Light meters have been a bit out of fashion for a while – although you’ll get my Sekonic from my cold dead hands! – but they have started to make a little bit of a comeback over the last couple of years. It’s partly due to the resurgence of film and cameras that don’t contain built-in meters but also the value that some photographers find it provides in their work. The only problem is light meters can be expensive!
Well, now there’s a new open-source incident light meter that you can build yourself for less than $50 – assuming you can find a Pi selling for RRP. It’s been created by VEEB, a group of Switzerland-based photographers who’ve taken to building their own kit. The Photon was created to provide incident light readings for shooting with Pentax Hasselblad and other old film cameras the VEEB team had that don’t have built-in light meters.
All DSLRs and mirrorless cameras have a reflective meter built in. Reflective meters work by looking at the amount of light hitting the surface you’re pointing it at and figuring out its brightness. It then gives you an aperture/shutter speed/iso combination to give that surface an adequate exposure. More advanced meters do get a little bit more complex, but that’s the very basics of how they work. These can sometimes be tripped up by overly dark or overly bright subjects, causing the meter to overexpose or underexpose the shot.
Reflective meters work a little differently. Instead of looking at the light hitting your subject, it takes an objective look at the light by reading the amount of light it sees coming from the source and hitting the meter itself. This gets you a good exposure for the amount of light available, making sure that dark subjects stay dark and bright subjects stay bright.
This DIY solution is based on a Raspberry Pi Pico, along with a tiny 128×128 OLED screen, LiPo shim, LiPo battery, rotary encode, a couple of momentary switches and a light sensor. The total cost should be less than $50, especially if you shop around. There’s a Pi shortage at the moment (even the Pi Pico), and there are a lot of people selling at extremely inflated prices. If you can’t find one close to the retail price (the Pi Pico should be around $7-10 each), then keep looking or get on a waitlist at a reputable retailer.
If you can’t justify the cost of an expensive Sekonic light meter and feel confident having a go at making your own, this is well worth looking into. The one thing this meter can’t do is meter flash. For that, you’ll still need something a little more expensive. But when it comes to ambient light, VEEB says they’ve compared their results to those of a Sekonic meter, and they are getting identical readings from both.
All of the 3D models for the case, the bill of materials and code for the Pi Pico is available to download on GitHub.