Exposure Bracketing / HDR Stops Planner

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

t4-252

Ledger rows

1

No ledger note is attached.

Review findings

The core exposure-duration formula is mathematically correct, but the instrument cannot be verified as fully specified until the frame-indexing convention, duration-versus-reciprocal input representation, frame-count constraints, and camera rounding behavior are defined.

Formula and scope findings

• The multiplier formula base*2^(n*stopStep) is correct for exposure duration in seconds: each positive stop doubles the duration and each negative stop halves it.
• The specification does not define how n is assigned from number of frames. To produce brackets around the base exposure, n must be explicitly centered, such as -(frames-1)/2 through +(frames-1)/2.
• Even frame counts require fractional n values under centered indexing; this is valid mathematically but must be specified.
• The formula assumes shutter speed means exposure duration. If shutter speed is represented as the denominator in notation such as 1/125, applying the formula directly reverses the intended direction.
• The specification does not state whether the base exposure must be included, whether frames must be a positive integer, or whether one-frame and zero-stop-step requests are allowed.

Unit assumptions

• base is an exposure duration, not a reciprocal shutter-speed denominator; all shutter durations must use one consistent unit.
• The test vectors use seconds or milliseconds consistently within each vector; multiplying by a dimensionless stop factor preserves that unit.
• A one-stop increase means multiplying exposure duration by 2; a one-stop decrease means multiplying by 1/2.
• The vectors assume centered n values ordered from darkest/shortest exposure to brightest/longest exposure.

Boundary hardening

BREAK_CLAIMED · SELF_FLAGGED

The extreme valid-number input produces a non-finite Infinity output, and the specification does not define validation or rejection behavior. The unspecified frame-index and shutter-direction conventions can also produce reversed or differently centered bracket lists.

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": {
    "base_seconds": 0.008,
    "number_of_frames": 3,
    "stop_step": 1,
    "n_indices": [
      -1,
      0,
      1
    ]
  },
  "expected_outputs": {
    "shutter_seconds": [
      0.004,
      0.008,
      0.016
    ]
  },
  "working": "For n=-1: 0.008*2^(-1*1)=0.008*(1/2)=0.004 s. For n=0: 0.008*2^(0*1)=0.008*1=0.008 s. For n=1: 0.008*2^(1*1)=0.008*2=0.016 s."
}

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