A Hands-On Review of the Interfit S1 Flash

Monolights cutting loose from powercords are becoming as popular as disgruntled consumers ditching their cable provider. The latest lighting manufacturer to cut the cord is Interfit, with their new S1. But there’s a lot more to this flash than its power source. The S1 offers both TTL and High Speed Sync (HSS), IGBT technology to regulate power flow and, to make life easier, it can be powered by AC using the bundled international multi-voltage AC adapter. Interfit charges $1,000 for the S1 and also sells an S1a model that is AC-powered only.

I tested the light in my home studio, as well as in a larger, off-site studio during a shoot with a dancer. For the latter, I mainly shot with the Nikon D4S and a NIKKOR 24-70mm f/2.8 lens, triggering the flash with Interfit’s optional $100 transmitter (available for Nikon and Canon) or with PocketWizard Plus IIs using the S1’s sync port. To match the light’s portability, most images were captured using a small Interfit collapsible softbox.

With a maximum output of 500Ws, the light provides 7 stops of power (2.0-8.0), adjustable in 1/10th stop increments for both TTL and manual modes. HSS is available in manual mode with sync speeds of up to 1/8000th of a second. Prior to receiving the test unit, Interfit updated the original firmware to allow the use of third- party HSS transmitters, which they tested with the PocketWizard TT5 and the Yongnuo YN622 (Interfit said they worked perfectly). I successfully shot in HSS mode using the Interfit transmitter and Nikon’s Auto FP high-speed sync, which worked flawlessly.

Author Theano Nikitas tests out Interfit’s S1 flash during a shoot with a dancer. Both photos © Theano Nikitas.

Design

The S1 weighs 6.3 pounds and measures 13.4 x 9.1 x 5.1-inches, light and small enough to pick up by its built-in handle and take on the road. The battery is integrated into the body, allowing the light to maintain its cylindrical shape and is easily removed for charging. Although built solidly enough for travel, as with any piece of electronic/optical equipment, it’s important to pack it carefully. The light tube is covered with a frosted glass dome and the light comes with a plastic protective cap. A small reflector is also included in the bundle.

On-flash controls are minimal, but perfectly sized for easy access and well positioned below the large and bright LCD. The Interfit transmitter, powered by AAA batteries, is fairly low profile and fits into the camera’s hotshoe, with easy-to-operate controls.

What We Liked

Given the tiny space that I call my home studio, anything that’s cable-free gets my vote. But even in a larger studio setting, working with an untethered light made it easy to adjust positions without worrying about finding an outlet or tripping over a cable.

The 4500mAh Li-ion battery is rated for an impressive 350 full-powered shots per 3-hour charge, but since I rarely shot at full power, I never had to use the second battery that I had on hand. The optional AC power feature ensured that I had a backup if/when needed. Battery levels are visible on the light and transmitter LCDs, and, as a nice touch, the battery has its own power indicator.

Overall, TTL worked very well and the S1’s 5700K color temperature was, for the most part, consistent across exposures (albeit just lightly warm when the D4S white balance was set at 5700K). Of course, being able to shoot HSS so easily is a huge benefit, as is the ability to steplessly dial in adjustments. Importantly, the unit and the transmitter are extremely easy to use, and the transmitter has a micro USB port for user-installable firmware updates.

What we Didn’t Like

Recycle times can’t be fast enough, especially when photographing dancers, and I found that I had to really pace myself to wait for the S1’s beep to sound when it was recharged. At between 2 to 3 seconds (the latter for full power), the S1’s recycle times weren’t bad but I’d prefer a shorter wait between shots.

The modeling light offered only three options: off, 50 percent and 100 percent, while I’d love to be able to manually dial the power up and down. The battery, which comes with its own power adapter for charging, has to be removed from the unit and charged separately. When queried about why the battery cannot be charged in the unit when the light is in AC power mode, Interfit explained that doing so would negatively impact the longevity of the battery since the battery would be “continuously charged and discharged.” That makes total sense and it’s certainly worth the 10 seconds it takes to remove the battery for charging.

How It Compares

Despite some nitpicks here and there, we think that Interfit’s S1 will find its way into lots of photographers’ kits for both location and in-studio assignments. Given its multiple power options, TTL and HSS in a single package, the Interfit S1 Flash is a solid option that fits neatly between battery-powered monolights like the $2,000 Profoto B1 500 AirTTL and Flashpoint’s $600-priced Rovelight 600. While the Interfit S1a, with AC power only, is a good value at $600, the S1 offers a lot more flexibility and bang for the buck.