Flash Power

Set up your camera trap in daylight, measure the distance from flash to subject, and get a recommended power setting for the night-time exposure — without waiting until dark to take test shots.

The problem

With a camera trap, you often set everything up long before the animal appears.

You choose the camera position, place your flashes, aim the sensor, compose for a trail or clearing, and then leave the setup to work on its own. If the photograph will happen at night, the flash exposure matters — but in daylight, you cannot easily preview what that flash lighting will look like.

You can come back after dark and test it properly, but that is not always practical. Sometimes the location is remote. Sometimes you want to minimise disturbance. Sometimes you simply need to set the trap, walk away, and trust that the exposure will be close.

Flash Power was built for that moment.

What it does

Flash Power calculates the manual flash setting for a known distance, aperture and ISO.

Hold your phone near the flash, measure the distance to the subject area, enter your camera settings, and the app gives you a recommended flash power — from full power down to 1/128, with ⅓-stop precision.

It will not tell you whether the lighting is beautiful. You still need to choose the angle, height and direction of your flashes. But it gives you a solid starting point for exposure, so you are not relying entirely on guesswork.

Built for camera trappers

Flash Power is especially useful when setting up DSLR or mirrorless camera traps with off-camera manual flash.

Use it when you know where the animal is likely to pass: a trail, burrow entrance, waterhole, log, bait-free scent mark, or any fixed subject zone. Measure from each flash to the subject area, set your aperture and ISO, and dial in the recommended power before leaving the camera trap in place.

It is designed for the kind of setup where the subject distance is predictable, but the photograph may not happen until hours or days later.

How it works

Flash Power uses the standard guide number formula and the inverse square law to estimate flash exposure.

The app takes into account:

flash-to-subject distance
aperture
ISO
flash zoom position
the guide number of the selected flash

It then converts that into a practical manual flash power setting.

Distance measurement

On LiDAR-equipped iPhone Pro models, Flash Power can measure distance directly.

On other iPhones, it can use ARKit surface detection, or you can enter a distance manually if you have measured it separately. Manual entry is often useful in the field, especially if you are using a tape measure, laser rangefinder, or known setup distance.

Flash support

Flash Power includes preconfigured profiles for Camtraptions flashes, so you do not need to look up guide numbers before using them.

It also works with other manual flashes. You can create a custom flash profile by entering the flash’s guide number and zoom behaviour, then use the app to calculate power settings in the same way.

What it is useful for

Camera-trap flash setup
Night-time wildlife photography setups
Macro photography with fixed subject distances
Any manual flash situation where you know the flash-to-subject distance
Getting a reliable starting exposure without repeated test shots

What it is not

Flash Power is not a substitute for good lighting judgement.

It cannot decide where to place a flash, whether the angle is flattering, or how the scene will feel. It also cannot account for every real-world variable: modifiers, bounce, vegetation, reflective backgrounds, dark fur, pale fur, mist, rain, dust and all the other things that make field photography interesting.

But if you need a practical flash power estimate before the subject arrives, it gives you a much better starting point than guessing.