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THE FEUTEX TOOLKIT

Studio Light Contribution Ratio

Compare key-plus-fill illumination with fill alone from measured light contributions.

Photography workspace● Runs in your browser
01 Your input
02 Your result
View or copy raw result data
FormulaRatio = (key+fill)/fill; Stops = Math.log2((key+fill)/fill)

Made for real tasks

  • Compare key-plus-fill illumination with fill alone from measured light contributions.
  • Compare two scenarios by changing the inputs and rerunning the tool.
Explore step-by-step workflows →

Worked example

Inputs

Key
800 lux
Fill
200 lux

Expected results

Ratio
5 ratio
Stops
2.321928095 stops

Load the example in the workspace to reproduce these results. Display rounding does not change the underlying calculation.

How to use this tool

  1. Enter key, fill.
  2. Use consistent units shown beside each input. Run the calculation and review the assumptions below.

Try this example

{
  "key": 800,
  "fill": 200
}

Accuracy and scope

Illuminance readings use the same geometry; this is light contribution contrast, not a camera exposure recommendation.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.