MarkBarbieri
Semi-retired
- Joined
- Aug 20, 2006
- Messages
- 6,172
OK, I finally produced a 3D picture. I'm going to do a 3D video this weekend. Here's what I've learned. This is all coming from someone that just barely understands anything about 3D, so please correct my mistakes and add anything you think will be of value.
3D works by showing a different image to each eye. That's the way you see the real world. Each eye is separated by a couple of inches and has a slightly different view of the world. When your brain processes the image, things that shift a lot from one eye's image to the other's are assumed to be close and things that don't shift much are assumed to be far away.
Back in the 1800's, people started making 3D photos. They took two photos from cameras placed side by side. They mounted the resulting images next to each other on a card. The made viewers that forced each eye to see a different picture. The result was a 3D image.
The fundamentals haven't really changed since then. 3D photos and videos are still created by recording the images from two nearby locations and showing the resulting images to each eye separately. What has changed is how we store the images and how we direct them to each eye separately.
In the 1950s, we started making 3D movies. We recorded them with two cameras side by side. To play them back in 3D, you used two projectors and showed the image on top of each other on one screen. To get each eye to see a different image, we put a polarizing filter on each projector and on each eyeball (those glasses they give you at the movies). On one side, we polarized so that only light waves going up and down would be visible and on the other side, we polarized so that only light waves going side to side would be visible. As a fun trick, take two pairs of 3D movie glasses and place them in front of each other. If you line up the left lens with the left lens, you can still see through it. If you line up the right lens with the left lens, you can't. That's because the left lens filters out one polarized direction of light and the right lens filters out the other. If you combine them, they filter out everything.
Having two projects with polarizers was deemed to be too complicated for home use, so other tricks were tried. The simplest was to use a pair of glasses with a blue filter on one eye and a red filter on the other. If you make the movie with stuff that the left eye is supposed to see in blue and stuff that the right eye is supposed to see in red, each eye gets a different view and you get a 3D looking image. Unfortunately, this jacks with the color of the image and doesn't look very good.
The new Blu-ray standard takes a different approach. With it, you wear a special pair of battery powered glasses. The glasses watch for a special signal from the TV. When it sees the signal, the left eye goes completely dark so that you can't see through it. Then it opens and the right eye goes dark. They switch back and forth 120 times every second, so each eye gets 60 looks at the screen each second. Every time the TV sends a signal to the glasses to switch, it changes the image that it shows. In this way, it lets the left eye see the image designed for the left eye and the right eye see the image designed for the right eye.
There are two standards for how to produce images that work on these 3D TVs. Both standards work on all new 3D TVs, so you don't have to worry about a format war. 3D TVs are just like normal TVs most of the time. It's only when you switch it into 3D mode that it starts doing the image switching stuff. For people wearing the glasses, they see everything in 3D. For people not wearing the glasses, they see a fuzzy picture similar to what you see at a 3D movie when you take off your glasses.
The standard that TV stations (like ESPN's new 3D channel) use is called "side by side". They take the video for each eye and squish it so that it is half as wide as normal. They put those together side by side so that it is one image that is the same size as a normal picture but with two squished images next to each other.. With a normal TV, it will be like watching two videos that looked squished next to each other. With a 3D TV, the TV will stretch each half of the image so that it looks normal. It will switch back and forth between each image very rapidly and in time with the glasses so each eye will see what looks like a normal image. The result is a 3D image that has half the horizontal resolution of a normal image.
The standard for 3D Blu-ray stacks the images one on top of the other. It takes a 1920x1080 image for the left eye and puts it on top of a 1920x1080 image for the right eye. The result is a 1920x2160 image. A normal TV wouldn't no what to do with it, so I don't think it would show anything. A 3D TV can show it in one of two ways. It could just show the top half (the part recorded for the left eye) and it would look like a normal 2D picture. In 3D mode, it would switch between the top and bottom parts syncrhonized with the glasses. This results in a 1920x1080 image like a normal Blu-ray.
The TV companies prefer the side-by-side because it is easier. It requires no more bandwidth than a normal HD image. In fact, once the video is made as a side-by-side video, I don't think that the satellite/cable/TV tuner needs to do anything different than normal. The TV handles the splitting and stretching stuff. That should mean that 3D TV stations will work with any 3D TV regardless of tuner.
I still don't know of a cost effective way to make a 3D Blu-ray. The encoders I found rarely had prices and those that did were several thousands of dollars. Making a side-by-side 3D image is easy. I did it by taking two cameras, setting them side-by-side, and taking a picture with both of them. I squished them to 960x1080 pixels wide, combined them into a single 1920x1080 pixel image, and displayed it on the TV. When I switched the TV into side-by-side 3D mode, it looked like a 3D image. Here is the shot I used as a test:
To get matching images with equipment I had on hand was a bit tricky. I used two tripods that I set up very close to each other and as level as I could get them. I used a Canon 5D Mark II and a 7D to take the pictures. The challenge there is that one is full frame and the other is a 1.6x crop. I used a 24-105 lens on the Canon and a 17-40 lens on the 7D. I zoomed the former to about 35mm and the latter to about 22mm so that the field of view matched. To match the DOF, I set the aperture on the 7D one stop wider (f/9 vs f/13) to accommodate for the larger sensor. I compensated by making the ISO one stop lower on the 7D (100 vs 200).
My next step is to take video simultaneously from each camera. The new challenges with video are synchronizing the video and combining them. I'll handle the sync by recording a clapper so that I can match the moment of the clap in each video stream. I found some software called NeoHD by Cineform that will combine the video streams. Once I combine them, I should be able to output them as a normal H.264 video stream and play that back on the TV. In theory, that should give me a 3D video.
There are a lot of complexities that I don't understand. What is the impact of the difference between the cameras? What is the impact of the angle (making them a bit cross eyed or straight ahead)? How close can objects get to the cameras before the effect is strained. How much DOF should I have for the best effect?
My primary goal is just to see if I can do it. Given all of the challenges in making it work, I don't think I'll make a habit of shooting 3D videos. 3D pictures might be fun for occasional use. If I decide I like them, I'll buy a bar that mounts on my tripod and allows me to mount two cameras. I might also buy some matching camera/lens combinations to get better results.
What's the future of 3D video? Beats me. I suspect that it will not replace 2D TV any time soon. I don't know of any technology on the horizon for allowing people to watch 3D videos without the glasses. I saw a demo of a low res CRT that did it, but you had to stand directly in the middle and a certain distance from the screen. That's not real practical for home use.
I can see 3D TV setups becoming moderately popular in home theater setups to use for special events. It might fill a niche somewhat like laserdiscs did. It won't be the dominant format but it might survive as a popular secondary format. The biggest advantage that it has is that it is a very inexpensive feature to add to TVs and Blu-ray players, so in another year or two, most will be equipped to handle it.
The current crop of glasses are hideously uncomfortable (at least on my head) and are quite expensive (over $100 a pair). We got a 2 pairs free with our TV and Blu-ray player. I don't feel compelled to buy two more so that the whole family can use them. That's especially true since Monsters vs Aliens seems to be the only 3D Blu-ray available and only a few more are planned for this year. I'll probably check out ESPN 3D, but I doubt that the 3D effect will be worth the bother for me at this time.
Anyway, it's something that I am having fun playing with so I thought I'd post about it here.
3D works by showing a different image to each eye. That's the way you see the real world. Each eye is separated by a couple of inches and has a slightly different view of the world. When your brain processes the image, things that shift a lot from one eye's image to the other's are assumed to be close and things that don't shift much are assumed to be far away.
Back in the 1800's, people started making 3D photos. They took two photos from cameras placed side by side. They mounted the resulting images next to each other on a card. The made viewers that forced each eye to see a different picture. The result was a 3D image.
The fundamentals haven't really changed since then. 3D photos and videos are still created by recording the images from two nearby locations and showing the resulting images to each eye separately. What has changed is how we store the images and how we direct them to each eye separately.
In the 1950s, we started making 3D movies. We recorded them with two cameras side by side. To play them back in 3D, you used two projectors and showed the image on top of each other on one screen. To get each eye to see a different image, we put a polarizing filter on each projector and on each eyeball (those glasses they give you at the movies). On one side, we polarized so that only light waves going up and down would be visible and on the other side, we polarized so that only light waves going side to side would be visible. As a fun trick, take two pairs of 3D movie glasses and place them in front of each other. If you line up the left lens with the left lens, you can still see through it. If you line up the right lens with the left lens, you can't. That's because the left lens filters out one polarized direction of light and the right lens filters out the other. If you combine them, they filter out everything.
Having two projects with polarizers was deemed to be too complicated for home use, so other tricks were tried. The simplest was to use a pair of glasses with a blue filter on one eye and a red filter on the other. If you make the movie with stuff that the left eye is supposed to see in blue and stuff that the right eye is supposed to see in red, each eye gets a different view and you get a 3D looking image. Unfortunately, this jacks with the color of the image and doesn't look very good.
The new Blu-ray standard takes a different approach. With it, you wear a special pair of battery powered glasses. The glasses watch for a special signal from the TV. When it sees the signal, the left eye goes completely dark so that you can't see through it. Then it opens and the right eye goes dark. They switch back and forth 120 times every second, so each eye gets 60 looks at the screen each second. Every time the TV sends a signal to the glasses to switch, it changes the image that it shows. In this way, it lets the left eye see the image designed for the left eye and the right eye see the image designed for the right eye.
There are two standards for how to produce images that work on these 3D TVs. Both standards work on all new 3D TVs, so you don't have to worry about a format war. 3D TVs are just like normal TVs most of the time. It's only when you switch it into 3D mode that it starts doing the image switching stuff. For people wearing the glasses, they see everything in 3D. For people not wearing the glasses, they see a fuzzy picture similar to what you see at a 3D movie when you take off your glasses.
The standard that TV stations (like ESPN's new 3D channel) use is called "side by side". They take the video for each eye and squish it so that it is half as wide as normal. They put those together side by side so that it is one image that is the same size as a normal picture but with two squished images next to each other.. With a normal TV, it will be like watching two videos that looked squished next to each other. With a 3D TV, the TV will stretch each half of the image so that it looks normal. It will switch back and forth between each image very rapidly and in time with the glasses so each eye will see what looks like a normal image. The result is a 3D image that has half the horizontal resolution of a normal image.
The standard for 3D Blu-ray stacks the images one on top of the other. It takes a 1920x1080 image for the left eye and puts it on top of a 1920x1080 image for the right eye. The result is a 1920x2160 image. A normal TV wouldn't no what to do with it, so I don't think it would show anything. A 3D TV can show it in one of two ways. It could just show the top half (the part recorded for the left eye) and it would look like a normal 2D picture. In 3D mode, it would switch between the top and bottom parts syncrhonized with the glasses. This results in a 1920x1080 image like a normal Blu-ray.
The TV companies prefer the side-by-side because it is easier. It requires no more bandwidth than a normal HD image. In fact, once the video is made as a side-by-side video, I don't think that the satellite/cable/TV tuner needs to do anything different than normal. The TV handles the splitting and stretching stuff. That should mean that 3D TV stations will work with any 3D TV regardless of tuner.
I still don't know of a cost effective way to make a 3D Blu-ray. The encoders I found rarely had prices and those that did were several thousands of dollars. Making a side-by-side 3D image is easy. I did it by taking two cameras, setting them side-by-side, and taking a picture with both of them. I squished them to 960x1080 pixels wide, combined them into a single 1920x1080 pixel image, and displayed it on the TV. When I switched the TV into side-by-side 3D mode, it looked like a 3D image. Here is the shot I used as a test:
To get matching images with equipment I had on hand was a bit tricky. I used two tripods that I set up very close to each other and as level as I could get them. I used a Canon 5D Mark II and a 7D to take the pictures. The challenge there is that one is full frame and the other is a 1.6x crop. I used a 24-105 lens on the Canon and a 17-40 lens on the 7D. I zoomed the former to about 35mm and the latter to about 22mm so that the field of view matched. To match the DOF, I set the aperture on the 7D one stop wider (f/9 vs f/13) to accommodate for the larger sensor. I compensated by making the ISO one stop lower on the 7D (100 vs 200).
My next step is to take video simultaneously from each camera. The new challenges with video are synchronizing the video and combining them. I'll handle the sync by recording a clapper so that I can match the moment of the clap in each video stream. I found some software called NeoHD by Cineform that will combine the video streams. Once I combine them, I should be able to output them as a normal H.264 video stream and play that back on the TV. In theory, that should give me a 3D video.
There are a lot of complexities that I don't understand. What is the impact of the difference between the cameras? What is the impact of the angle (making them a bit cross eyed or straight ahead)? How close can objects get to the cameras before the effect is strained. How much DOF should I have for the best effect?
My primary goal is just to see if I can do it. Given all of the challenges in making it work, I don't think I'll make a habit of shooting 3D videos. 3D pictures might be fun for occasional use. If I decide I like them, I'll buy a bar that mounts on my tripod and allows me to mount two cameras. I might also buy some matching camera/lens combinations to get better results.
What's the future of 3D video? Beats me. I suspect that it will not replace 2D TV any time soon. I don't know of any technology on the horizon for allowing people to watch 3D videos without the glasses. I saw a demo of a low res CRT that did it, but you had to stand directly in the middle and a certain distance from the screen. That's not real practical for home use.
I can see 3D TV setups becoming moderately popular in home theater setups to use for special events. It might fill a niche somewhat like laserdiscs did. It won't be the dominant format but it might survive as a popular secondary format. The biggest advantage that it has is that it is a very inexpensive feature to add to TVs and Blu-ray players, so in another year or two, most will be equipped to handle it.
The current crop of glasses are hideously uncomfortable (at least on my head) and are quite expensive (over $100 a pair). We got a 2 pairs free with our TV and Blu-ray player. I don't feel compelled to buy two more so that the whole family can use them. That's especially true since Monsters vs Aliens seems to be the only 3D Blu-ray available and only a few more are planned for this year. I'll probably check out ESPN 3D, but I doubt that the 3D effect will be worth the bother for me at this time.
Anyway, it's something that I am having fun playing with so I thought I'd post about it here.
