Light field cameras are not mere optical freaks borne out of complicated mathematical calculations. They are much more than that. And yet they are truly amazing when you see the results produced by these cameras for the first time. Light field cameras use many of the same optical concepts that power today’s cameras, but they go just a tad beyond ordinary cameras to produce results that are known in photography parlance as ‘Living Images’. In this short but informative video, Dr. Mike Pound from the University of Nottingham explains the science behind light field cameras:
Shifting Focus After You’ve Taken the Image
With modern cameras, once you’ve acquired focus and taken an image it’s impossible to change the focus point or the angle of view afterward. With light field cameras these are exactly the things that you can accomplish. Click on any section of the image and that section rocks into focus. Sound like technology from Star Trek? Not really. Light field cameras use a concept that creates tiny micro-images which allow you to shift focus across different areas of an image after you have taken it.
Dr. Mike Pound from the University of Nottingham demonstrates a light field camera.
So, basically you no longer have to worry about focusing any more. Aim and shoot – that’s all it takes to get going. Depending on the size of the lens you can even toggle between several points of view. These are something unimaginable with a regular camera. Of course there are some constraints. You can only do this using proprietary software and then there is a limitation in the image quality. But the implications are simply too irresistible.
How Does a Light Field Camera Work?
Unlike a regular camera, where light traveling from a point is bent by the lens and then converges at a corresponding point at the back of the sensor, in a light field camera there are millions of tiny micro-lenses that come into the picture before the light rays reaches the sensor.
The tiny array of micro-lenses in front of the sensor
These micro-lenses sit just in front of the sensor. Their job is to collect light rays traveling from a specific section of the scene. They not only capture the color information but also the orientation at which these light rays travel. In a traditional camera that orientation information is never captured—only the color information. Additionally, in a traditional camera the light rays converge on the sensor while in a light field camera those rays converge on the micro-lenses sitting in front of the sensor. But the micro-lenses don’t capture the images, the sensors do! So light rays travel further and reach the sensor at which point they are traveling further away. Technically the image should be blurred, going by what we have seen in traditional cameras.
So how is this happening? To quote Dr.Pound,
“If we pick an individual pixel under a micro-lens, all the light going through that pixel comes from the same place on the main lens. So, this pixel only ever sees light entering it at that point.”
Another explanation he gives is,
“Every ray that passes through this sub aperture hits all the different micro-lenses and always ends up on the same corresponding pixel underneath each micro-lens.”
Light Field cameras capture not only light information but also the orientation information
“What we have essentially done is not just obtained orientation but have also obtained loads of tiny little images that view the scene from all over the main lens. Another way to look at it is that these micro-lenses are just tiny cameras taking a picture off the back of the main lens. And of course they are going to have a different view because some of them are on the left and some of them are on the right.”
One major application of light field cameras is definitely in creating the parallax effect, where a slight change in perspective can be obtained due to the unique way in which the tiny micro-lenses sitting inside the camera essentially produces an array of images instead of a single image. The other application is in refocusing.
What do you think of light field cameras? Are you ready to try one out?
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This article creates more questions than it answers.
The first quote from Dr. Pound says “all the light going through that pixel”. How does light go through a pixel? I understood that a pixel captures light and doesn’t pass the light through.
He also says, “these micro-lenses are just tiny cameras”. So does each array of micro-lenses have a full set of sensors behind them? So that each point on the sub-aperture is captured by a matrix of pixels?