How Equipment works
Lens + body + film clamps the wheels to values you can actually set.
Where to find it
Tools tab Equipment
Summary
Equipment selection: pick a lens, camera body, and film stock. The combination clamps the main wheels (aperture, shutter, ISO) so they only show values that exist on your gear.
Detail
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How it works
This is where you tell the app what gear you are shooting with: a lens, a camera body, and a film stock. The app uses that combination to clamp the main wheels (aperture, shutter, ISO) so they only show values you can actually dial in on the gear in your hand.
Lens
Pick the lens you have mounted. The lens decides how wide your aperture can open and how long the focal length is. A 50mm f/1.4 opens the wheel down to f/1.4. A slow zoom might not go faster than f/4.
Camera body
Pick the body. The body decides how fast and how slow the shutter can go. A leaf shutter caps at 1/500. A focal-plane SLR might reach 1/4000. The body also tells the app whether Bulb (long-exposure) mode is available.
Film stock
Pick the roll loaded in the camera. The film pins ISO to the box speed and tells the app about reciprocity (how the film behaves at long exposures) and latitude (how much over- or under-exposure it tolerates).
Why it matters
Without picking gear the meter can offer values that are impossible to set on your camera. With Equipment filled in, every suggestion is something you can actually shoot.