Exposure Triangle / EV Calculator

Inspectable records

Ledger state

The current ledger marks this instrument verified clean within the source-bound verification corpus.

Area

Audio, Music, Photography & Color

Tranche

tranche-4

Evidence ID

t4-157

Ledger rows

1

No ledger note is attached.

Review findings

The core EV100 calculation and the stated ISO-adjustment convention are correct under the listed assumptions. Review is required because EV versus EV100 labeling is ambiguous and the claimed equivalent aperture/shutter/ISO list has no generation formula, supported ranges, or definition of equivalence.

Formula and scope findings

• EV=log2(N²/t) is the standard EV100 formula only when N is the dimensionless f-number and t is shutter time in seconds; the output should be explicitly labeled EV100 rather than generic EV.
• EV=EV100+log2(ISO/100) is a standard ISO-adjusted EV convention, but the specification does not define whether its EV output means EV100 or EV at the selected ISO.
• No formula or rule is provided for generating the claimed list of equivalent aperture/shutter/ISO combinations. At fixed ISO, equivalent settings satisfy N1²/t1=N2²/t2; when ISO changes, equal exposure requires ISO1·t1/N1²=ISO2·t2/N2².
• The equivalent-combination output is mathematically non-finite unless the product is bounded to camera-available aperture, shutter-speed, and ISO steps.

Unit assumptions

• N is a dimensionless positive f-number, such as 2, 2.8, or 4; it is not an aperture diameter in millimeters.
• t must be a positive shutter duration in seconds. A value such as 250 ms must be converted to 0.25 seconds before applying the formula.
• ISO is a positive numeric sensitivity rating, with ISO 100 as the normalization reference.
• log2 denotes base-2 logarithm.
• The ISO-adjusted formula assumes the conventional linear ISO relationship and the convention EV_ISO=EV100+log2(ISO/100).

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

A zero shutter-speed input makes the core EV expression undefined and must be rejected. The specification also has no true formula branch, and ambiguous shutter-speed notation can produce a 13.9315685690-stop discrepancy if interpreted incorrectly.

Errata and corrections

No applied erratum is attached to this unique-name record.

Inspectable example

4 review vectors are recorded. One source-bound sample is shown below.

{
  "inputs": {
    "f_number": 2,
    "shutter_speed_seconds": 0.25,
    "ISO": 100
  },
  "expected_outputs": {
    "EV100": 4,
    "EV_at_ISO": 4,
    "equivalent_exposure_examples": [
      {
        "f_number": 4,
        "shutter_speed_seconds": 1,
        "ISO": 100
      }
    ]
  },
  "working": "N²=2²=4. t=0.25 s. N²/t=4/0.25=16. EV100=log2(16)=4. ISO adjustment: log2(100/100)=log2(1)=0. EV_at_ISO=4+0=4. Equivalent example: 4²/1=16, matching the original 2²/0.25=16."
}

Related workflows

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json · VERIFIED_CLEAN
• evidence-tranche4/tranche4-results.json
• BOUNDARY_HAZARD_CATALOG.json