Light Field Photography


Context

Light field photography uses an array of cameras on the same optical plane to capture various rays of light at different angles. We can take advantage of this to simulate aperture and depth of field. The photos are taken from the Stanford Light Field Archive and are taken on a 17x17 grid of cameras.

Part 1: Image Re-focusing

We can average together the images to simulate a larger aperture and create depth of field effects that focus on objects closer or farther away. This works because as the camera moves, objects farther away move slightly while objects closer to the camera move more, when we average the images without shifting the farther away objects will have generally stayed still and stay sharp while closer objects will have more confounding light which will cause them to blur when averaged.

Using this we can shift images a certain number of pixels based on the camera position on the array in order to align closer objects and focus on them. The following is the result of various shifts, typically between -3 and 4 pixels per cell away from the center camera, to produce an animation of different focuses. The jellybeans work well for this because the depth of each object goes straight through the image, though the bulldozer is a bit more confusing as there are disjoint sections that are in focus.

Original

Refocusing


Original

Refocusing

Part 2: Aperture Adjustment

As mentioned earlier, by averaging all the images together we get a simulated large aperture, likewise, if we average fewer images we get the equivalent of a smaller aperture. My method took in an aperture diameter, and looked at the grid cells around the designated center grid cell in the radius and averaged together. I used the center grid cell,[8][8], as my center.

Pinhole Aperture, Center Image


Aperture Sweep

Full Aperture


Pinhole Aperture, Center Image


Aperture Sweep

Full Aperture

Conclusions

This was another fun project that demonstrates how simple operations can create impressive results, and even become the next big business idea! As we come to be able to capture light more accurately, the possibilities to build and rebuild our environment, or even just let a photographer take an image and tune it to perfection later, only increases. This was a great complement to the pinhole camera project.