• Director of Photography / Cinematographer: Plan camera and lighting packages before the shoot. Know your T-stops, required lux values and power draw before renting gear.
• Gaffer / Chief Lighting Technician: Receive a Shoot Plan PDF with every fixture, its position, power setting and circuit assignment. No back-of-the-envelope math required.
• Photographer: Calculate required strobe or continuous power for studio or location shoots. Switch between ISO, shutter angle/speed and aperture (T-stop) modes.
• Camera Assistant / DIT: Verify exposure settings before rolling. Cross-reference LightCalc's required illuminance against your incident meter reading.
• Students & Self-learners: Understand the relationship between ISO, shutter, aperture and light intensity through interactive exploration — not just formulas.

Select a preset ambient environment from the dropdown. Each scenario corresponds to a typical measured illuminance range for that type of environment. Examples include:

The read-only field below the scenario dropdown shows the lux or foot-candle value associated with your selected scenario. This is for reference — it confirms what illuminance value the calculation is using as the ambient baseline.

Tick the Custom checkbox to override the preset scenario with your own value. This is particularly useful when you have measured the ambient on location with a handheld incident light meter. Type in your measured lux or fc value and LightCalc immediately incorporates it.

Ambient illuminance feeds into both the Subject Illuminance total (ambient + keylight) and the Ambient to Key delta (how many stops the background appears over or under the camera's exposure target). Raising ambient brings the background up, reducing the lighting ratio between subject and environment.

Select the type of subject you are exposing for. Each option maps to a typical reflectance value:

The read-only field shows the reflectance percentage of the selected subject type. This confirms the value being used in the calculation.

Reflectance directly scales the Required Illuminance. A subject with 36% reflectance (twice that of an 18% grey card) needs only half the illuminance to achieve the same exposure. Conversely, a black subject at 6% needs three times as much light as a grey card to appear correctly exposed at the same camera settings.

LightCalc supports two ways of expressing the shutter setting, switchable in Settings → Shutter Type:

• Angle mode: Shows Frame Rate + Shutter Angle fields. Shutter speed is derived automatically: exposure time = angle / (360 × fps).
• Speed mode: Shows a direct Shutter Speed dropdown. Use this if your camera displays speed rather than angle or for still photography.

At 24 fps with a 180° shutter: 180 ÷ (360 × 24) = 1/48 second.

Every change in camera settings shifts the Required Illuminance up or down:

• +1 stop ISO (e.g. 800 → 1600) → Required illuminance halves
• Wider T-stop (e.g. T2.8 → T2.0) → Required illuminance drops by ~2 stops
• Doubling frame rate (24 → 48 fps at same angle) → Required illuminance doubles
• Adding ND 0.6 (2 stops) → Required illuminance × 4

Choose your lighting unit from the fixture library. The library contains hundreds of fixtures from manufacturers including ARRI, Aputure, Litepanels, Mole-Richardson, Kino Flo, Godox and many others — each with their manufacturer-published lux/fc output at a specified reference distance.

Fixtures are displayed as Make + Model. Once selected, LightCalc uses the fixture's photometric data to calculate how much illuminance it delivers at your specified subject distance.

A modifier is any light shaping accessory attached to the fixture: softbox, octabank, fresnel lens, parabolic reflector, bare bulb and so on. Modifiers change both the quality of light (hard vs soft, directional vs diffuse) and the total output intensity.

Each fixture/modifier combination has its own measured lux output. Selecting a fresnel modifier on a fixture might deliver more punch than the same fixture with a softbox, because a fresnel focuses and projects the light more efficiently.

How many identical units of the selected fixture are in the rig. Multiple heads multiply the total output proportionally. Two identical fixtures produce twice the illuminance of one.

Controls the power level of the fixture, from 0% (off) to 100% (full power). Dimming affects both light output and power consumption proportionally. At 50% dimming, the fixture produces approximately half the illuminance and draws approximately half the wattage.

Colour correction or effect gels placed over the fixture. Gels transmit a specific percentage of light — a heavy CTO or deep blue gel may lose 1–2 stops of output. LightCalc applies the gel's transmission factor to the fixture output so your exposure calculation stays accurate even when correcting colour temperature or adding colour effects.

The vertical height of the fixture above the subject. When a fixture is raised (for example, a top light at 3 metres height aimed down at a subject), the actual source-to-subject distance is longer than the horizontal floor distance. LightCalc computes the true 3D distance using the Pythagorean theorem and displays it as "actual distance" next to the distance slider.

This matters significantly for the inverse square law calculation. A fixture 3 metres away horizontally but 3 metres high is actually 4.24 metres from the subject — a difference that translates to roughly 1 full stop less illuminance.

Toggle this on if the fixture is powered by a battery rather than a mains circuit. Battery-powered fixtures are excluded from power draw and circuit load calculations, since they don't consume grid power.

When enabled, the keylight is treated as part of the ambient environment rather than a directional key source. The distance slider is disabled and the fixture's output is incorporated into the ambient level instead. This models scenarios where you are using HMIs or LEDs to boost the general ambient of an exterior or large interior space, rather than to key a specific subject.

The filter tool (funnel icon) lets you narrow the fixture library by:

• Minimum illuminance: Only show fixtures that can achieve your Required Illuminance at the current distance
• Fixture type: LED, HMI, Tungsten, Fluorescent, etc.
• Max wattage: Filter to fixtures within a power budget

The active filter is indicated by a highlight on the funnel icon in the sidebar. Applied filters persist until cleared.

Compare up to three different fixtures side by side. When comparison mode is active, a second (and optionally third) fixture column appears with its own fixture, modifier, gel and dimming controls. Output metrics for each are shown alongside each other so you can evaluate alternatives before committing to a rental.

Beyond the primary keylight, you can add supplementary fixtures to the rig: fill lights, hair lights, practicals, rim lights and so on. Each additional fixture has its own full set of controls:

• Name: Custom label for this fixture (e.g. "Fill", "Hair Light", "Practical 1")
• Fixture + Modifier: Same library as the primary keylight
• Count / Dimming / Gel: Same controls as primary keylight
• Lamp Height: Vertical height for this fixture
• Distance: Managed via the Distance slider — select the fixture's pill to control it
• Diffusion: Each additional fixture has its own independent diffusion settings
• Battery Powered: Marks fixture off grid
• Circuit Assignment: Assigns this fixture to one of your defined circuits (if circuits are set up)

Diffusion stop loss is logarithmic, just like all photographic exposure measurements:

If you use a proprietary or unusual diffusion material not in the library, Plus users can create custom entries. Click the manage button (+ icon) in the Diffusion form to open the Custom Diffusions manager. Enter the material name and its measured stop loss. Your custom materials appear in the diffusion dropdown alongside the built-in library.

When any diffusion is active (either the primary material is not set to "No Diffusion" or double diffusion is on), the Diffusion icon in the sidebar shows a small checkmark badge. This is a quick visual reminder that diffusion loss is factored into your current calculation.

In the Scene Editor (Plus only), diffusion elements are visible as translucent panels in the bird's-eye view. You can drag them along the keylight-to-subject axis to position them visually. Their position in the editor is cosmetic only — the diffusion stop loss calculation applies regardless of position.

Drag the slider to set the distance. The track fills with a colour corresponding to the selected fixture (yellow for the primary keylight, other colours for additional fixtures). The numeric value updates live as you drag.

You can also type directly into the large numeric input below the slider for precise values. The input accepts decimal values to one decimal place (e.g. 3.5 m or 11.5 ft).

Distance is displayed in metres (m) or feet (ft) depending on your setting in Settings → Unit of Length. When you switch units, all distance values throughout the app (including lamp heights and additional fixture distances) are converted automatically.

Click the range button in the top-right corner of the Distance card (shows the current range, e.g. "0–150m") to toggle between standard and extended ranges. Extended range is useful for:

• Large area lighting (warehouses, outdoor concerts, stadium events)
• Modelling the sun as an ambient source at extreme distance
• Long-throw fixtures like aircraft landing lights or stadium fixtures

When the lamp height field in the Keylight form has a value greater than zero, the Distance card shows an "actual:" figure below the main distance display. This is the true 3D distance from the fixture to the subject, calculated via the Pythagorean theorem from horizontal distance and vertical height.

The inverse square law calculation always uses the actual distance, not the horizontal distance. This means that raising a fixture reduces its effective output, which is accounted for automatically.

When additional fixtures are present in your rig, the Distance card shows a row of selector pills at the top — one for the primary keylight (yellow) and one per additional fixture (each in its own colour). Click a pill to switch the slider and numeric input to control that fixture's distance. Each fixture maintains its own independent distance value.

Click Add Circuit to create a new circuit. You can define up to 5 circuits per project. Each circuit gets a color and a name you can customise.

Each additional fixture (in the Keylight form) has a Circuit dropdown that assigns it to one of your defined circuits. Fixtures not assigned explicitly default to the first defined circuit. Battery-powered fixtures are automatically excluded from all circuit calculations.

The output area shows circuit load metrics colour-coded by safety level:

• ✓ Green (<70%) — Safe. Comfortable headroom for fluctuations and cable losses.
• ⚡ Amber (70–80%) — Near limit. Approaching industry-standard maximum. Consider redistributing load.
• ⚠ Red (>80%) — Overloaded. Risk of tripping the circuit breaker. Reduce load before going to set.

A toggle button at the top of the output area switches between two display modes:

• Illuminance mode: Shows all values in lux (lx) or foot-candles (fc). Use this when you have a light meter and want to match readings on set.
• T-Stop mode: Converts all illuminance values to equivalent T-stop readings. Use this when you think in aperture stops rather than photometric units.

Plus subscribers with at least one circuit defined also see:

• Power Draw (W): Total electrical wattage consumed by all non-battery fixtures at current dimming levels.
• Fixture Count: Total number of fixture heads in the rig (keylight × quantity + all additional fixtures × their quantities).
• Circuit Load (%): The busiest circuit's load as a percentage of its rated capacity. Colour-coded: green < 70%, amber 70–80%, red > 80%.
• Amps Drawn (A): Current draw in amperes at the configured supply voltage, calculated per circuit.

The six core metrics form a complete narrative of your exposure scenario. Here is how to read them together:

On the dashboard, a tab row appears at the top for Plus users: Dashboard and Scene View. Click Scene View to open the editor. All input forms and output metrics still apply — Scene View is a visual layer on top of the same calculation engine.

The keylight node is a draggable icon on the canvas. Drag it anywhere to reposition it relative to the fixed subject position. As you drag, the Euclidean distance from fixture to subject is computed and immediately reflected in the Distance slider — and the Subject Illuminance metric updates accordingly. This makes distance exploration very intuitive: just drag closer or further and watch the numbers change.

A triangular light cone emanates from the keylight node, oriented toward the subject. The width of the cone is derived from the modifier's beam angle. A narrow fresnel produces a tight, focused cone; a large softbox produces a wide, even cone. The cone is purely illustrative but helps communicate the fixture's coverage intent.

When diffusion is active, a translucent panel appears between the keylight and subject on the canvas. You can drag it along the keylight-to-subject axis to position it at any fractional distance. This is a visual positioning tool — the photometric calculation uses the stop loss value from the Diffusion form regardless of panel position.

Each additional fixture appears as its own draggable node on the canvas, coloured to match the fixture's colour indicator in the dashboard. Drag any fixture to update its distance interactively. Click a fixture node to open a mini popup card with its key settings (power, modifier, gel, lamp height) without leaving the scene view.

Activate the ruler tool to measure distances between any two points on the canvas. Click a start point and end point; a measurement line appears with the real-world distance displayed. Useful for planning room layouts or checking clearance between fixtures.

Activate the light meter tool to check the calculated illuminance at any point in the scene — not just at the subject. Click anywhere on the canvas to see the estimated lux/fc at that location, based on the inverse square law contribution from all fixtures plus ambient. Useful for mapping light falloff and checking background exposure at different positions.

Scroll to zoom the canvas. Drag on empty canvas to pan. Right-click anywhere to access a context menu where you can add additional fixture nodes at that position. Double-click fixture nodes to edit their names inline.

Click the Save button (floppy disk icon) in the project header. If this is a new project, you will be prompted to enter a name. If the project already exists, saving updates it in place and creates a new version history entry. The save state is indicated by a cloud icon — green means synced, animated means saving in progress.

Click the folder icon to open the Load Projects modal. Your saved projects are listed with their last-modified timestamp. Click a project to load it — all current state is replaced with the saved state. If you have unsaved changes, LightCalc prompts you to confirm before overwriting.

Click the new project button (+ page icon) to start fresh. LightCalc resets all inputs to defaults. If you have an active unsaved project, a confirmation dialog appears first.

From the save menu you can duplicate the current project — this creates a copy with "Copy of …" as the name, which you can then rename and modify independently.

Click the Looks button (layers/stack icon) in the project header to open the Looks panel. Click Save Current as Look, give it a name (e.g. "Day Int – Wide", "Night Int – Close Up") and LightCalc saves the current state as a Look.

In the Looks panel, click any Look to load it. The active Look name is shown in the header's Look indicator pill. If you are currently viewing the "Day Int" look, that label appears in the header. Switching Looks replaces all current input values — camera, keylight, diffusion, distance, ambient and subject all update to match the Look.

When a Look is active and you change values, the Look pill in the header shows a "save" indicator. Click it to update the current Look with your changes. Or switch to another Look to discard the changes to the current one.

A small coloured pill in the project header shows the currently active Look name. If no Look is active, the pill is hidden. Clicking the pill opens the Looks modal directly.

The history navigation arrows in the project header (← →) step through your save history. The left arrow moves to an older entry; the right arrow moves to a newer entry (back toward the current state). The entry timestamp is shown. The left arrow is disabled when you are already at the oldest saved entry; the right arrow is disabled at the current (live) state.

• FreeFree users: history is saved but not browseable
• ProPro users: 5 history entries per project
• PlusPlus users: 50 history entries per project

Click the history button (clock icon) to open the full History modal, which shows a list of all saved entries with timestamps and project names. Click any entry to jump directly to that state. From the modal you can also restore the entry as the current project.

The Dashboard PDF is a technical calculation report — a record of your current settings and output metrics. It includes:

• Project name and export date
• Three hero boxes: T-stop, ISO, Required Illuminance
• Camera detail row: frame rate, shutter angle, ND, EV offset
• Scene row: subject type, reflectance, ambient scenario and value
• Key distance
• Diffusion row: primary and secondary material with stop losses
• Full gear list table: role, fixture, modifier, count, power %, gel, distance
• Six output metric pills: Required Illuminance, Subject to Key, Subject Illuminance, Subject to Ambient, Ambient to Key, Ambient Illuminance

Filename: Dashboard-{ProjectName}-{Date}.pdf

The Shoot Plan is a crew-ready document designed to be handed directly to your gaffer, production designer or client. It contains everything needed to execute the lighting setup without requiring LightCalc itself. It includes:

• Scene diagram (bird's-eye canvas image, if Scene Editor has been used)
• Project name, date and LightCalc branding
• Three hero boxes: T-stop, ISO, Required Illuminance
• Camera detail: frame rate, shutter, ND, EV offset
• Scene detail: subject type, ambient illuminance and scenario
• Exposure detail: subject illuminance, subject-to-key stops, ambient-to-key stops
• Full gear list table: role, fixture, modifier, count, power %, gel, distance, wattage, circuit assignment
• Total power draw in watts
• Circuits section (if any circuits are defined): name, voltage, amperage, load W, load %
• Crew Notes section (if notes are entered)
• 'Generated by LightCalc.io' footer — every recipient sees the tool name

Filename: ShootPlan-{ProjectName}-{Date}.pdf

The Crew Notes field appears at the bottom of the Input Area (all tabs) as a text area. Type any free-form text: location address, call time, gaffer phone number, grip equipment notes, access restrictions, special requirements. This field is saved with the project and exported in the Shoot Plan PDF under the "Crew Notes" section.

From the Export menu (chevron in the project header), click Publish. This makes the project publicly accessible. A "Copy Share Link" option appears immediately — click it to copy the viewer URL to your clipboard. You can share this link via email, Slack, iMessage or any other channel.

From the same Export menu, click Make Private to revoke public access. The shared link stops working immediately.

The Viewer is a read-only version of the dashboard, accessible without an account at lightcalc.io/view/[id]. It shows all the same output metrics as the full dashboard but without any editable controls. Viewers can see:

• All six output metric cards (Required Illuminance, Subject to Key, etc.)
• All input settings (read-only): ambient, subject, camera, keylight, diffusion, distance
• Looks — viewers can browse all saved Looks in the project by clicking the Look pills
• Scene diagram (if the scene editor data is embedded)

Your profile is accessible from the user avatar at the bottom of the sidebar. Click it to expand the account panel, then click Profile to open the Profile modal. From there you can:

• Display Name: Your name as shown in the app, distinct from your login email.
• Profile Photo Plus: Upload and crop a profile image using the built-in crop tool.
• Account & Subscription: Shows your current tier (Free, Pro, Plus) with an upgrade button if applicable. Plus users see a Manage Subscription link to the Stripe portal for billing or cancellation.

• All six input forms: ambient, subject, camera, keylight, diffusion, distance
• All output metric calculations (runs entirely in the browser)
• Scene Editor (Plus, if assets were cached while online)
• Viewing previously loaded project data
• Looks (if the project was loaded before going offline)

• Saving or loading projects (requires Supabase cloud sync)
• Logging in or creating an account
• Sharing / publishing a project
• Loading the fixture library if not yet cached