant with children, as their eyes are closer together. This often results in eye strain and/or an uncomfortable viewing experience. An example is demonstrated below:

Figure 5

Figure 5 represents an object with some divergence required to view.

Figure 6

Figure 6 represents an object where the separation between views requires a significant amount of divergence from the viewer, making the object difficult or impossible to focus on.


EXTREME NEGATIVE PARALLAX

When the depth of an object places it in front of the screen plane, it has negative parallax. If the depth of the object contains an extreme amount of negative parallax that places it significantly in front of the screen plane, it can require the viewer to converge his or her eyes to a point at which it is difficult or impossible to focus on the affected object. This is especially significant with children, as their eyes are closer together. This often results in eye strain and/or an uncomfortable viewing experience. An example is demonstrated below:

Figure 7

Figure 7 represents an object with slight negative parallax requiring some convergence required to view.

Figure 8

Figure 8 represents an object where the separation between the views requires a significant amount of convergence from the viewer, making the object difficult or impossible to focus on.


HYPOSTEREO OR ‘GIANTISM’ When the left-eye and right-eye separationdepth applied to an object makes that object seem larger than normal, the affected object may appear to be out of proportion with a scene. This may result in the viewer sensing that the scene is appears unnatural. An example is demonstrated below:

Figure 9

Figure 9 represents a scene with all objects proportionally displayed.

Figure 10

Figure 10 represents a scene in which the stereo separationdepth of on the mailbox causes it to appear larger than life and out of proportion.


HYPERSTEREO OR ‘LILLIPUTISM’ When the left-eye and right-eye separationdepth applied to an object makes that object seem smaller than it should, the affected object may appear to be out of proportion with a scene. This may result in the viewer feeling that the scene is unnatural. An example is demonstrated below:

Figure 11

Figure 11 represents a scene with all objects proportionally displayed.

Figure 12

Figure 12 represents a scene where the stereo separation ondepth of the house causes it to appear very small and out of proportion.


EDGE VIOLATION

Objects that contain a significant level of detail that extends beyond the edges of the screen can create focus issues, as the view for one eye may not have all the same detail as the view for the other eye. This can result in an uncomfortable or distracting viewing experience when the viewer attempts to focus on the object or objects with affected by thethis edge violation. An example is demonstrated below:

Figure 13

Figure 13 represents a scene in which the two objects near the left edge of the screen contain edge detail that may be difficult for the viewer to focus on. This is because some of the detail needed for the viewer to focus on the object is not present as it extends beyond the edge of the screen for one of the eyes.


VIEW DISCREPANCY This occurs when there is information for one eye that is not included for the other eye. This can result in the affected object appearing to be slightly transparent and/or showing an incorrect depth. It commonly occurs with reflections. An example is demonstrated below:

Figure 14

Figure 14 represents a scene where a reflection is captured by the camera that is shooting for the right eye but the camera that is shooting for the left eye is not capturing the reflection. This is often the result of the different positions and/or angles between the two camera lenses when capturing the material. The angle from one lens of the camera may capture the reflection while the angle from the other lens may not capture the reflection. The viewer in this example may see the reflection as being slightly transparent and/or appear at a different depth from the object creating the reflection.


MULTIPLE POINTS OF REFERENCE

This occurs when additional objects, such as titles, burned-in text, menu buttons, sport scores, statistics, etc., are visible on the screen and the stereo separation or focal pointdepth of the additional objects does not correspond with the depth of the video content that is currently is playing. This can become very disruptive as ie. It requires the viewer to select which object he wishes to focus on and view (i.e. title, credits, buttons, etc.) as it is not possible to focus on both the video and the additional objects because they have different applied depths. An example is demonstrated below:

Figure 15

Figure 15 represents a scene in which the mailbox is the focal point of the scene. However, a title treatment added in post-production is at a very different depth than the mailbox. In addition to this, menu buttons appear on the screen, that which are also set to a different depth that than the depththose of the mailbox and the title treatment. The result here is that there are three unique focal points with different depths that the viewer would need to focus on independently, making the entire scene somewhat distracting.


ABRUPT DEPTH CHANGES (ESPECIALLY BETWEEN SCENE CUTS)

When there are abrupt scene changes and the depth change between scenes is significant, the result may be an abrupt and uncomfortable viewing experience to the viewer. This occurs because the viewer’s eyes must quickly converge or diverge from one scene to the next in order to properly focus on the point of focus. An example is demonstrated below:

Figure 16

Figure 16 represents a scene in which all objects are displayed with a specific depth with positive parallax. After this scene, a cut takes the viewer immediately to the screen shown below in Figure 17.

Figure 17

Figure 17 represents the next scene, where there is negative parallax that requires the viewer to quickly adjust his eyes so he can focus on the scene. This may be uncomfortable for some viewers.


REVERSE/PSEUDO 3D

When the left eye and right eye are reversed, the result is an untrue overall incorrect depth. This can occur when the left and right files are reversed in various stages during the production process. It is most noticeable when a scene is paused. You will see items in the background that should be in the foreground and vice versa. An example is demonstrated below:

Figure 18

Figure 18 represents a scene which, to the viewer, appears to have depth. However, although the trees seem to be physically located behind the house and the mailbox seems to be physically located in front of the house, the viewer will get a sense that although there is depth in the scene, it seems incorrect or unnatural. The reason for this is further clarified below in Figure 19.But there is a sense that it seems unnatural.

Figure 19

Figure 19 is a top view representation that demonstrates the perceived depth which is the result of having the information for the left eye and right eye reversed. The result is that the objects that should appear closer actually appear further away and vice versa. It is helpful to “pause” the scene in question when looking for this type of issue, as it stops all action and movement.

Formatted: Font: Bold

Comment [K1]: Are the labels on Fig 18 correct? To me, it doesn’t look like the trees are in front of the house and the mailbox is behind the house.


OBJECT EDGE PLANE DISTORTION

This occurs when the edges of an object appear to reside on a different depth plane than the rest of the object. It is found more frequently in 2D-to-3D conversions. It appears as if the affected edge of an object appears on a plane in front of or behind the object of which it is a part. An example is demonstrated below:

Figure 20

Figure 20 demonstrates an object where the top of the head appears to the user as if it sits on a depth plane behind the rest of the head.

Figure 21

Figure 21 demonstrates how the top of the head does, in fact, seem appear to reside on a different depth plane than the rest of the head.


FALSE DEPTH

This occurs when the depth of an object or part of an object appears in a manner that seems unnatural. This is found more frequently in 2D-to-3D conversions. It appears as if a part of an object exists on a different plane than the rest of the object. An example is demonstrated below:

Figure 22

Figure 22 demonstrates an object (in this case, the reflection), which, to the viewer, seems to appear in front of the cylinder instead of on it.

Figure 23

Figure 23 provides a top view representation of how the reflection does in fact seem to appear in front of the cylinder instead of on the same plane.


FOCUS VARIATION BETWEEN VIEWS

This occurs when the focus on left and right lenses are not set the same. This can result in the overall image appearing out of focus. An example is demonstrated below:

Figure 24

Figure 24 demonstrates how the image captured for the right eye is in focus but the image captured for the left eye is slightly out of focus. The result is the overall scene being out of focus.


IMAGE VARIATION BETWEEN VIEWS

This occurs when some of the image details vary in each view. These differences can include color, brightness and other details. It also can include compression artifacts between views. This can result in a degradation of the image quality for the affected area and/or cause the affected area to be difficult to focus on. An example is demonstrated below:

Figure 25

Figure 25 demonstrates how the image for the left eye contains color and brightness differences from the image for the right eye. It also contains compression artifacts in the right eye that do not exist in the image for the left eye. The result would be that the overall scene may appear blurry and/or difficult to focus on.


DEPTH CONFLICT

When an object, such as a title treatment, physically resides in front of an object, but the depth or parallax applied to it places it behind the object, a depth conflict occurs. This appears as the object physically in the foreground incorrectly cutting through the object physically residing in the background. An example is demonstrated below:

Figure 26

Figure 26 represents a scene where a title treatment was added in post-production. The text is physically in front of or on top of the all objects in the scene. However, the title treatment has positive parallax, placing it on a depth plane behind the house and trees as demonstrated in the top view example in Figure 27.

Figure 27

Figure 27 is a top view representation that demonstrates the depth of the title treatment. The depth of the title treatment places it behind the house and trees, causing it to appear to incorrectly cut through the house and trees.


CONCLUSION

Accurate testing of 3D material is extremely important. Creating the 3D experience for the viewer takes a tremendous amount of planning and creativity. Even with all of the planning and attention to both the creative and technical details, issues still can exist that could affect the 3D experience for the viewer. It is important to accurately search for these types of issues. Avoiding and correcting these issues as much as possible will result in a better 3D viewing experience and in the long run, more adoption of the 3D technology in the homes of consumers.


CONTACT US

JUAN REYES CHIEF TECHNOLOGY OFFICER [email protected]

PAULETTE PANTOJA FOUNDER/CEO [email protected]

BLUFOCUS INC. 10911 RIVERSIDE DRIVE SUITE 200 NORTH HOLLYWOOD, CA 91602 USA 818-294-7605 WWW.BLUFOCUS.COM



3d subjective testing

Technology