# Lumen Forge — Field exposure meter

> Field exposure meter (iPhone/iPad app by Robert Corbin.)

- Source: https://appshunter.io/ios/app/lumen-forge/id6771018028 (this page in markdown: same URL + `.md`)
- Developer: [Robert Corbin](https://appshunter.io/developer/1890247992)
- Category: Photo & Video
- Price: $3.99
- Age rating: 4+
- Requires: iOS 17.0 · 27 MB
- Languages: American English
- Released: 2026-05-20
- Data updated: 2026-09-04
- User reviews in markdown: https://appshunter.io/ios/app/lumen-forge/id6771018028/reviews.md

## What is Lumen Forge?

Lumen Forge is a field exposure workbench for photographers, cinematographers, gaffers, students, and anyone who wants reliable light and exposure math close at hand.

Use the camera-based meter to read scene luminance and color temperature, then move directly into exposure planning, ND selection, flash guide-number math, zone-system notes, saved lighting recipes, or the new Field Pack.

Core tools:
- Live camera-based light meter
- Lux, foot-candle, EV, ISO, shutter, and aperture readouts
- Exposure triangle solver with equivalent exposure ladders
- Color-temperature reference swatches for common lighting conditions
- Zone-system histogram with shadow and highlight warnings
- ND filter calculator for daylight long-exposure planning
- Flash guide-number math with ISO scaling
- Lighting recipe notebook with modifier, subject, and location notes
- Side-by-side recipe compare
- B&W filter factor calculator with Kelvin interpolation
- Hyperfocal, cine shutter, sunny f/16, macro, polarizer, and star-trail helpers
- Film reciprocity correction and AEB bracketing planner
- Field Pack with readiness scoring, support/gels/ND/bracket guidance, copyable shot brief, and ten offline reference sheets

Lumen Forge keeps the workflow focused: meter the light, compare choices, save a useful note, and get back to shooting.

Lighting recipes and app settings stay on the device. Camera access is used only for the live meter and color-temperature features.


## Version history (last 5 releases)

### 2.2 — 2026-08-20

Adds Field Pack with exposure-readiness scoring, support, gel, ND, and bracket guidance, a copyable shot brief, and ten offline reference sheets for field lighting decisions.

### 2.1 — 2026-06-30

Version 2.1 adds Field Pack: a shot-brief planner with readiness scoring, ND/gels/bracket/support recommendations, copyable production notes, and ten high-resolution offline reference sheets for exposure, lighting ratios, Zone System placement, ND, gels and mired correction, cinema shutter angle, macro bellows, film reciprocity, location scouting, and keeper-frame prep.

Also includes updated screenshots and metadata to show the current app UI and Field Pack workflow.

### 2.0 — 2026-06-24

Lumen Forge 2.0 — eight new pro tools join the light meter, still 100% offline.

• Lighting Ratio: stops or apertures to a key:fill ratio, ASC ratio, and contrast band.
• Inverse Square: a falloff curve, remaining-light percentage, and the aperture compensation to hold exposure.
• Bellows Factor for macro: extension or magnification to a corrected f-number and shutter.
• Gel Balance: Kelvin to mired with the closest CTO/CTB gel recommendation.
• Dynamic Range (SBR): add spot readings for a stops measurement, a zone-placement strip, and a grad-ND / bracket plan.
• Flash Balance, Grey-Card Compensation, and an EV↔lux reference chart.

All APEX and optics math is computed on-device and oracle-verified. No account, no network — everything stays on your device.

### 1.3 — 2026-06-15

Lumen Forge - What's New

Version 1.1

B&W Filter Factor Calculator - 17 Wratten filters (yellows K2/6/9/12/15, oranges 21/22, reds 25-A/29-F/70, greens 11/13/58, blue 47, 80A conversion, UV/1A, CPL) with accurate daylight and tungsten factors sourced from Kodak B-3, the Ilford B&W Guide, and Ansel Adams' published tables. Stack up to 3 filters, interpolate factor at any Kelvin from 3200 to 5500, and pull the live meter reading for instant shutter correction. Available in Pro Hub.

Depth-of-Field Table - The Hyperfocal calculator now shows a full DoF table across every standard full-stop aperture: near limit, far limit, and total depth of field for the current focal length and subject distance. Tap any row to jump to that aperture.

Recipe Compare - Select any two saved lighting setups and compare them side-by-side: EV difference, aperture and shutter stop delta, ISO ratio, Kelvin difference, and lux difference - all at a glance.

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Version 1.0 (launch features - already shipped)

Film Reciprocity Calculator - 25 classic film stocks (Ilford, Kodak, Fuji, Foma, Rollei, ADOX). Enter your metered time; Lumen Forge applies the Schwarzschild formula to deliver the corrected exposure plus a per-film quick-reference table.

Exposure Bracketing - Plan AEB sequences before you set up. Choose 3/5/7/9 frames and step size (⅓ to 2 stops). The full bracket sequence appears with each shutter speed clearly listed.

Recipe CSV Export - Tap the share icon in Lighting Recipes to export all saved setups as a comma-separated file. Works with Numbers, Excel, and any spreadsheet app.

Pro Hub with eight calculators at launch: Hyperfocal, Cinema 180 shutter, Sunny f/16, Macro reciprocity, Polarizer, Star Trail (NPF rule), Film Reciprocity, and Bracketing.

### 1.2 — 2026-06-13

Lumen Forge 1.2 adds a Film Reciprocity calculator for 25 classic stocks (Ilford, Kodak, Fuji, Foma, Rollei, ADOX) using the Schwarzschild formula, an exposure Bracketing planner (3/5/7/9 frames, ⅓–2 stop steps), and CSV export of your lighting recipes. Fully offline — no account, no ads, no tracking.

## More apps by Robert Corbin

- [Daily Word Journey](https://appshunter.io/ios/app/daily-word-journey/id6761548266)
- [Hush Secret Text](https://appshunter.io/ios/app/hush-secret-text/id6761658175)
- [Renew Guard](https://appshunter.io/ios/app/renew-guard/id6761755447)
- [Receipt to PDF](https://appshunter.io/ios/app/receipt-to-pdf/id6761782025)
- [Route Your Pay](https://appshunter.io/ios/app/route-your-pay/id6761783719)
- [Tip Arbiter](https://appshunter.io/ios/app/tip-arbiter/id6761786879)

All apps by Robert Corbin: https://appshunter.io/developer/1890247992

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-09-04.*