Insects with an LED ring flash

In an earlier post I said I didn’t like flash for insect photos because it looks fake-y. But I decided to try a ring flash anyway.

Photograph of a ring flash

I like shooting on overcast days; it’s cooler, the bugs aren’t as hyperactive, and I never get a nice shot in a glaring sun anyway. But even when there’s decent light, I end up at f8 to keep ISO under 3200. I need 1/1000s to stop a plant waving around in the breeze; and there’s always a breeze.

Shooting hand-held, you’ll never get the entire bug in sharp focus – but you only need enough to make an interesting photo. I use a 100mm macro lens that can focus 6″ from the subject. At f8 the calculated DOF is a pathetic .02″. At f22 it’s double that; still not much, but better. To get there I needed more light.

I decided to try an inexpensive LED ring “flash” for about $30 (Neewer 48). I put “flash” in quotes, because this simple gizmo isn’t really a flash, just a bunch of LEDs that turn on for 1/2s when triggered. Its output is low, but I only wanted enough enough ‘fill’ to allow f16 or f22 at reasonable ISO – and obviously, for insects, I’ll be very close.

The “flash” worked as advertised, with my Nikon Z6. But there was a problem to solve.

When I first tried shooting an insect at 1/1000s, I could hardly tell the difference between having this light on, or off; it just wasn’t contributing significant light to the picture. I thought it just didn’t have enough output (even at its highest setting), and was ready to write it off as a loss.

But I remembered that a camera has a “maximum flash sync speed”: if the shutter curtains are moving too fast, the flash shuts off before the whole sensor is exposed. I didn’t think that would matter with this light because it isn’t a “flash”, it’s on for 1/2s, so the shutter speed could be anything. But I Googled it anyway, and found out about something called “FP mode”.

FP stands for Focal Plane shutter, meaning one that sweeps a gap between 2 curtains over the sensor, creating that potential problem with flash sync. In FP mode the flash is triggered in multiple short bursts of lower intensity, as that gap makes its quick trip across the sensor. FP mode shouldn’t have any effect on this LED light – it can’t be controlled in this way, and compared to a 1/1000s shutter, it stays on for eternity. But I tried it anyway. It worked! The LEDs illuminated the whole image, enough to make a difference in the aperture I could use.

Dragonfly - macro photo with ring flash

But why did FP mode work? I suspect in normal flash photography, where the light has a very short duration (like 1/10,000th of a second) the camera tries to trigger the flash in the middle of the shutter open time. That’s apparently too late for this LED device, at fast shutter speeds. But in FP mode the camera starts firing the flash right away – and the first time it triggers this LED light, it comes on and stays on for 1/2s – so it’s on by the time the shutter curtains start moving that gap over the sensor.

Hoverfly - macro photo with ring flash
This handsome fellow is one of the many species of Hoverfly.

The bottom line is – a cheap LED ring flash can work fine for insects at high shutter speeds, at least with the Z6, in FP flash sync mode.

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