As the smartphone camera gains an ever-more sophisticated role in the science classroom, the technical limits of phone photography become more apparent. Luckily a dose of strong light can overcome many problems as well as provide access to a world unseen by the human eye. But not just any light will work. The amount, color and frequency modulation of the light all play important roles in scientific photography.
The proper amount of light is a double-edge light saber. Many LED light sources change the brightness by blinking the LED very fast. Unfortunately that blinking can be detected by the camera and shows up in video as flickering lights or dark bars moving across the screen. And the effect is even more pronounced when the slow motion option is engaged. An excellent solution for just such lighting problems is now available with the Surefire FirePak.
Photons from a Phirehose
Surefire is well known as the maker of some of the world’s best flashlights, but recently they have let some of their lighting magic seep into the world of smartphones. With Surefire’s new “FirePak Smartphone Video Illuminator + Charger” lighting system, two troublesome areas of cell phone photography and video capture are solved with one powerful device. By blasting up to 1500 lumens of light onto a subject, the very fast or the very dark are now fair game for the camera. 1500 lumens is about the same as a focused 100 watt light bulb!
Leveraging the sophisticated camera and image processing power of a student’s smartphone can open even more windows into the the high speed, very small and of course, nighttime and dark areas. In fact until you use such a light that is both powerful in output and features, it’s hard to appreciate all the limitations of even the most modern smartphone cameras.
The FirePak is designed for the phone camera and is billed as a mobile lighting solution and device charger. The lightly rectangular block named the FirePak contains a large rechargeable battery, two USB ports (one for charging itself, one for charging other devices), a sliding multi-position switch, a battery indicator light, and most of all two unique LED lights.
What’s unusual about the pair of LED lights is they have asymmetrical 10mm reflectors with one offset in one direction and the other offset 180 degrees. This combination of lights produces full-frame illumination specifically designed for a smartphone’s 16:9 HD aspect ratio. In other words, the FirePak lights up a rough rectangle that is proportioned to what the cell phone camera sees. No wasted light, no dark spots or vignetting.
Proper exposure is a combination of three things: shutter speed, lens aperture, and light sensitivity. In the case of slo-mo, the shutter time is very short and the light sensitivity of the camera chip is fixed and depends on the quality of the smartphone. So too is the aperture of the camera’s lens. So the solution is to pour more light on the subject and that gives the camera more to work with in terms of focus, exposure, and a better chance to clearly freeze each frame.
The Surefire FirePak has a six position switch, off—on (but no-light)—low—med low—med high—high. When on but no-light, the light output can be controlled by the App up to 10 meters away (which has its own set of advantages). In the video below, the FirePak is cycled from off through high and back to off. It was not mounted on a smartphone so that is why the light was moving relative to the camera’s view.
The runtime for the FirePak on high output is about five hours with a slowly diminishing brightness. You might get about one and a half complete iPhone recharges if the FirePak’s battery is used only for that purpose. And running on the lowest light output of 100 lumens, the FirePak should give about 10 hours of useful light off a full starting charge. Obviously there are many combinations of the above, but you can always head off to school with a full charge if you plug the FirePak into a wall outlet or computer overnight. And you can even charge the Firepak with a traditional external recharging cell phone battery such as any of those so popular today, but the FirePak has a healthy appetite given its own large battery so don’t expect to pull a full charge out of a similar sized backup battery.
Another important feature of the Surefire FirePak, and arguably the most impressive, is that the LEDs are modulated at a frequency faster what the smartphone camera uses, even with slow motion. Lesser lights blink on and off rapidly to simulate a dimmer output. But that blinking can be seen by the smartphone camera and appears as flashing or dark lines on the captured video. During higher speed video capture (that produces so-called Slo-Mo results) the effects are even more pronounced. In the past, our lower powered incandescent lights produced a constant photon output even when dimmed. In fact it was the electric current of 60 cycles of AC current (in America) that produced blinks and flashes rather than the dimming.
Although taking pictures and video at night or in a dark environment might seem the obvious use for the FirePak, the lighting of subjects that will be videoed in slow motion is truly a win for the FirePak. For a camera to capture video that plays back in slo-mo, it must capture two, three, four or more frames in the time it normally captures one. So half-speed slo-mo is about 60 frames per second or twice the normal 30 FPS. Quarter speed playback meaning one second of real time is shown over four second would take 120 FPS. And the iPhone’s slo-mo is 240 frames per second or eight times normal. And some other Apps claim up to 1000 frames per second. So with all that speed comes the need for lots of light.
The Surefire FirePak produces a bright stream of light that can easily reach out 20 meters or more when needed, or shine a spotlight on a local scene making closer subject stand out from the background. The low setting of the variable output FirePak is still fairly bright so for closeup photography and video so it may be necessary to hold the FirePak further away from the scene, even if just centimeters. Light output is affected by the inverse square law meaning that the light’s intensity is inversely proportional to the square of the distance from the source. So even a little increase in subject-light distance has a noticeable effect.
The Case in Point
The FirePak is designed to be mounted to the smartphone using a slide-on docking attachment system that begins with a custom Surefire phone case. The dual-rail yoke on the back of the FirePak slides into a pair of slots on the back of the svelte phone case Surefire makes. It’s mostly held in pace by friction, but there is a mild stopping block that locks the sliding. But overcoming the block and following friction to separate the two is done by just sliding them apart. No buttons or release levers.
The FirePak is reversible on the phone case, and I’ve found that when imaging close objects such as those within 20 cm from the lens, the output reflectors on the FirePak might need to be close to the lens to reduce shadows. For everything else, the FirePak can be reflectors up or down. For off-phone use, I think a tripod socket on the FirePak would be helpful, or just an after-market tripod attachment that uses the same rails as the smartphone case.
At about 38 seconds into the Surefire promotional video below, you can see the blinking from a modulated light source on the curtain in the right of the frame just before the FirePak overwhelmed the scene with flicker-free lighting.
In the video above, I had to study how Surefire was using the FirePak on a stand during the filming since the FirePak was the actual lighting source for the video. Surefire was using a clamp to hold the FirePak. I had hoped to repurpose one of my iPod/iPhone tripod clamps, but alas, the FirePak is too narrow to seat in a traditional sized iPhone clamp. However, being a photographer in a former life, I did have plenty of Bogen/Manfrotto clamps and arms for studio work, as well as tripods. Using a similar solution to Surefire’s video, I was able to position and adjust the FirePak for all smartphone photography and video shooting situations I could create. Of course duct tape would also work. And it is with this off-camera lighting that the Bluetooth App control of the FirePak really shines!
There’s an App for that.
The Surefire FirePak will sell for about $200, but has an accompanying free App called the Surefire FirePak Illuminator that can be downloaded onto your Apple or Android phone. The App can talk to the FirePak via Bluetooth allowing some on-screen light control and customization. Additional features of the App include grid overlays for photo composition, tools for white balance, a self-timer, output levels, exposure brightness (ISO), and Bluetooth controls including battery percentage.
With the dust settling on this new space of high quality studio lighting for a smartphone, it is clear that the trend of student smartphones is not really a trend anymore. It is the new normal. And with all paradigm shifts in capabilities, we as teachers should make sure there is plenty of room in our expectations to address and even assess what might have been impossible last semester.