The characteristic-curve record

One strip, three sheets, in the order the work happens. SN-1 is filled before the film is developed and carries the things that cannot be reconstructed afterwards: the head height, the aperture, the three illuminance readings and the falloff they give, the wedge’s part number and which way up it went. SN-2 is the twenty-one readings, plus the masked patch and the control strip, which are rows and not footnotes. SN-3 is what the plotted curve says.

Print SN-1 before the session and take it to the enlarger. The step-wedge lab is the page that asks for every field on it, and the assignment before it is where the arithmetic on SN-3 was rehearsed on data that could not bite back.

!Three figures the sheet asks for and prints no limit against

The reading spread, the illumination falloff and the agreement with a published curve all have fields on SN-3, and none of them has an acceptance limit printed beside it. That is deliberate: this course has established none, and a limit nobody has earned is worse on a bench sheet than a blank, because a printed number gets believed.

What the sheet does insist on is that the figures are written down, so that the smallest difference you are entitled to call real is a measurement rather than a feeling. The last field on SN-3 asks for the whole finding in one sentence — the figure, the criterion that produced it, and its uncertainty — because that sentence is the deliverable and everything above it is working.

Printing, versions, and why nothing on a sheet explains anything: see printable worksheets.

Pure Silver · The characteristic-curve record

SN-1

The strip — what made it

One strip. Everything on this sheet is written before the film is developed.

Sessionbefore

Date

Byinitials

Notebook page

Strip notch code

Exposure batch this strip belongs to

Room temperature°C

The light sourcebefore

Enlarger, make and head

Head typecondenser / diffusion / cold cathode / other

Lamp type and power

Minutes lit before the first exposure

Head height, measuredmm

Lens and aperture

Illuminance at the centrelx

At one end of the wedgelx

At the other endlx

Falloff in wedge stepslog10(centre/edge) ÷ 0.15

Exposure time givens

Log exposure to bare film, if measuredleave blank and work relative

The wedgebefore

Part number

Calibrated part?no / yes

Density of step 1

Nominal increment

Emulsion to emulsion?yes / no

Damage or marks noted, and on which steps

Film and processas you go

Film and format

Emulsion batch

Developer and formula version

Dilution and volume

Timemm:ss

Temperature at start°C

Middle°C

End°C

Agitation script, in words

Control strip in the same tank?yes / no

Fixer, dilution, clearing time, fixing time

Pure Silver · The characteristic-curve recordSN-1 · v1.1 · sheet 1 of 4puresilver.runbook.academy/worksheets/curve-plotting/

Pure Silver · The characteristic-curve record

SN-2

The twenty-one steps

One strip, read once by each method. Fill the log H column first, from the wedge.

Readingsafter

Step	Wedge Dnominal	Log HlogH0 − wedge D	Density, method 1	Density, method 2	Notes
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
masked
control

Pure Silver · The characteristic-curve recordSN-2 · v1.1 · sheet 2 of 4puresilver.runbook.academy/worksheets/curve-plotting/

Pure Silver · The characteristic-curve record

SN-3

The curve — what it says

Read off the plotted curve. Every figure carries the construction that produced it.

Reading method and its resolutionafter

Method 1lux meter / spot meter / visual match / scanner / densitometer

Method 2lux meter / spot meter / visual match / scanner / densitometer / none

Repeat spread at a thin stepD, from five readings

Repeat spread at a dense stepD, from five readings

Steps excluded at the thin end

Steps excluded at the dense end

Base, speed and the development conditionafter

Base plus fog from the control stripD0

Masked patch on this stripD

Criterion densityD0 + 0.10

Log H at the criterion point

Density 1.30 log units further along

Rise over 1.30wanted 0.80 ± 0.05

Development at the criterion?yes / under / over

Speed, if the condition holds800 ÷ antilog(log H)

Contrast, by three constructionsafter

Trial	Trial ΔD	D1 = D0 + 0.1ΔD	D2 = D0 + 1.1ΔD	Run measured	Run required√(4 − ΔD²)	Verdict
1
2
3
4

Contrast indexΔD ÷ √(4 − ΔD²)

Gamma, and between which two points

Average gradient, and between which two densities

What it is forafter

Density range of the readable run

Subject range this suitsstops

Paper range figure it implies

Filter or grade

Target contrast index next time

Development time to trymin, off your time-CI plot

Relative or absolute?relative to a nominal wedge / absolute

The one sentence: the figure, its criterion, and its uncertainty

Pure Silver · The characteristic-curve recordSN-3 · v1.1 · sheet 3 of 4puresilver.runbook.academy/worksheets/curve-plotting/

Pure Silver · The characteristic-curve record

CP-4

Reflection-density measurements

One instrument or material, one dated measurement session.

Conditions and traceabilitybefore

Date and session id

Instrument or sample id

Reference and its uncertainty

Geometry and light source

Criterion declared before measurement

Environment and temperature

Measurementsas you go

Patch / step	Relative logH	Reflectance / reference	Reflection density	Dry / viewing state

Decisionafter

Observed spread, uncertainty and exclusions

Pass against the declared criterion, or action required

Pure Silver · The characteristic-curve recordCP-4 · v1.1 · sheet 4 of 4puresilver.runbook.academy/worksheets/curve-plotting/

Where the fields come from

Every field on these sheets is one a written page of the course asks you to record. Those pages are linked here, and the build fails if one of them stops existing.

• Part 13 — step wedge exposure seriesData to record: the light-source block with its measured uniformity, the wedge block, the process block, one row per step, and the day's uncertainties.
• Part 13 — interpreting density dataThe table of base plus fog, criterion point, relative speed, the rise over 1.30, gamma, average gradient and contrast index for each condition.
• Part 13 — gamma contrast index and average gradientThe contrast index by the course's arithmetic construction: the trial density differences, the run each gives, and the run the condition requires.
• Part 13 — film speed and exposure indexThe criterion point at 0.10 above base plus fog, the density 1.30 further along, and whether the development qualifies before a speed is quoted.
• Part 9 — preparing standard test negativesThe notch code, the exposure batch it belongs to, and the masked patch read against clear fixed film.
• Part 13 — paper sensitometryRecords the paper response with its reflection geometry, dry state and exposure scale.

What these sheets do not carry

• There is no column for an absolute log exposure in lux-seconds, because a home chain rarely has one: the sheet records the log exposure the enlarger delivered to bare film if you measured it, and otherwise the relative scale, and asks you to say which. Every figure computed from the relative scale is a relative figure.
• No acceptance limit is printed for the reading spread, the illumination falloff or the agreement with a published curve. The course has established none, and a limit nobody has earned is worse on a sheet than a blank.