Depth of Field and Stereoscopic 3D:

Understanding the effects of Depth of Field and it’s effect on stereoscopic 3d imagery and more importantly the effect it has on audiences minds is something that has not been researched or studied well. DoF is an important tool in 2D Cinematography and in-fact is much coveted as it’s one of the big things that gives a feature Film…it’s “film look”. To explain it briefly, in the picture above the Cat or object B is what is in sharp focus on the camera sensor, or as an analogy, the retina of the eye. The images of the rabbit and the dog do not come into sharp focus and only parts of it are in focus, and rapidly become un-sharp. The “circle of confusion” is thus illustrated in the image above.

When watching such an image in 2D, it helps the Cinematographer or director to direct the attention of the viewer to the area that is in sharpest focus. Try this in a stereoscopic 3D image, and you will create eye-strain in viewers eyes, as the powerful optical illusion that is “3D” forces the brain to send commands to the eyes to try and “fuse” the un-sharp areas. To the brain, a stereoscopic 3D image is after all… similar to the real world.

Trying another 2D Cinematic technique, rack focus… is inviting disaster in a 3D movie if not done really well.

Stereoscopic 3D Coverage of Live Sports thus far:

Two major sporting events amongst the growing many that are lending themselves well to Stereoscopic 3D coverage have been reviewed on this knowledge-base. FIFA 2010 (reviewed here) and the Masters Golf Tournament in 3D here. While the first couple of days reviews have been very critiqued very harshly, given time, most of the issues were ironed out by the crews.

It is our independent opinion that one of the reasons Sports Coverage in 3D is so problematic is due to the cumbersome rigs employed. These rigs may just be the artifacts of Hollywood DoPs being assigned to create the rigs or the fact that rig makers have an un-shakable belief that Beamsplitters with 2 huge cameras are the only way to capture 3D.

In some events such as the FIFA 2010, it may also be the fact that a main sponsor *had* to use their own brand of cameras.

To offer some food for thought on this matter, Consider this:

• In Live Sports, most events take place in broad daylight or in Floodlit arenas as bright as day – So light sensitivity, latitude (f-stops) and sensor (ISO) sensitivity are not that critical, that cameras have to be the huge bulky cinematic ones.
• Live sports are not the same as Narrative Feature films where “Dynamic Range” of the camera sensor and whether it “crushes” blacks and shadows or Blows out intricate highlights such as lamps in an apartment or candlelight flames etc should matter – Another reason why bulky cinema cameras need not be used whereby by default a beamsplitter or mirror-rig is needed so that inter-axial of the lenses can be brought closer.
• Action in a live event is unpredictable. Thus camerapersons need to be able to run along the sidelines with a lightweight 3D camera rig and be capable of smooth motion so as not to cause nausea in audiences

… these are only some of the reasons that a re-look is needed into what comprises todays and future equipment for capture of Live sports n 3D.

All is not lost though. Companies such as 3Ality that are on the cutting edge of Stereoscopic 3D capture are investing huge amount of resources in R&D. Their engineers speak to professionals involved in stereo 3D and are keen to talk to stereographers, so that they can build better tools for this fledging industry.

In 3D, it is our opinion that the right tools be used for the right job. In the case of Stereo 3D capture of sports, Such tools could be rigs based on Si2K minis as the standard for a 3D rig.  The creators of 3D rigs need to look for innovation around them when doing so.

Inside the 3D OB unit:

Currently in an OB van producing a Stereoscopic 3D broadcast for a live sporting event, an overall scenario consists of a camera-person in the field receiving instructions from an online producer regarding camera framing and when they are to get ready to go “live”. Back in the truck, monitoring a bank of preview monitors is a stereographer along-side the online producer (or director or editor). The Stereographer has at his reach a modified controller such as the one pictured below, where the slider can be assigned to change interaxial of the camera pair, and the dial knob can change convergence (usually via toe-ing in the the cameras).

This is an overly simplified explanation,  and in reality the entire “motorized” rig can be controlled to a great extent sometimes semi-automated, such as setting FOV, Zooming and more. Further live “helper” software and hardware can monitor and flag for excessive disparity, vertical mis align of cameras and correct for these in real-time. All these assist the stereographer in order to achieve a workflow that will allow for smooth cutting with correct depth and at the most interesting moments, from camera to camera to make for a compelling live stereo 3D experience. The final switch or “take” is done by the online producer or director.

Making this process more intuitive to the stereographer and the online director is a goal worth striving for, the benefit of which will be eye strain free 3D experiences for the audiences. With that in mind lets look as some food-for-thought for creating some innovations in Live 3D capture for Sporting events.

The Circle of Isolation; Creative usage of DoF for Stereoscopic 3D:

Similar to ‘circle of confusion’ which was explained at the beginning of this article, and as we are talking about stereo 3D, let’s define some new terminology and call it “Circle of Isolation”.

Looking at the picture above (click for larger) it is clear that the best 3D would arise from the image on the right, where the area of interest is in sharp focus and, with proper framing, would hopefully give nice “rounded 3D” while the background is completely blurred and thus the brain would adapt, exclude, and not force the eyes to fuse the background imagery.

On the image on the left it can be seen how the eyes could get distracted and try to un-successfully fuse the out of focus imagery.

In live sports, being able to selectively Isolate a player or person of interest, can make for some very creative stereoscopic 3D, and would be similar to the 2D version but without the side effects of semi blurred surround imagery that may lead to eye-strain and headaches over the course of a watching an event in 3D.

So… how could this Circle of Isolation be achieved?

Sony’s NEX-5 Digital SLR  camera has a unique feature, which allows you to “dial in” the amount of de-focus for the background, once you frame the subject of interest. Taking a cue from the technology that does this in their camera,iIt would be innovative and intuitive to put a “track” and “isolate” button on the wireless controller… This could be implemented in parts:

1. A simple isolate..where the stereographer chooses the target “player” or “coach” or object to drive people’s attention to. The motors drive focus on this subject, send the lens metadata to SIP 2100, and then if red-flagged for too much disparity, it automatically converges the cameras. by opening the lens arpetures (usually most sports are in broad daylight or floodlit so a good lens and sensor should be able to give nice fat DoF)
2. Autofocus apparatus tracks the chosen subject for isolation, and a steep blur is attached via a customized version of realtime stereo processing hardware such as the SIP 2100 to any pixels that are not in a threshold of sharp focus.

The reasoning behind this thinking, is that even though Depth of Field is an enemy of 3D; (rack focus for example), if it is applied creatively, it can be used to create extremely good stereoscopic experiences.

This effect may not work with exteme zooms, but with mild to moderate zooms it could still give “rounded 3D” on the subject of interest, and yet Blur the entire background so that people don’t try to fuse non sharp areas that lead to eye-strain. In the soccer image on the right below (click for larger): There is good Isolation.. the background is blurred well.

In the same image on the left above, It would be bad if it had been shot in 3D. People might try to “fuse” player 19 because he could be a superstar etc.. and fail to do so because he is not in clear focus, resulting in eye-strain and a headache.

For such a shot it would make sense to have infinite focus and infinite Dof (f11 or f22). – or – “isolate” player 12. Obviously knowing when to apply an “isolate” is important.. and needs quick thinking during a live game, so may not be applicable in a “tackle” shot as in the scene above.

Some further food-for-thought for Live Sports coverage in 3D…

Gyro Stabilized Hand Held 3D Rig:

The use of Gyro Stabilizers to allow a compact Si2K mini rig that can be hand-held and will allow the cameraperson to run along the sidelines of a play-field or basketball court, while achieving smooth Steadicam like motion.

The image above without the mattebox, and with a pair of Si2K minis, would make a compact side-by-side 3D rig that would allow an operator to “Dolly” in close by running up to the action instead of Zooming in and risking flat card-board like 3D coverage of the sporting event.

Compare this image to the image of the previous 3D rig in the article, and you begin to see the need for innovative thinking for live 3D. The Si2K Minis allow a portable laptop to be carried in a backpack if recording is needed, but as this is a Live event, a Gigabit Ethernet cable should suffice to a base-camp. As this is a food-for-thought article, we have not fully investigated the distance of mobility that will be afforded when tethered to the cable. At any rate an HDSDI 3D signal could go out directly from a backpack worn by an operator and containing a portable battery, Laptop and HSDI module. R&D is strongly encouraged.

Above: a side by side Iconix camera based 3D rig from 3Ality.

Yet another solution is the ingenious POLECAM and Polecam 3D (article in german), when coupled with an Iconix machine vision camera solution for Stereoscopic 3D.

Disclaimer: The article above contains many forward thinking statements and is written as creative fodder for those interested in furthering and refining the state of the art in coverage of Live events in stereo 3D. All copyrights of images, companies and products mentioned, are acknowledged as belonging to their respective owners.