Lumis

The hardest part of darkroom printing isn't developing — it's metering.

Every hand-printed silver gelatin photograph lives or dies by its exposure time. The traditional approach: cut test strips, guess based on experience, print and repeat. Each sheet of paper costs money, each retry costs time. The Zone System gives you a framework for precise tonal control, but on the enlarger, you need more than theory — you need measurement.

Lumis brings metering to the enlarger. One probe, one app, and you know exactly where every zone will fall before you press the timer.

App

Four tabs covering the complete darkroom metering workflow: Reading for live metering, Spots for multi-point management, Expose for exposure calculation, Cal for paper calibration. Real-time Bluetooth connection to the probe — every operation without leaving the enlarger.

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1. Meter

Place the probe on the projected image and measure key points. The high-dynamic-range sensor reads illuminance in real time, accurately quantifying everything from deep shadow to pure highlight. Once you set a reference reading, each spot is automatically converted to a relative f-stop difference.

2. Assign Zones

Stored spots are collected on the Spots page. Each point shows its illuminance and f-stop offset from the reference — you simply assign it to Zone 0–X. The system automatically calculates the overall density range and recommends a paper grade, turning Zone System decisions from intuition into measurement.

3. Calculate Exposure

Based on your paper's calibration curve, Lumis calculates the exact exposure time. The Zone Map makes it visual — every spot's zone placement at a glance. F-stop fine-tuning and split-grade printing are built in, with Grade 00 (soft) and Grade 5 (hard) times computed together.

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Calibration

Quick-Cal lets you build a paper calibration curve with minimal test prints — make one standard exposure, compare the result, tap a few buttons, and calibration is done.

Design

Enclosure designed in Fusion, 3D printed. Form follows function — flat base for stable contact with the projected image, angled grip for single-hand operation, calibrated sensor aperture for consistent readings.

Specifications

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