As most of the Wetpixel community is probably aware, Wetpixel publisher Eric Cheng is also Director of Photography for the ground-breaking Lytro light field camera. Recently, Eric took one, in a custom Nauticam housing with Light & Motion SOLA 2000 lights, with him on the Wetpixel Ultimate Indonesia expedition, and has just published the results. Wetpixel caught up with Eric to hear more about light field photography, and how it performed underwater:

In order to interact with the Lytro images, click on any part of it and the photo will automatically update its focus to that point. Clicking and dragging gives you the ability to shift perspective, while double-clicking will zoom in. (Images by Eric Cheng unless otherwise credited).

Wetpixel: Eric, can you give an overview of how the Lytro camera works, and what makes it different to conventional cameras?

Eric: The Lytro camera is the world’s first consumer light field camera. Light field cameras capture the raw light field, which contains information that is fundamentally different than what is contained in pictures taken by traditional cameras (from plate cameras to modern digital cameras). The light field contains directional information, which means that the smallest unit of a light field image is no longer a pixel; instead, it’s a pixel plus a direction in 3D space, or what we call a ray. The first Lytro light field camera is a consumer camera that captures 11 million rays of light field data (rated as 11 “megarays”). A light field engine-the light field version of a raw converter—processes the raw light field data and outputs a projection in 2D space, which looks just like a normal picture. The difference is that we can project multiple 2D pictures from a single light field picture.

A light field camera and software virtualizes many components of the camera using the combination of a light field sensor, light field system design (the design of the camera), and algorithms that project 2D images from light field data. This is powerful for both the photographer and the end user; both photographers and viewers can refocus pictures after the fact and do something we call “Perspective Shift,” which allows you to change the center of perspective after the fact. It’s like going back to that moment of capture and moving the camera around: left, right, up or down, which reveals the fundamental 3D nature of light field photography. All light field pictures are inherently 3D.

Wetpixel: The ability to give the viewer some power over the creative process is unique. How do you think it will impact underwater imaging?

Eric: First, it will allow interactivity within a single moment. Refocus and perspective shift reveal more about the moment of capture than does just looking at a 2D picture. I’ve always loved the underwater world because diving is sort of like flying. The ability to move up and down adds a dimension of freedom to the world, and because all underwater animals (and the environment) have the ability to move in that new dimension, the underwater world feels much more 3D. Underwater 3D pictures and video have always been fascinating as things float about, and you can really feel the depth as you look around. So I’m particularly interested in the idea that 3D capture gets easier with light field photography.

Refocus is also interesting, and allows the use of longer focal lengths and bigger apertures without having to worry as much about focus. Of course, we don’t (yet) have the cameras nor underwater housings / accessories that allow people to experiment with underwater light field photography, but when it does arrive, it should be very interesting.

Wetpixel: How long have you been using Lytro cameras underwater?

Eric: I first took a Lytro camera underwater at the end of 2011, and again a couple times in 2012.

Wetpixel: So how did it perform underwater during the Wetpixel Ultimate Indonesia Expedition?

Eric: The camera performed well, especially given that the Lytro camera hasn’t been optimized at all for underwater use. There is a lot to think about when shooting in light field: everything is a relationship in depth, and it all lives in the world of optical depth of field. Depth of field, as most serious photographers know, is non-linear, which makes it difficult for people to internalize. One thing that most people don’t realize is that light field pictures are most effective when depth of field is shallow. Imagine taking a camera with a fisheye lens and trying to achieve a shallow depth of field—it’s almost impossible! So light field certainly has its challenges, both from a photography point of view, and from the point of view of a typical consumer who has no knowledge about depth of field in photography.

Wetpixel: How did you light the subjects?

Eric: I used continuous lighting. I own a couple Light & Motion SOLA 1200 lights, but Light & Motion graciously lent me two SOLA 2000 lights for these shoots, each of which emit 2000 lumens of light. Underwater photographers know this well: If you don’t bring your own full-spectrum lighting, everything will be green and blue in your resulting pictures. So lighting is key.

Wetpixel: What controls do you have on the camera? Did the housing mimic these controls?

Eric: I have full control of the camera from the housing, including zoom, shutter, power, Creative Mode (which allows tapping the rear touchscreen to control refocus), and manual exposure. The housing sort of mimics the controls—it has a couple buttons for zoom, a shutter lever, a power button, and 3 buttons that touch the rear LCD. I used custom firmware that translates the normal gesture-based interface into a tap interface. This isn’t available to the general public.

Wetpixel: I notice that the housing is branded as a Nauticam. Is it a custom housing? Do you know if it will be released commercially?

Eric: We worked with Nauticam to produce a prototype housing. There is always a possibility of a commercial housing at some point in the future, but the viability of a housing that can fully control the housing is hinged upon the release—and support—of firmware from Lytro that can translate gesture-based control to tap-based control. Either that, or a housing manufacturer must create a housing that supports gestures, which is not easy. Someone might also eventually use the USB port to control the camera, but that is unlikely until we officially provide some sort of documented interface.

Wetpixel: The images are mostly macro subjects, is this because the camera performs better with this type of subject?

Eric: I did shoot some pictures with a wide-angle lens (the housing has a 67mm thread on the front so it can accept wet lens adapters), but they created a huge depth of field, requiring front subjects to be just a few inches away. As I mentioned above, large DoF isn’t great for light field capture, and the resulting images are basically 2D unless there is a subject that is very, very close. I chose not to show those because they are very close to normal pictures one might achieve with a 2D, traditional point & shoot camera.

Wetpixel: Creatively, how does the light field capture process affect how you take images?

Eric: I think very much in 3D when I’m taking light field pictures. Specifically, I think in 3D, but in terms of depth of field. This isn’t really 3D in the way we typically think of 3D. When I’m shooting wide-angle, I think of everything further than around 5’ away as being at infinity, and I think of the space between 6” and 1 foot as being huge. At longer zooms, everything stretches out, so suddenly, I’m thinking about spaces between 10’ and hundreds of feet as being viable for interesting light field capture from our camera.

It’s dangerous to map what I’m saying to all light field photography, though. Different light field cameras will perform differently. A light field camera with a huge sensor and aperture will be suitable (in the light field domain) for different sorts of captures than is a camera with a point & shoot-sized sensor (i.e., the current Lytro camera).

Wetpixel: Can you see a time when light field cameras will replace conventional ones?

Eric: I see a time in which light field cameras will complement conventional cameras in the main stream. Light field cameras always have a resolution disadvantage in the 2D space when compared to conventional cameras, so people who need high resolution capture will gravitate towards conventional cameras. But when light field cameras can take pictures that are high enough in resolution to be indistinguishable on common displays, there may be no real reason to shoot conventional over light field.

*Wetpixel: Can you give any tips for people using Lytro cameras? Underwater tips? *

Eric: Sure! Think in 3D, and think about depth of field. The Lytro camera’s live view sees the world as a normal camera does at f/2, so things can still get blurry in the LCD. Blur for us is a bit counterintuitive. Something blurry in the rear LCD means that you’ve achieved a shallow depth of field in your composition, which is a good thing. So if you don’t see something blurry in live view, you won’t have compelling refocus in your resulting living picture. 3D and Perspective Shift is tied to refocus potential, so your goal will be achieve a shallow depth of field. This is also who you see mostly macro shots in the gallery. With a small sensor, the only way I can achieve a shallow depth of field is by getting close, or shooting long focal lengths. While the camera does achieve an absolute focal length of over 40mm (~340mm equivalent in 35mm terms), the field of view at 40mm is really narrow, so compositions need to take that into consideration.

Underwater tips? As always, dive skills are the most important thing. You should be able to hold and use a camera underwater without destroying the environment around you. Also, it helps to have internalized all of the tips that make light field shooting successful so you don’t have to think about them too much when you’re in an environment that is trying hard to make you fail.

More: You can see my light field pictures on my Lytro image gallery, and the underwater Indonesia light field gallery is here.