English English
German flag

What are good 3D photos?

Bild 1

In the following article you will be shown by pictures, which technical properties good 3D images have and which errors occur again and again, which make them unattractive. Stereoscopic 3D images are the most intense in their perception. If these are correctly implemented, a well-being is triggered. If 3D images are poorly implemented, they will be uncomfortable, even if the motif is attractive from a monoscopic point of view.


What are good 3D photos? In simple words: Good 3D photos are more pleasant than normal photos, because they give the viewer the opportunity to look into the distance. So if you do not get tired when watching a 3D photo for a long time, then you've done everything right in production. Stereoscopy is not primarily about creating a 3D effect, it is about a realistic room conception.

In detail, good 3D photos have the following technical characteristics:

  1. The shooting angle of both cameras is set so that the result of a 3D photo, a deviation between 1/20 and 1/40 of the overall picture results.
  2. The perspective image of the vanishing point corresponds to human vision.
  3. In the framing, no objects and surfaces break through the edge of the picture.
  4. The assembly fixes height errors and horizontal alignment.
  5. Except for the viewing angle, the image pair is absolutely identical, so that no synchronization errors and no flickering are perceived.
  6. Extreme popup effects (negative disparity) does not have the 3D photo.

Conclusion: Only when all the technical features of a 3D image are properly implemented, only then has the motif itself a correspondence.

Before we go into detail on the individual technical properties, there is a short statement that describes the importance of stereoscopy.

 

Stereoscopy is like music for the eyes

Art satisfies the senses of man. For our sense of hearing it is the melodious music, for our sense of sight it is the beautiful pictures. When music is played on poorly tuned instruments and it is also sung wrongly, it is cruel for the listener to continue listening, even if it is a cover song that is actually popular. In monoscopic images, it is not so bad. Ugly pictures have little agreement from the viewer, but the eyes would not hurt. Stereoscopic images are different. If an image is displayed for each eye, which corresponds to the technical requirements of 3D images, then a depth effect is simulated which gives the viewer the feeling of being in the middle of the image. If the 3D image is flawless, it triggers a positive emotion for the viewer. Smallest errors in the technical implementation and presentation of 3D images are immediately noticeable to everyone and big errors can also cause pain to the eyes. Therefore, it is essential to follow the technical characteristics for good 3D photos.

 

Note to the following photo series

The following photo series shows a virtual room by metric units. The technical details on the left lead to the same result as in the real world. It also shows images that are imperfect to visually demonstrate how not to do it.

 

1. The deviation

The shooting angle of both cameras is set so that the result of a 3D photo, a deviation between 1/20 and 1/40 of the overall picture results.

This means that should not be too high, the depth of a stereoscopic image and not too flat. Deviation is the distance between two images that together form a 3D image. In anaglyph images you can see the deviation to the red and blue image offset which should be displayed in the correct ratio.

Bild 1

Everything is done right here. With a base of 6.5 cm, which corresponds to the human eye distance and a natural vergence of 0.75 degrees, a deviation of 1/30 of the total image results, which is the best compromise for all media. If the main subject (the woman in the middle of the picture) is directly behind the zero level, then one would fully exploit the depth effect. Good 3D images show the depth of a space that is best seen when there is something immediately nearby.


If the deviation is too broad, then the depth effect is too high, which can be unpleasant for the viewer.

Bild 2

At too high a Vergence results in too wide a deviation, even if the base still corresponds to the human eye distance. In the assembly, you can fix the problem, if the main subject in this case is not closer than 2.5 m away.

Bild 3

At first glance, the picture seems to be in order. However, because too much vergence has been selected in the original recording and this has only been corrected during assembly by moving the image pair, fatigue phenomena only appear after a few minutes. Therefore, it is important to choose the correct vergence between 0.5 - 1.0 degrees right from the beginning.


The most common mistake with a bad deviation is to get too close to the main motive. The main motive is then before the zero level and breaks through the edge of the picture.

Bild 4

In such cases, the image is often remounted to better represent the main subject. However, the deviation of the background increases into the unbearable.

Bild 5

The deviation distance should not be wider than 1/20 of the overall picture. Therefore, such pictures are unfortunately no longer to save - not even in the post!

In order to take close-ups, one should reduce the base in order to achieve a balanced deviation again.

Bild 6

If you can not reach a base of less than 6.5 cm for technical reasons, you can also take a close-up with one camera. It is important that the motive does not move in itself.

Anyone who still wants to make a close-up with a base of 6.5 cm, could still achieve a result with a strong telephoto lens and a high distance to the main subject, so that the eyes do not hurt so much.

Bild 7

However, the vanishing point is very unnatural and the main theme is very flat. Such images can just be allowed under an artistic aspect, but it has nothing to do with the natural human visual behavior.


If you take pictures of a supertotal with a base of 6.5 cm, then the picture appears very flat and pulled back. With this basis, even at 20 meters distance to the subject no depth effect can be seen.

Bild 8

In a supertotale the hypestereo method is recommended, which is recorded with a high base, so that the depth effect can be fully exploited.

Bild 9

If you do not want to hyperstate in a supertotal, you should at least make sure that there is something nearby so that a 3D image has its equivalent.


A natural deviation is determined by the shooting angle (vergence) of both cameras. If both cameras were exactly parallel to each other then the farthest point in the subject would be the zero level. The whole picture would come out of the screen.

Bild 10

In the assembly, you can fix the problem, if the main subject is not closer than 2.5 m away. The right and the left image is pushed together accordingly until an artificial zero level is created and a depth effect can be seen again.

Bild 11

Again, the picture seems to be fine at first glance. However, because no vergence has been set in the original recording and this was simulated only during assembly by moving the image pair, fatigue phenomena occur only after a few minutes. Therefore, it is important to choose the correct vergence between 0.5 - 1.0 degrees right from the beginning.

The correct deviation is also dependent on the size of the overall picture in the presentation. Which deviation is suitable for which medium is illustrated in the following article in detail.

To Article

 

2. The vanishing point

The perspective image of the vanishing point corresponds to human vision.

This means that the vanishing point, as we perceive it in nature with our own eyes, to be displayed. Wide-angle lenses distort the image, which in the long run is unpleasant for the viewer. Only wide-angle images with a directory correction, so that all lines are straight, can still be considered under an artistic aspect, but it has nothing to do with the natural human visual behavior. Bent frog eye images would not work, because it comes to the edges of the image to unpleasant disturbances. The right lens with a full-format sensor would be 50mm.

Bild 12

Wide-angle images up to 180 degrees are only used with VR glasses, because here the viewer perceives only one image detail at a time. Only with your own head movement you can capture the entire picture.

 

3. The framing

In the framing, no objects and surfaces break through the edge of the picture.

This means that if picture elements should protrude from the screen, then they should at best not break the edge of the picture. It just looks unnatural when outstanding picture elements are cut off the edge of the picture.

Bild 13

For minor frame errors, you can easily improve the picture by moving the picture if it does not make the deviation too wide.

Bild 14

So if you shoot with a base of 6.5 cm, you should always make sure that nothing is closer than 2.5 m in front of the camera. If you are not sure, then it is useful to have a tape measure with you.

In large screen projection as in the cinema, the framing rule does not apply because the viewer is several meters from the screen. The 3D perception is already largely lost at 6 meters distance to the main subject. Therefore, the deviation in the far field in large-screen projection is set to almost zero, thus bringing the 3D image closer to the viewer. The calibration of the deviation must therefore be set in relation to the size of the image projection and the distance of the viewer to the image projection in order to produce an optimal 3D experience.

Even in the anaglyphic printing process, pixels may break the edge of the screen slightly to avoid ghosting effects.

In general, if the playback technology can not cleanly separate the stereoscopic image for each eye, so that you keep taking ghosting effects, especially inferior 3D TVs or autostereoscopic monitors, then it is better to mount the image forward and to slightly ignore the rule of framing. A clean overall picture is more important than errors on the edge of the screen.

 

4. The assembly

The assembly fixes height errors and horizontal alignment..

This means that the stereo image pair in vertical alignment exactly matches a horizontal line. For our eyes, it is not possible to see the right eye up and the left eye down. The slightest deviation in the image height can be very unpleasant to the viewer. Therefore, it is very important to be very careful in the installation of height correction.

Bild 15

Oblique images are unsuitable in stereoscopy because we hold the head in a horizontal axis. It is unreasonable that the viewer has to angle his head to see the picture in good quality.

Bild 16

 

5. flickering pictures

Except for the viewing angle, the image pair is absolutely identical, so that no synchronization errors and no flickering are perceived.

This means it is absolutely essential that both cameras must have the same settings for image recording. All automatic programs of cameras do not always work reliably. Therefore it is better to take pictures in manual mode. The slightest deviation can cause a picture flicker. The color temperature must match as well. Be especially careful with highly reflective and shiny surfaces because here already low vergence represent the reflections different. If you make a hyper-stereo or macro recording with one camera, you should definitely correct sync errors in post-processing. Picture flickering is very uncomfortable for the viewer.

Bild 17

In this picture you can see a clear image flicker on the head and hand. Such problems arise when you do not photographed synchronously and the subject is moving.

 

6. negative disparity

Extreme popup effects (negative disparity) does not have the 3D photo.

This means that when picture elements are floating in front of the zero level, the impression arises that something sticks out of the screen. If you were to exaggerate with this effect then it would seem to the viewer as if the object was right in front of your nose. Focusing the eyes on something very close is very exhausting. Therefore, it is important to deal only discreetly with negative disparity. The maximum width of the deviation in the near range should not exceed 1/40 of the total picture.

Bild 17

The model helicopter is shown here in the picture too close.

A bit further back, so just before zero level then the picture is more pleasant to look at.

Bild 19

 

Are these rules synonymous for 3D movie production?

Yes. All 6 rules of stereoscopy also apply to 3D movie production. Furthermore, there are other rules for 3D movie production to make it a pleasant viewing experience for the viewer.

  1. No hectic and shaky shots - not even with action scenes. Each camera movement is nothing more than a head movement for the viewer.
  2. No too fast cuts. Cuts under two seconds is very troublesome for the viewer in the long run.

Fast camera shots and cuts have their equivalent only in monoscopic films. If you want to produce a 3D movie, you should plan it right from the start. In steroscopy, other standards apply in the scene. Therefore, it is not recommended to convert a monoscopic movie into 3D.