Acutance, Adjacency Effects and Compensating Development

Higgins and Jones measured the smallest density gradient a person can see across an edge and put it at 0.005 density units per micrometre. That single figure is what turns “sharp” from an adjective into a measurement: it says where an edge profile stops mattering, and therefore where you start and stop reading when you want a number for how abrupt an edge is.

This page is about the number, and about the fact that a developer can change it. The lens delivered a particular edge; the emulsion blurred it; and then, while the film sat in the tank, the chemistry put some of the edge back — sharpened it beyond anything the optics justified, by exhausting itself unevenly. Understanding how is the difference between choosing a dilution and copying one.

Acutance is a measurement, and it is not resolving power

Acutance is taken from a microdensitometer trace across a knife-edge exposure: expose half the frame and not the other half, develop, and measure density along a line crossing the boundary. The paper this course reads on the subject states the method compactly — the measure “is related to the average square gradient of the knife-edge density profile”, and the square is taken deliberately, “in order to differentiate between knife-edge exposures that are very different in shape but may have the same average value for their respective gradients”.

G(x) = dD/dx, and acutance follows the mean of G(x)²

What acutance is built from

D is density, x is position across the edge in micrometres, and G is the local gradient of the trace. Two edges can rise through the same total density over the same total distance and be quite different pictures: one a smooth ramp, the other a step with a bright and a dark line beside it. Averaging G cannot separate them. Averaging G² can, because it rewards steepness wherever it occurs. The start and stop points of the average are set by Higgins and Jones’s threshold: you begin reading where the gradient first exceeds 0.005 D/µm and stop where it falls below.

The paper names two published definitions built this way, Jones and Higgins’s acutance and Perrin’s acutance, and reports that both are “the best measures for expressing the edge curve enhancement caused by adjacency effects”.

!Sharpness, acutance and resolving power are three different words

Part IV separated resolving power from the modulation transfer function. This page adds the third member of the family, and the distinction is worth holding on to because manufacturers publish two of the three and never the one people argue about.

• Resolving power counts how fine a set of ruled lines can still be told apart, in lines per millimetre. Kodak publishes it, twice, at two test-object contrasts — 63 and 200 lines/mm for the same film — because the answer depends on the target.
• Acutance measures how abruptly density changes across one edge. It says nothing about how many lines you can separate.
• Sharpness is the subjective impression, and it tracks acutance far more closely than it tracks resolving power at normal viewing distances.

No manufacturer in this course’s corpus publishes an acutance figure for any current film. They publish resolving power and MTF curves, and they use the word “sharpness” in prose — ILFORD’s “maximum sharpness” recommendation, Kodak’s “for greater sharpness” — without attaching a number to it. So when this page says a developer raises acutance, it is naming a mechanism and a measurable quantity, not quoting a published measurement of one.

Two spread functions, and the chemical one reaches much further

Part III drew the flows at an edge and this page does not redraw them: inhibitor moves from the dense side into the thin side, fresh developer moves the other way, and the result is a density maximum on the dense side — the border effect — and a minimum on the thin side, the fringe effect. What Part III did not give is the scale of those flows, and the scale is what decides whether they are visible at all.

The model in the Optica Applicata paper carries two spread functions with a range constant each. The line spread function describes how far light scatters sideways inside the emulsion, with a constant K. The chemical spread function describes how far the development by-products travel sideways, with a constant K_c. Fitting the model to microdensitometer traces from three colour negative films, the authors report K = 15 to 20 and K_c = 90, in micrometres.

How far the light spreads, and how far the chemistry reaches

1. 1Light spread, K = 15 to 20 µm — how far the exposure itself is smeared sideways inside the layer
2. 2Chemical spread, Kc = 90 µm — how far the inhibitor and the fresh developer reach across the edge
3. 3Kodak’s granularity aperture, 48 µm — on the same scale, for orientation; nothing here is visible unaided

Values fitted by Rajkowski and Nowak to Kodak Gold colour negative films in C-41, which carry inhibitor-releasing couplers. The ratio is what this course carries forward, not the figures.

Read the ordering rather than the figures. The chemistry reaches four to six times further across the edge than the light does. That is the whole reason an adjacency effect is visible: if the chemical spread were much smaller than the optical spread, the edge enhancement would sit inside the blur and never show. It is also why the effect is a microscopic one that shows up at enlargement — 90 µm on the negative is about a millimetre in a 10× print.

⁇Whose names are on these effects, and what the course could not establish

The literature attaches two personal names to the phenomena on this page: a Mackie line for the paired light-and-dark border either side of an edge, and the Eberhard effect for the density difference between a small patch and a large one at the same exposure. Both names are in general use, and this course’s glossary carries them as aliases of adjacency effect.

The course has not read a document that establishes either attribution. The peer-reviewed source it holds uses “border effect” and “fringe effect” and names neither Mackie nor Eberhard; Eder’s history mentions an Eberhard working on spectral sensitising at the Vienna Graphische Lehr- und Versuchsanstalt from 1897, which may or may not be the same person and is certainly not the same subject. So the position is not that the sources disagree, but that the course has one set of names with a mechanism attached and a second set with no provenance it can show you.

What the course does: it teaches border and fringe effects with the mechanism, uses the popular names where a reader will meet them, and states here that the attributions are unverified. If you find the primary papers, that is a correction this course wants.

What the trace looks like when the chemistry has been at work

Density across a knife edge, with and without adjacency effects

• Continuous agitation, strong developer
• Restrained agitation, dilute developer

Show the numbers behind this plot

Two density traces are plotted against position across an edge, both crossing from a heavily exposed area on the left at density 1.30 to a lightly exposed area on the right at density 0.35. The first trace, labelled continuous agitation in a strong developer, is a smooth sigmoid: it holds at 1.30, falls through the boundary at position zero, and settles at 0.35 without overshooting at either end. The second trace, labelled restrained agitation in a dilute developer, follows the same overall drop but adds two departures. Approaching the edge from the dense side it rises above its own plateau to about 1.45 immediately before the boundary, which is the border effect. Immediately after the boundary on the thin side it falls below its own plateau to about 0.24 before recovering to 0.35, which is the fringe effect. The two traces have the same total density difference across the edge, so the same overall contrast, but the second is much steeper through the middle and carries a bright line and a dark line the first does not. The caption notes that the second trace is the one with the higher acutance and that the extra local contrast is manufactured by the chemistry rather than delivered by the lens.

Series	Position across the edge (µm)	Density
Continuous agitation, strong developer	-140.00	1.30
Continuous agitation, strong developer	-100.00	1.30
Continuous agitation, strong developer	-60.00	1.30
Continuous agitation, strong developer	-30.00	1.29
Continuous agitation, strong developer	-15.00	1.22
Continuous agitation, strong developer	0.00	0.83
Continuous agitation, strong developer	15.00	0.44
Continuous agitation, strong developer	30.00	0.37
Continuous agitation, strong developer	60.00	0.35
Continuous agitation, strong developer	100.00	0.35
Continuous agitation, strong developer	140.00	0.35
Restrained agitation, dilute developer	-140.00	1.30
Restrained agitation, dilute developer	-100.00	1.30
Restrained agitation, dilute developer	-70.00	1.32
Restrained agitation, dilute developer	-45.00	1.38
Restrained agitation, dilute developer	-25.00	1.45
Restrained agitation, dilute developer	-12.00	1.38
Restrained agitation, dilute developer	0.00	0.83
Restrained agitation, dilute developer	12.00	0.32
Restrained agitation, dilute developer	25.00	0.24
Restrained agitation, dilute developer	45.00	0.27
Restrained agitation, dilute developer	70.00	0.32
Restrained agitation, dilute developer	100.00	0.35
Restrained agitation, dilute developer	140.00	0.35

Both traces are drawn to show the argument and were not measured from a negative. The densities carry no authority: what the drawing asserts is the shape, that the edge with adjacency effects overshoots at both ends and is steeper in between while ending at the same two plateaux. The curve is drawn to show the shape, not measured from a real material. Your own materials will differ, and measuring them is what the sensitometry part of the course is for.

Two things about that pair are worth saying out loud, because they are what a reader wanting sharper negatives actually needs.

The overall contrast is identical. Both traces start at the same density and end at the same density. Nothing about the adjacency version records more information; the total range across the edge is what the exposure and the development time set. What changes is the distribution of that range, squeezed into a narrower band of position and overshot at each end.

The effect is local and therefore self-limiting. It exists because a gradient of inhibitor and a gradient of developer exist, and gradients need a boundary. In the middle of a large even area there is no boundary and no effect. That is why edge enhancement flatters detailed subjects and does nothing at all for a plain sky.

The three conditions, and the evidence for each

Adjacency effects are strongest when the developer near the film is allowed to become locally different from the developer in the tank. Three levers do that, and they are not equally well sourced.

Dilution: sourced directly, by two manufacturers

Kodak, on the D-76 sheet and on the chemicals sheet, in nearly the same words each time: “For greater sharpness, but with a slight increase in graininess, you can use a 1:1 dilution of this developer.”

ILFORD, on the HP5 Plus and FP4 Plus sheets, in the form of a recommendation table. Against Finest grain: PERCEPTOL, stock. Against Maximum sharpness: ILFOSOL 3 at 1+9 among the liquids and ID-11 at 1+3 among the powders. Same manufacturer, same film, the same developer at three dilutions, and the most dilute one is the sharpness recommendation.

The mechanism follows from the arithmetic. Dilute the stock and every dissolved species falls in the same ratio: less agent per unit volume, so the reservoir at any point in the emulsion is smaller and runs down sooner; less buffering and less sulfite, so the by-products are less thoroughly mopped up. Local exhaustion arrives earlier and goes further, and local exhaustion is the whole engine.

Reduced agitation: sourced, with the failure mode published alongside

Agitation is the transport variable that the kinetics lesson established, and Kodak states its purpose in one line: agitation “helps remove the by-products of development from the surface of the film so that fresh developer can act on the exposed silver halide”. Reduce it, and you are deliberately leaving the by-products where they were made.

Bostick and Sullivan publish Sandy King’s schemes for Pyrocat-HD, and they are the clearest manufacturer-published statement of the trade this course holds. Minimal agitation: 10 seconds every three minutes, times about 50 per cent longer than with normal agitation. Semi-stand: one part A, one part B and 200 to 400 parts of water, agitate for one minute at the start and 30 seconds at the half-way point, 40 to 50 minutes for slow and medium films and 50 to 60 for fast ones. The sheet’s own list of the formula’s advantages includes “no streaking or mottling with reduced agitation” — which tells you exactly what the failure mode of reduced agitation normally is.

Low sulfite: mechanism, not a sourced claim

The third condition is the one to be careful about. A low-sulfite developer should show stronger edge effects, and the argument is sound: sulfite is a silver solvent that softens the grain structure the effect is drawn on, and it is the acceptor that removes oxidised developer, so a bath carrying a great deal of it holds its by-products less locally.

This course has not found a source stating that claim directly, and does not assert it as established. What it has is circumstantial and worth having: ILFORD’s own tables never recommend the heavily solvent PERCEPTOL for maximum sharpness and always recommend a dilute ID-11 instead, and the developers marketed on definition — Pyrocat-HD, the FX family, the pyro formulae of the next lesson — are without exception low in sulfite. That is a pattern across manufacturers, not a mechanism anybody has published, and the difference between those two things is the difference between Rule 7’s “printers commonly find” and its “the sheet states”.

Compensating development: a shoulder made in the tank

Compensation is the same physics as adjacency, run at the scale of a whole highlight instead of the width of an edge.

A brightly exposed area consumes developing agent fast. In a dilute bath with little agitation, it consumes the agent in its own immediate neighbourhood faster than diffusion can replace it, and development there slows down or stops. A shadow area, developing slowly, never exhausts its neighbourhood at all and goes on at full rate for the whole time. The result is a negative whose highlights are held back while the shadows are not — a compressed top end and an untouched toe.

📷Why this is not the same as cutting the development time

Both reduce highlight density. They do it in different places, and the difference is the whole reason compensation is worth the trouble.

Cutting the time lowers the gradient of the entire curve. Highlights come down, and so do the mid-tones, and so does the separation in the shadows, which were never the problem. The negative prints flat everywhere.

Compensation acts where the density is high and leaves the toe alone. It manufactures a shoulder — the shape the top of a characteristic curve has when it stops climbing — out of local chemistry rather than out of the emulsion’s own design.

ADOX states the trade in a product datasheet, which is the most concrete evidence this course has for it: FX-39 II at 1+9 gives normal contrast with an increase in speed utilisation, while at 1+19 it is “for high-contrast subjects” and “acts to reduce contrast”, with the development time extended by 75 to 100 per cent and the speed utilisation falling back to the nominal film speed. In the sheet’s own framing, you can trade speed for compensating ability, within limits. That is a manufacturer describing a lever, with the price on it.

Stand development, and the physics with the sign reversed

Stand development is the limiting case: a dilute developer, a long time, and essentially no agitation. Wall’s 1924 formulary describes it as a method already old, and his assessment has aged well:

In the early days, it was put forward as a cure for every error in exposure, and the solutions used were so dilute that from 12 to 24 hours were required to obtain normal negatives. The only advantages of stand development are that the grain of the negatives is fine and the results uniform, if the developer be frequently agitated.

The qualification in that last clause is the whole of the modern semi-stand practice, arrived at a century early. Wall also records that stand development “is not economical, as most commercial tanks require a large amount of solution, which is, as a rule, so oxidised at the end of development as to be useless for a second time” — the aerial oxidation cost of leaving a large surface of dilute developer standing for an hour.

🧮Time does not scale with dilution, and somebody measured it

The rule of thumb says that a developer diluted five times needs five times the development time. Wall reports that Wratten and Wainwright tested it photometrically, and that it is false — and that the size of the error depends on something nobody would guess.

A plate needing 3 minutes in rodinal at 1:20 did not need 30 minutes at 1:200. It needed:

Water used to dilute	Time at 1:200
Air-free distilled water	42 minutes
Ordinary distilled water	46 minutes
Tap water	52 minutes

Three findings sit in that little table. The time ran 40 to 70 per cent longer than proportionality predicted, so the tenfold dilution behaved like a fifteen-fold one. The difference between the three rows is dissolved air: oxygen in the water consumes developing agent before the film gets any, and in a dilute bath there is little agent to spare. And Wall adds that pyro-soda and glycin “seem to be the only developers that are not affected by the water”, so the sensitivity belongs to the agent.

The practical consequence is that a dilution series run from arithmetic will come out under-developed, and that ILFORD’s advice to draw water off and let it stand before mixing a developer is not fussiness.

The failure modes, published by the people who sell the developers

Reduced agitation buys edge effects with unevenness, and the manufacturers document the unevenness in detail.

• Bromide drag. Developer loaded with released bromide and spent products is denser than fresh developer and sinks, retarding development in whatever it flows over. Part III gives the mechanism; it appears as streaks below dense areas, running with gravity rather than with the picture.
• Streaming and mottle, in opposite directions. Kodak’s troubleshooting table lists “streaks of non-uniform density” against excessive or uneven agitation and “mottle” against inadequate agitation. Both ends of the agitation range fail, differently.
• Currents that print. Kodak’s instruction is that agitation “should always consist of irregular or random movements that will not cause solution currents to flow over the film constantly in any one direction; these currents increase film density along their paths”.
• Edges dense, in a staining developer. Bergger’s PMK sheet lists “denser image edges” against “inadequate shaking, resulting in turbulence at the edges of the negative”, and prescribes agitation every 15 seconds — the opposite of minimal agitation, from a manufacturer whose developer is sold on definition.

That last one deserves a moment, because two Tier-1 sheets appear to disagree. Bergger requires frequent agitation for PMK and lists uneven colouring as the penalty for not giving it; Bostick and Sullivan publish a minimal-agitation and a semi-stand scheme for Pyrocat-HD and cite freedom from streaking under reduced agitation as an advantage of that formula over PMK. Read together they are consistent: the tolerance for reduced agitation is a property of the particular formulation, not of staining developers in general, and each maker is describing their own product honestly. A scheme published for one developer is not evidence about another.

The high-acutance formulae, and what this course prints

This is where the course’s provenance rule bites on this page, and the honest outcome is a short list.

Beutler’s developer. ADOX’s current datasheet for FX-39 II states that the product “is based on Willi Beutler’s Neofin Rot” and has been improved in every parameter — a manufacturer attributing a lineage. That is all the course has. It holds no publication of Beutler’s own formula, in any tier, and therefore prints none. What it can print is ADOX’s own published behaviour for the current product: one-shot use at 1+9 or 1+19, contrast controlled by dilution, capacity around 250 to 300 mL of working solution per film, and a film time table.

Crawley’s FX-1. The course holds one publication Geoffrey Crawley edited — The British Journal of Photography Annual 1972, at tier 2 — and its Acutance Formulae section prints his own FX series with their quantities. What the course has not done is read that section. The Annual is lending-restricted and marked copyright-cite-only in the bibliography, so it is not mirrored and cannot be, and repeated attempts to reach it through the Internet Archive’s search-inside route returned “Item not available”.

So this page prints no formula, no dilution and no attribution for FX-1, and it will not repeat one from a secondary listing — but the reason is that the quantities are in a document the course can cite and cannot read, not that no such document exists. That distinction matters here more than usual, because it is the difference between a formula nobody published and one this project has not got to.

Rodinal. The Adox datasheet was fetched and carries no extractable text, so this course quotes nothing from it: no dilution, no pH, no keeping claim and, in particular, no statement about stand development. What it has instead is a current manufacturer disclosing the agent class for the same developer type — Foma describes FOMADON R09 as “a liquid concentrate of a fine-grain, normal-working para-aminophenol negative developer” used at 1+25 or 1+50 — and ILFORD’s film sheets, which publish times for “Agfa Rodinal” at 1+25 and 1+50 without saying what is in it. A concentrate of a single high-activity agent, used at 1+50 or beyond, is the archetype of the low-solvent, easily-exhausted, high-acutance bath; the course teaches it as that, and prints no composition for the branded product.

⚗Why the class works, even where the formula is unknown

You can predict most of a high-acutance developer’s behaviour from three properties, all of which the manufacturers do disclose.

One agent, not two. Nothing regenerates the oxidised agent, so superadditivity is not available and the bath runs down where it works hardest. That is the compensation mechanism, built in.

Very little sulfite. Little solvent action, so the grain keeps its outline; little acceptor capacity, so the by-products persist near where they were made.

Very high dilution. A small reservoir per unit area of film, so local exhaustion arrives quickly, and a bath that is a one-shot by necessity rather than by preference.

Every one of those three is a statement about a class, and none of them requires the recipe. That is the pattern to reach for whenever a product’s composition is closed: ask what the disclosed behaviour implies about the class, and stop there.

Art track: when the edge helps, and when it is lying to you

The technical account above is neutral. The judgement is not, and the course states plainly which kind of sentence this section contains: these are conventions and experiential recommendations, held widely among printers, and not measurements.

Where edge effects flatter. Subjects made of boundaries. Foliage, brickwork, weathered timber, lettering, rigging, dry-stone walls, machinery. The border effect adds local contrast at every transition, and a print of such a subject reads as bitingly detailed at sizes where the actual resolution has long run out. Landscape and architecture are the traditional homes of the dilute single-agent developer for exactly this reason.

Where they harm. Faces. Skin is a subject with almost no true edges and a great many gentle gradients, and edge enhancement gives it an etched, slightly metallic quality that reads as unkind. The same is true of soft light generally, of mist, and of any subject whose point is a smooth transition.

Where they become visible as themselves. At large enlargement, a Mackie line stops being a subjective sharpening and becomes a halo — a visible bright rim along the dark side of a strong boundary, most obvious against a plain sky or a lit window frame. Once you can see it, you cannot unsee it, and it dates a print as surely as a technique does.

Wall’s 1924 formulary contains the most charming evidence that this was a settled craft judgement a century ago. Munkman’s stand table for rodinal at 1:100 gives three columns of development time at each temperature, headed Portrait, Architecture and Landscape. At 18 °C they are 18, 23½ and 32⅔ minutes. The subject sets the time, and the ratio between the longest and the shortest is nearly two to one.

▷The one comparison worth making before you choose a developer

Photograph a single subject that contains both kinds of content: a person standing in front of a brick wall or a hedge, in flat light, filling half the frame each. Two frames, identically exposed, on the same roll if you can cut it, or on two rolls of the same batch.

Develop one in D-76 stock with the manufacturer’s agitation, and the other in D-76 at 1+3 with agitation only at the start and once at the half-way point. Print both to the same mid-tone density at the largest size you can make, and look at the two halves separately.

You are not deciding which negative is better. You are finding out how much of the difference lands on the wall and how much lands on the face, because that ratio is what actually decides a developer for a body of work. Record the pair in your notebook against the formula versions; it is the sort of comparison people repeat every few years and never write down.

Recap

• Acutance is a measurement taken from a microdensitometer trace across a knife edge, built from the mean square gradient of the trace, with the reading limits set by Higgins and Jones’s smallest visible gradient of 0.005 D/µm. It is not resolving power, and no manufacturer in the corpus publishes it for a current film.
• The chemistry reaches further than the light. Fitted range constants of 15 to 20 µm for optical spread against 90 µm for chemical spread are why edge effects show at all — though those figures come from colour negative films in C-41 and only their ordering transfers.
• The border and fringe effects redistribute contrast, they do not add any. The two plateaux are unchanged; the transition between them is steeper and overshoots at both ends.
• Dilution and reduced agitation are the sourced levers. Kodak and ILFORD both publish the dilution claim; Bostick and Sullivan publish minimal-agitation and semi-stand schemes with times attached. Low sulfite is a mechanism this course argues and cannot cite.
• Compensation is local exhaustion at highlight scale: it makes a shoulder without flattening the toe, which is what distinguishes it from simply developing for less time.
• Every failure mode is published by the makers: bromide drag, mottle from too little agitation, streaks from too much or too uneven, denser edges from turbulence. Reduced agitation is a controlled trade, not a free gift.
• Beutler and Crawley are named here and not printed, because the course holds no publication of either formula; Rodinal is taught as a class from what Foma and ILFORD do disclose, because the Adox datasheet could not be read.

Check your understanding

Question 1. Why is acutance defined from the mean of the <em>squared</em> gradient across the edge rather than the mean gradient?

• Because density can be negative and squaring removes the sign
• Because two edges with very different shapes can share the same average gradient, and squaring rewards steepness wherever it occurs so the two are told apart
• Because it makes the units come out as density per micrometre
• Because the microdensitometer cannot measure a gradient directly

Show the answer and why

Answer: Because two edges with very different shapes can share the same average gradient, and squaring rewards steepness wherever it occurs so the two are told apart

The paper states the reason explicitly: the square is taken "in order to differentiate between knife-edge exposures that are very different in shape but may have the same average value for their respective gradients". A smooth ramp and a step with overshoots either side can cross the same total density over the same distance; only a measure that weights steep sections more heavily separates them, and it is precisely the steep, overshooting one that reads as sharp.

Question 2. A negative developed with strong adjacency effects and one developed with continuous agitation are traced across the same edge. What is the same in both traces and what differs?

• The maximum density differs; the shape is the same
• The two plateau densities are the same; the transition between them is steeper and overshoots at both ends in the adjacency version
• Everything differs, because the exposure was different
• The adjacency version records finer detail that the other one lost

Show the answer and why

Answer: The two plateau densities are the same; the transition between them is steeper and overshoots at both ends in the adjacency version

Adjacency effects redistribute contrast within the transition rather than adding range to it: the dense side and the thin side settle at the densities the exposure and the development time set. Nothing finer is recorded — a border effect cannot resolve detail the lens never delivered. What it does is add local contrast at every boundary, which the eye reads as sharpness at normal viewing distances.

Question 3. Wall reports Wratten and Wainwright finding that a plate needing 3 minutes in rodinal at 1:20 needed 42 minutes at 1:200 in air-free distilled water, 46 in ordinary distilled water and 52 in tap water. What does the spread between the three figures tell you?

• That the plates were of different batches
• That dissolved oxygen in the water consumes developing agent before the film does, and in a very dilute bath there is little agent to spare
• That tap water is contaminated with bromide
• That the temperature was not controlled

Show the answer and why

Answer: That dissolved oxygen in the water consumes developing agent before the film does, and in a very dilute bath there is little agent to spare

The only variable across the three rows is the air content of the water, and the effect is a 24 per cent lengthening of the time. In a bath at 1:200 the agent is present in such small quantity that the oxygen dissolved in ordinary water represents a significant fraction of it. This is aerial oxidation acting before development begins rather than during storage, and it is why ILFORD advises drawing water off and letting it stand before mixing.

Question 4. Bergger requires agitation every 15 seconds for PMK and lists uneven colouring as the penalty for less; Bostick and Sullivan publish a semi-stand scheme for Pyrocat-HD and cite freedom from streaking under reduced agitation as an advantage over PMK. How should these two Tier-1 sheets be read together?

• One of them must be wrong, and the more recent should be preferred
• They are consistent: tolerance for reduced agitation is a property of the specific formulation, so an agitation scheme published for one developer is not evidence about another
• Both are marketing and neither should be used
• Staining developers in general require frequent agitation

Show the answer and why

Answer: They are consistent: tolerance for reduced agitation is a property of the specific formulation, so an agitation scheme published for one developer is not evidence about another

Each maker is describing the product they sell, and one of them is explicitly comparing. The mistake to avoid is generalising an agitation scheme across formulations: whether a bath tolerates standing still depends on its dilution, its buffering, how fast it exhausts locally and how mobile its by-products are, all of which are formulation properties. Copy the scheme published for the developer you are actually using.

Question 5. Which of these are things this course could <em>not</em> establish from a source it has read, and therefore does not assert?

• That low sulfite increases adjacency effects
• That the names "Mackie line" and "Eberhard effect" attach to these phenomena on some documented authority
• That Kodak recommends D-76 at 1:1 for greater sharpness
• The composition of Beutler’s original developer

Show the answer and why

Answer: That low sulfite increases adjacency effects, That the names "Mackie line" and "Eberhard effect" attach to these phenomena on some documented authority, The composition of Beutler’s original developer

The Kodak dilution claim is printed twice in the corpus, in J-78 and the E-103CF chemicals sheet, so it is quoted. The other three are gaps: the low-sulfite claim is a mechanism argument supported only by a pattern across products, the two personal names have no attribution the course has read, and no publication of Beutler’s formula exists in the corpus at any tier, which is why ADOX’s statement of lineage is quoted and no recipe is printed.

Question 6. You want to hold back a bright sky without flattening the shadow separation in the foreground. Which approach addresses that, and why?

• Cut the development time by 25 per cent, because less development means less density
• Develop dilute with restrained agitation, because local exhaustion slows development where density is already high while shadow areas never exhaust their neighbourhood and continue at full rate
• Use a stronger alkali, because higher pH raises activity
• Add bromide, because a restrainer holds back the highlights

Show the answer and why

Answer: Develop dilute with restrained agitation, because local exhaustion slows development where density is already high while shadow areas never exhaust their neighbourhood and continue at full rate

Cutting the time lowers the gradient of the whole curve, so shadow separation goes with the sky. Compensation acts selectively because it is driven by consumption: the sky consumes its local reservoir of agent and stops, the foreground never does. Raising pH increases activity everywhere, and a restrainer raises the threshold and so acts hardest at the bottom of the scale — the opposite of what was wanted.

Check my answersClear