Interaxial Distance

"Sometimes, looking at the loss of funds on our balance sheet, I really feel that agreeing so easily to shoot such a big-budget movie was perhaps a mistake.

Standing on the set, looking at the equipment in front of the crew, Alexander, one of the producers of this film, took a long time before slowly speaking.

It has been a while since the preparation and investment for the Three-Body Problem 2 movie began, and now it's June. The preparations for the movie are also in full swing. Equipment is in place, models are set up, scenes are arranged, and the crew's preparations are further perfected.

Some say that watching one's efforts in business take shape before one's eyes is a joyful thing. However, Alexander, looking at the construction of the crew, couldn't feel any joy. 

Looking at these things, all he could feel was that they were burning money. He knows the cost of each item very well, but he can't find any sense of accomplishment.

"Maybe you're right. My business is actually about making money. You all seem happy watching the construction of the crew, but I always feel heartbroken. And looking at the box office, you all don't have much reaction, but I'm especially excited. Maybe our careers are indeed different; I am more focused on money..."

Alexander mumbled and opened his mouth again but said a lot without hearing Levi's response. When he turned around, he found Levi no longer beside him. Now, he stood by the bracket-mounted camera, manipulating the machine.

"Nick, I'm talking to you," Alexander said somewhat angrily.

"All you're saying is how much money the movie cost. You've been talking about it every day these days. Don't you find it annoying? I'm getting tired of it," Levi waved his hand. "Believe me, the money spent will definitely be recouped."

"You say it's easy because you don't even know how much money was spent," Alexander retorted.

Looking at the bracket-mounted camera next to Levi, Alexander immediately had this thought. For example, this camera costs a lot of money.

Shooting a 3D movie requires the use of a dual-lens bracket-mounted camera, and the investment in such a camera is substantial. The accompanying lenses are also an expense, and this camera is heavier. When it comes to showing different shots, how to move it is another problem. The film costs of the two cameras, that's also money... In his eyes, all these things are money.

But Levi doesn't seem to care much about these things.

"I don't know how much was spent, but as long as it's earned back, isn't it settled?" But Levi didn't express anything about it. He just waved his hand.

"It's not that easy," Alexander mumbled again.

"I know it's not easy, but because it's not easy, it's more meaningful to strive, isn't it? We're all working hard; why keep complaining?" Levi straightened up, turned his head, and spoke to Alexander. His words left Alexander somewhat speechless for a while.

For Levi's optimistic attitude, Alexander was somewhat helpless. However, he also knew another thing very well: what he paid might be just some money for this movie. But what Levi paid was much more hard work than him.

Since the preparation of the movie began, Levi has been immersed in the crew, which Alexander is very aware of. He knows that if there's something troublesome about this movie, it's definitely not the investment but the technology.

Not all movies can immediately start shooting 3D movies with a 3D camera. 3D movies and 2D movies have many differences in shooting methods; they are two completely different things. 

Before, no one had shot a 3D movie, so how to shoot such a movie is a big problem. 

Some common and even excellent methods in 2D movies cannot be used in 3D movies. In 3D movies, some techniques that were not in 2D movies need to be developed. Levi is exploring all these things now.

In fact, in Levi's preparation, many troubles have already appeared.

The simplest and most direct is the issue of movie lighting. 

When shooting a 3D movie, simulating the imaging principle of human eyes, the micro-smile parallax of the two frames constitutes a sense of distance, creating a stereoscopic illusion. 

This shooting method determines that there are many things to pay attention to in the use of light compared to single-camera shooting.

For example, glass reflects light. In single-camera shooting, it will only form a glare, and there is nothing worth noting in shooting. But if it's 3D shooting, the same piece of glass, because of the different angles of the two lenses, will reflect two different glares with differences in position and shape. This image naturally cannot be used.

This small problem reflects a big difficulty. In movie shooting, sometimes, light is the best magician. Glare, prism, filter, covering the lens, shooting through glass of different colors, different angles — all these have become important means of shooting 2D movies. But in 3D movies, these things need to be reconsidered in terms of shooting.

And not only light but also color. In terms of color matching, too many dark tones cannot be used in 3D lenses to highlight the sense of hierarchy. However, a movie's shooting must have a color tone. How to ensure normal colors and make them acceptable to people is also a problem.

Moreover, besides these, there is also the issue of the photographer — In single-camera shooting, blurring some areas in one shot can highlight certain points well. But in 3D shooting, how this can be achieved is also a test for the photographer.

Levi has never mentioned these things to Alexander, but Alexander is very clear that none of these is easy to achieve. Levi has put in a lot of effort to achieve the best in all these. 

And what he said is not wrong — making a good movie is his ideal. But shooting a movie that can make a lot of money is also Alexander's ideal.

Everyone is working hard for this, and no one is relaxed. For example, in the past two days, what Levi has been doing is adjusting the interaxial distance, which is a very troublesome job.

Interaxial distance is the most critical parameter that determines the 3D effect seen by the audience. It refers to the distance between the optical center axes of the two lenses when shooting in 3D. 

Interaxial distance determines parallax, and the brain obtains depth information through two images with parallax, ultimately forming a stereoscopic image.

And how to determine this distance is Levi's current job.

In fact, without considering comfort and correctness, the relationship between interaxial distance and 3D effect is very simple. The larger the interaxial distance, the more obvious the 3D effect, and the audience feels a stronger sense of depth in the picture. The smaller the interaxial distance, the weaker the 3D effect, the weaker the depth perception, and this rule is extremely simple.

However, in reality, comfort and correctness cannot be ignored. An excessively large interaxial distance may seem to create a great image, but it can also easily lead to other consequences. 

One consequence is the miniature effect — because the depth is too great, it is easy for the audience to have a mistaken perception that things in the picture are abnormally small. 

Another more troublesome one is that the image cannot be integrated into a three-dimensional image in the brain — this trouble, if it's just the inability to see the stereoscopic effect, it's just a small matter. The greater possibility is that the audience will feel dizzy, have a headache, and cannot appreciate the movie at all.

If the interaxial distance is too small, the trouble is naturally that the 3D effect is not obvious, and it looks not much different from a flat picture. Such an image is naturally unusable.

Therefore, before shooting a 3D movie, the interaxial distance of the 3D movie is generally determined using a laser rangefinder, a process that is not specifically assigned to anyone and is now being done by Levi with the crew, which is naturally very difficult.

However, if you want to be the first to shoot a 3D movie, you must endure some trouble.

"In fact, we have gained something. Now, I have basically found the interaxial distance for shooting. We are becoming more and more familiar with these machines — not only that, but I am also thinking that maybe we can train stereographers so that they can work for other people's movies in the future. Believe me; our movie will definitely be well-shot. This is absolutely not boasting."

Although there were numerous difficulties, Levi's preparation work was very smooth. After all, he has some memories that greatly help him.

In his memory, there is a widely accepted 1/30 law for 3D photography: that is, the interaxial distance should be 1/30 of the distance from the eyes to the object being photographed. 

In other words, if you are shooting a scene where the main subject is, for example, 30 feet away from the camera, the interaxial distance between the left and right lenses should be about 1 foot (30 feet / 30 = 1 foot). This rule aims to provide a comfortable and natural stereoscopic effect, enhancing the viewer's perception of depth without causing discomfort or distortion.

This rule has been summarized after countless failed experiments, and now it is also benefiting him greatly.

However, the screens for movie playback are different, and naturally, there will be differences in detail. IMAX screens are very large, so how to project a movie on such a screen and how to adjust the interaxial distance has been Levi's focus of work in recent days.

Alexander knows all these things, and he also knows that Levi has done the best job finding the interaxial distance so quickly.

"Since you think it will definitely work, then you continue to work hard. Anyway, our money has already been thrown in, and we have to get some results. Otherwise, we will lose big." 

Alexander sighed, but Levi immediately responded, "Don't be silly. Haven't we just earned a big sum recently? The movie 'X-Men 3' has just been released, and it's a big hit, right?"

*****

Thanks and kudos for my patreons 

Marcelo Maia

Britanna

Mandy G

Scott DePaepe

Oluwatimileyin Olayemi

Herylle Ian Gloria

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