Reading the Negative as Evidence: Thin, Dense, Flat and Contrasty

Somebody hands you a strip of negatives and says it came out badly. Before you can say anything useful you have to answer a question they have not asked, and usually cannot ask, because the vocabulary collapses it: is this negative wrong in its overall level, or in its scale?

Those are two different faults with two different causes, and a great deal of bad advice comes from treating them as one. This page separates them, gives the two witnesses that settle which you have, lists the things that impersonate each, and ends with an honest account of what can and cannot be repaired afterwards.

Two independent quantities, and the confusion that follows from merging them

A developed negative has overall density — how much silver there is, everywhere — and it has contrast, the difference in density between the parts that got a lot of light and the parts that got little.

They are close to independent, and they have different masters:

• Overall density is mostly exposure. More light on the film means more developable grains everywhere, so the whole negative moves up.
• Contrast is mostly development. Longer, warmer, more concentrated or more vigorously agitated development steepens the relationship between exposure and density, so the same range of subject brightnesses is spread across a wider range of densities.

“Mostly” is doing real work in both sentences and this page will spend most of its length on the exceptions. But the first-order rule is right, and it is the rule the manufacturers’ own troubleshooting tables use. Kodak’s Z-133 has two rows, Light film — abnormally low density and Dark film — abnormally high density, and each gives the same pair of candidate causes: under- or over-development, or extreme under- or over-exposure. Two suspects, one appearance, and the table cannot tell them apart because a table cannot look at your negative. You can.

!Density is not contrast, and the course keeps them apart

This is one of the pairs the terminology rule refuses to blur. A negative can be dense and flat. A negative can be thin and contrasty. If you find yourself saying “underexposed” when you mean “low contrast”, stop and say which of the two quantities you are describing — the correction for one is not the correction for the other, and applying the wrong one makes the negative worse.

The four cases, and what each implicates

Two quantities, two directions each, four combinations. All four occur, and each names a different error.

The negative	Overall density	Contrast	What produced it	The tell
Thin and flat	Low	Low	Underexposure and under-development, or one severe enough to drag the other down	Shadows empty, highlights weak, whole strip looks grey against the light box
Thin and contrasty	Low	High	Underexposure with normal or extended development — the classic “pushed” negative	Rebate and shadows at base plus fog, but the highlights are dense and hard
Dense and flat	High	Low	Overexposure with under-development, or heavy fog on top of a normal negative	Everything grey-dark, including the rebate if fog is the cause
Dense and contrasty	High	High	Overexposure with normal or extended development, or over-development alone	Shadows carry plenty of detail, highlights are blocked and will not print

No combination is impossible, and it is worth saying why rather than leaving the reader to wonder, because the received wisdom sometimes claims one of them cannot happen.

The claim you sometimes meet is that a negative cannot be thin and contrasty, on the reasoning that short development lowers both density and contrast together. That reasoning is about development alone. But exposure and development are two knobs, and the case is produced by turning them in opposite directions: less light onto the film, and then the normal or a longer development time applied to it. The result is a strip whose shadows sit at the film’s floor — because nothing was recorded there — and whose highlights are dense, because the light that did arrive was developed fully. It is the standard consequence of shooting a 400-speed film at 1600 and developing for the higher index, which the manufacturers’ own tables provide for: ILFORD’s HP5 Plus sheet gives 7½ minutes in ID-11 stock at EI 400 and 14 minutes at EI 1600, and the second of those is exactly this negative made on purpose.

What is impossible is a combination in which the two quantities contradict the same measurement. A negative cannot have empty shadows and, at the same time, shadow detail. That is not a fourth case; it is a contradiction, and if you think you are looking at one, you are reading two different areas of the frame and calling them both shadow.

The four cases as four curves against one reference

• Reference: correct exposure and development
• Thin and flat
• Thin and contrasty
• Dense and flat (fog on the floor)
• Dense and contrasty

Drawn to show the shapes rather than measured from a material: the four faults are constructed from the reference by changing where the exposure lands and how steeply the density rises. Your own film's curve comes from the step-wedge series of Part XIII. 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.

The two witnesses

You do not have to guess which of the four you are holding, because the negative carries two independent witnesses and they answer different questions.

Shadow detail is the exposure witness

If the darkest subject tone you cared about carries no density above base plus fog, it was never recorded, and no development will bring it back.

That single observation settles roughly half of all cases, and it is worth understanding why it is so final rather than merely accepting it. Development does not create latent image; it amplifies it. A grain that received no photon carries no sensitivity centre for the developer to catch on, so extending the time gives it nothing to work with. What extended development does do is continue to build density where there already is some — which is the highlights — so the negative gets more contrasty while the shadows stay exactly as empty as they were.

So the first thing to look at on a suspect negative is not the middle of the frame. It is the darkest part of the subject that was supposed to show texture, held against the rebate. If you cannot see a difference, the exposure was short. If you can, the exposure reached the film and the fault is somewhere else.

Highlight density is the development witness

Having established that the shadows are where they should be, look at the highlights.

• Highlights thin while the shadows are correct means the development did not go far enough: time short, temperature low, dilution too great, agitation too little, or a bath with nothing left in it.
• Highlights blocked while the shadows are correct means development went too far — or that the subject’s own brightness range was longer than the film and the development combination could hold, which is a tone reproduction problem rather than a fault and is Part XIII’s subject.

The two witnesses are independent, which is what makes them worth having. Read in that order — shadows first, then highlights — they reduce four cases to one in about fifteen seconds.

The rebate is the control that came free with the film

The third piece of evidence is the one nobody paid for.

The rebate is the strip of film outside the frame mask. No light formed by the lens ever reached it. Whatever density it carries after processing is base plus fog: the support, its dyes, and whatever silver development produced in the absence of any exposure. It is your process floor, measured on the same film, in the same tank, on the same day.

That makes it a control in the strict sense. If the rebate is where it always is, the film’s storage and your development conditions were normal, and any density fault is in front of the shutter. If the rebate is raised, something acted on the whole film at once, and the diagnosis moves to the fog page before anything else is considered.

=The two rebate readings a beginner can actually make

Against clear film. Cut a scrap of unexposed film from the leader of an undeveloped roll of the same stock, fix it without developing, and keep it. That is base without fog. Lay your processed rebate over it on a light box: the difference you can see is the fog.

Against a known-good strip. Faster and usually enough. If your rebate is visibly darker than the rebate of a film you were happy with, you have a raised floor, and you have found it without an instrument.

Neither is a measurement. Both are a ranking, and a ranking is what a diagnosis needs.

The sensitometric account of all of it

Everything above can be restated in the vocabulary of the characteristic curve, and the restatement is worth doing because it makes the exceptions obvious.

Exposure slides the subject along the log-exposure axis. The curve belongs to the film and the development; the subject’s range of brightnesses is a fixed length laid on that axis, and the exposure decides where that length is laid. Slide it left and the shadow end falls off the toe onto the flat part where density does not change with exposure — which is what “empty shadows” means in this vocabulary. Slide it right and the highlight end climbs onto the shoulder, where density again stops changing with exposure — which is what “blocked highlights” means.

Development changes the gradient. More development raises the slope of the straight-line section, so a given range of exposures is rendered as a wider range of densities. That is the contrast index of Part XIII, and it is the number you change when a negative prints too flat or too hard on your normal paper grade.

Fog raises the floor and eats the shadows from below. This is the one that surprises people. Fog does not simply add a constant to every density, leaving the picture intact underneath. It adds density where the least was, and near the toe the curve is nearly flat, so a rise of a tenth in the floor can swallow a whole zone of shadow separation while leaving the highlights looking almost untouched.

Fog raises the floor, and the shadow separation is what it takes

• Normal base plus fog
• Raised base plus fog

Drawn rather than measured. The point is the geometry: the toe is where the two curves are furthest apart in what they can separate, and the toe is where the shadows are. 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.

The impostors

Both diagnoses have a set of causes that produce exactly the right appearance for entirely the wrong reason, and every one of them will send you to change something that was never at fault.

Things that look like an exposure error and are not

A film past its date, or stored warm. Age costs speed and gains fog, and a film that has lost a stop produces a thin negative from a perfectly correct meter reading. Kodak’s Tri-X sheet asks for unexposed film to be stored at 24 °C or lower in the original sealed package, and for film to be processed as soon as possible after exposure. Neither instruction is decorative. The diagnostic tell is the rebate: age fog raises the floor as well as costing speed, so an aged film is usually thin with a raised rebate, which is a combination underexposure cannot produce.

A meter reading the wrong thing. A meter is an instrument for measuring a patch of the world, and the patch is decided by where you point it. A bright sky in the corner of a reflected reading, a subject much darker than mid-grey, or an incident reading taken in a different light from the subject all produce a systematically wrong exposure with a perfectly functioning instrument. The tell is consistency: this fault is usually consistent within a scene type and disappears when the scene type changes.

A shutter running fast. Mechanical shutters drift, and they drift most at the speeds you use most. A shutter one stop fast underexposes every frame at that speed by one stop while the frames at other speeds are correct. The tell is that the error tracks the shutter speed and nothing else, which a frame-by-frame comparison against the exposure record will show at once.

Reciprocity failure on a long exposure. For exposures beyond about half a second, the film’s response is no longer proportional to the total light, and the metered time under-delivers. ILFORD publish the relation for HP5 Plus as an adjusted time that is the metered time raised to the power 1.31, with no correction needed between half a second and one ten-thousandth. That exponent is worth working once, because it is not a small correction: a metered 4 seconds becomes about 6.4 seconds, a metered 30 seconds becomes about 92, and a metered 2 minutes — 120 seconds — becomes about 570 seconds, which is nine and a half minutes. A pinhole exposure metered without this correction is underexposed by a factor that grows with the exposure, and the negative that results is thin in exactly the way an incompetent meter reading would be.

A filter factor forgotten. A deep red filter can cost three stops. ILFORD warn on the HP5 sheet that with some automatic exposure cameras the correction given for deep red and orange filters can leave negatives underexposed by as much as one and a half stops even with through-the-lens metering. The tell is that the fault appears on exactly the frames where the filter was on.

A lens that flares. Flare works the other way and is worth knowing for that reason: it adds non-image light, raising the shadow densities and lowering contrast. A flared frame looks like a fogged one, and it is distinguished by being confined to the image area — flare comes through the lens and cannot touch the rebate.

Things that look like a development error and are not

A developer two degrees from where you think it is. ILFORD’s own temperature compensation chart turns an 8-minute development at 20 °C into 7:15 at 21 °C and 8:45 at 19 °C — from which the course takes the working figure of about 9 per cent of the development time per degree Celsius near 20 °C. Two degrees is therefore worth close to a fifth of the time. Kodak’s Z-133 is blunter about the professional case: temperature variations greater than ±0.3 °C in the developer affect process control and image quality.

A thermometer that is precise and wrong. A digital probe reading to a tenth of a degree that is calibrated a degree and a half high will give you beautifully repeatable, consistently under-developed negatives, and the repeatability is what makes it invisible. ILFORD’s own process control introduction recommends keeping a good liquid-in-glass thermometer to check a built-in sensor against, on the grounds that very little can go wrong with one. That is the cheapest instrument audit in the darkroom.

A timer started late. The time that matters is from the developer entering the tank to the developer leaving it, and pouring 300 mL into a spiral tank takes a real number of seconds. ILFORD’s first-film guide handles this by having you start pouring out fifteen seconds before the mark, so that the pour is inside the time rather than after it. Whichever convention you use, use one, and write it down — because a change of convention alone can shift the effective time by half a minute.

An agitation scheme changed without noticing. Agitation controls how fast fresh developer reaches the emulsion, so it changes the effective development rate as surely as the clock does. ILFORD ask for four inversions in the first ten seconds and four again in the first ten seconds of each further minute; Kodak’s AJ-3 asks for five to seven inversion cycles in five seconds, repeated every thirty seconds. Those are different schemes and they will not give the same contrast at the same time. Neither is wrong. Using one on Monday and the other on Thursday, with the same clock, is.

A bath at the end of its capacity. Kodak’s D-76 sheet gives a useful capacity of 16 rolls per gallon — four per litre — at full strength, with a footnote that is easy to skip: increase the development time by 15 per cent after every four rolls per gallon processed. A worker who reuses a litre of stock for a fifth and sixth film without that compensation is under-developing on purpose and calling it a mystery.

What settles it: instruments, and what to do without one

A densitometer reads density as a number, and a number is what turns “looks thin” into “the rebate reads 0.24 where it read 0.11 last month”. Part XV builds one, and Part XIII uses it to produce your film’s actual curve. With one, the diagnosis is arithmetic: read the rebate, read a shadow that should have detail, read a highlight, and compare all three with the same three readings from a session you were happy with.

Without one, a light box and a strip of known-good film settle almost as much, because the eye ranks well even though it measures badly. Lay the two strips edge to edge, rebate against rebate, and look at the join. A difference you can see at a joined edge is real. A difference you think you can see between two strips held apart, in different parts of your visual field, frequently is not.

🧮What one instrument's specification buys you

The commercial transmission densitometer the course uses as a reference publishes a repeatability of ±0.01 density and a linearity of ±0.02 over its range. Set that beside the quantity you are trying to detect. A rebate that has risen from 0.11 to 0.24 is a change of 0.13 — thirteen times the instrument’s repeatability, and unmissable.

A dry-down difference of 0.03 on a print, by contrast, is inside the linearity figure and only just outside repeatability, which is why the printing part insists on repeated readings for that measurement and not for this one. The instrument does not have one precision; it has a precision relative to the size of the thing you are asking about, and knowing which side of that line your question falls on is most of measurement.

Working a negative in order

From the strip in your hand to a named cause

1. 1Read the rebate firstAgainst clear fixed base, or against a known-good strip. Raised? Go to the fog page before anything else — a raised floor changes the meaning of every other reading.
2. 2Are the edge numbers legible and normal?Faint or missing edge printing means the developer did not do its job, whatever the camera did. This convicts development in one look.
3. 3Find the darkest subject tone that should show textureAny density above the rebate? No: underexposure, and no development change will fix the negatives you already have. Yes: exposure reached the film; go on.
4. 4Read the highlightsThin with correct shadows means under-development. Blocked with correct shadows means over-development, or a subject range longer than the process could hold.
5. 5Is it every frame or one?Every frame with the same error points at the process or a systematic exposure error. One frame points at that exposure.
6. 6Check the record against the impostorsTemperature measured or assumed; timer convention; agitation scheme; bath age and running total; filter, shutter speed and exposure length for the frames concerned.
7. 7Name the cause, and name what would have looked different if you were wrongIf nothing would have looked different, you have a story rather than a diagnosis.

Prevention as a system rather than a resolution

The prevention for every fault on this page is the same and it is not “be more careful”.

A metering method you use every time, so that when it fails it fails consistently and is therefore diagnosable. An inconsistent method produces inconsistent errors, and inconsistent errors cannot be corrected.

A personal exposure index, established rather than assumed. The published ISO speed is a property of the film measured under a defined development; your effective speed depends on your developer, your agitation, your thermometer and your meter’s habits together. Part XXVII’s development-time series is where the course derives it as a measurement rather than a guess.

A processing table you actually follow: film, developer, dilution, time, temperature, agitation scheme, and the running total on the bath. Six fields. It is the difference between a fault you can diagnose in ten minutes and one you cannot diagnose at all.

A control strip whenever anything changes — a new bath, a new batch of film, a new thermometer, a new room temperature. One strip is cheaper than one lost roll, and enormously cheaper than three.

Atlas entries this page owns

Seven entries in the troubleshooting atlas belong to this page and are written from it: thin negative, dense negative, flat negative, excessive contrast, blocked highlights, empty shadows and frame-to-frame density variation.

The last of those is the one worth reading even if the others look obvious, because inconsistency between frames on one film is a different class of fault from a whole film being wrong: a whole film is the process, and frame-to-frame is the camera, the metering or the light.

Closing: what reduction and intensification can and cannot repair

Everything above is diagnosis. This last section is the only place in this part where the course discusses treating a negative chemically after the fact, and it exists mostly to set out the limits, because the folk literature on reducers and intensifiers promises far more than the chemistry delivers.

Reduction removes silver, and there are three ways to do it

A reducer oxidises image silver and dissolves it away. Density goes down. Nothing else about the negative improves; you are subtracting, and the only question is where the subtraction falls.

Kodak’s 1928 primer sets out three classes, and the distinction between them is the whole of the technique:

Cutting, or subtractive. The primer’s own definition: a cutting reducer “removes an equal quantity of silver from all parts of the image, and consequently removes a larger proportion of the image from the shadows than from the highlights”. Equal amount everywhere means a larger fraction where there was least, so contrast rises as density falls. Farmer’s reducer — potassium ferricyanide with hypo — is named as the typical member of the class, and Kodak Limited’s own header for the formula reads “a cutting reducer for correcting over-exposure and clearing shadow areas of negatives and high lights of prints”.

Proportional. The primer defines these as acting “on all parts of the negative in proportion to the quantity of silver present there; hence they exactly undo the action of development”. Contrast falls, because every density is scaled by the same factor and the differences between them shrink with it. The primer is honest about the practical position: no single substance forms an exactly proportional reducer, and the nearest thing is a mixture of permanganate (slightly cutting) with persulphate (flattening).

Flattening, or superproportional. These act “very much more on the heavy deposits than on the light deposits”, so the highlights come down and the shadows are barely touched: contrast falls hardest of the three. The primer names ammonium persulphate as the only one known and does not flatter it — its action is “somewhat uncertain”, it occasionally refuses to act, and it always acts more rapidly as the reduction progresses, which is a difficult thing to control by eye.

The three modes, drawn as the curve each one leaves behind

• Before reduction
• Subtractive (cutting): equal amount everywhere
• Proportional: an equal fraction everywhere
• Superproportional (flattening): most from the densest

Drawn to show the three behaviours, not measured from a reduced negative: each curve is the reference transformed by the rule its class is defined by. Kodak's own classification is the source of the three rules; the shapes are the course's illustration of them. 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.

What that means for the two thin negatives

On a thin-but-contrasty negative, a cutting reducer makes things worse and the geometry says so. There is almost nothing in the shadows to begin with. A reducer that removes an equal quantity everywhere removes most of what little is there, so the small separations that were the last trace of shadow detail are erased, and the contrast — which was already too high — rises further. That negative does not want reduction. It wants a softer paper grade, and it wants a longer exposure next time.

On a dense-but-flat negative, reduction can genuinely help. There is silver to spare, the overall level is too high for a comfortable printing time, and taking density off with a cutting reducer raises the contrast that was lacking. This is the case Kodak’s own header describes, and the primer adds one more use worth knowing: Farmer’s is “especially useful for clearing negatives or lantern slides which show slight fog”, because fog is a thin even deposit everywhere and a cutting reducer removes exactly that first.

Why no intensifier restores an empty shadow

An intensifier adds material to the silver that is already in the negative — the 1928 primer: intensification “is photographically the opposite of reduction… done by the deposition of some material on the silver image”.

Read that definition once more and the limit is immediate. An intensifier acts on silver that is there. Where the negative carries nothing above base plus fog, there is no silver to deposit anything on, and the intensifier deposits nothing. The highlights, which have plenty of silver, gain plenty of density. The result is a more contrasty negative with exactly the same empty shadows — which is usually a worse negative than the one you started with, because now it will not print on any grade.

✕The commonest wrong hope in the whole of failure analysis

“The negative is thin, so I will intensify it.”

Thin from under-development — silver everywhere, just less of it, with the shadows still separated — can be helped, because there is a deposit at every density for the intensifier to work on.

Thin from underexposure — nothing above base plus fog where the shadows should be — cannot. The information was never recorded. Intensification cannot record it retrospectively, and neither can anything else.

The two look similar on a light box and are told apart by exactly one observation, which is the first witness on this page: is there any density above the rebate in the darkest tone you cared about?

The course’s position, stated plainly

The reducers this course teaches are the ferricyanide-thiosulfate family, and they are in the formulary at Level B: R-4a as Kodak Limited printed it in 1949, R-4 as the weaker 1928 formula, and R-4b, the two-bath form Kodak describes as almost proportional rather than cutting. Their quantities, mixing, mechanism and hazards live on those pages and are not repeated here.

Level B, and the reason is one incompatibility. The international chemical safety card for potassium ferricyanide states that it reacts with acids, generating a toxic hazard, and that the solid decomposes on heating to produce toxic gases including hydrogen cyanide. Princeton’s guidance for photography is more specific: it will release hydrogen cyanide if heated, if hot acid is added, or on exposure to strong ultraviolet such as a carbon arc, and it records that cases of cyanide poisoning have occurred through treating Farmer’s reducer with acid. That sentence names this formula. In practice it means no stop bath on the same bench run, no acid fixer into the reducer’s waste, no acid used to clean a tray that has held ferricyanide, and no warming of the ferricyanide stock. The formulary pages carry the controls in full and you read them before you mix anything.

Of the intensifiers, the course carries a procedure for one only: IN-5, the silver intensifier, at Level B. The chromium and mercury intensifiers of the historical literature are Level D, treated in Part XXVI as chemistry and history, with no working procedure anywhere in this course — not on their formulary entries, not on that page, and not here.

And the position that matters more than any of them: reduction and intensification are irreversible, and a paper grade is not. Before you put a negative in a bath, print it. A grade harder, a grade softer, some burning-in and a different exposure will rescue more negatives than chemistry will, and none of it can be got wrong in a way you cannot undo.

Recap

Overall density is mostly exposure; contrast is mostly development; treating them as one quantity is the root of most bad negative diagnosis. Four combinations occur and each names an error. Shadow detail is the exposure witness and settles about half of all cases on its own, because development amplifies latent image and cannot invent it; highlight density is the development witness; and the rebate is a free control that says what your process floor was. A long list of impostors — aged film, a mis-aimed meter, a fast shutter, uncorrected reciprocity, a forgotten filter factor, two degrees of temperature, a mis-calibrated thermometer, a changed agitation scheme, a bath at the end of its capacity — mimic one or other diagnosis exactly. Afterwards, a cutting reducer lowers density and raises contrast, so it helps a dense flat negative and ruins a thin contrasty one; and no intensifier returns a shadow that was never exposed, because there is nothing there for it to act on.

Check your understanding

Question 1. Four negatives are described by measurement. Which is under-developed rather than underexposed? (a) rebate 0.11, darkest textured shadow 0.09, brightest highlight 0.55. (b) rebate 0.12, shadow 0.28, highlight 0.62. (c) rebate 0.38, shadow 0.51, highlight 1.90. (d) rebate 0.13, shadow 0.30, highlight 2.60.

• (a), because everything is low
• (b), because the shadow carries real density above the rebate — so exposure reached the film — while the highlight has climbed only 0.34 above that shadow, which is too small a range to print normally
• (c), because the rebate is high
• (d), because the highlight is very dense

Show the answer and why

Answer: (b), because the shadow carries real density above the rebate — so exposure reached the film — while the highlight has climbed only 0.34 above that shadow, which is too small a range to print normally

Read the two witnesses in order. In (a) the shadow reads below the rebate, meaning nothing was recorded there: that is underexposure, and no development will retrieve it. In (b) the shadow is 0.16 above the rebate, so light did reach the film, and the whole range from shadow to highlight is only 0.34 — the development stopped short. (c) has a raised floor and belongs on the fog page before anything else is decided. (d) has correct shadows and a very dense highlight, which is over-development or a long subject range, not under-development.

Question 2. A film is developed for half its correct time. State what happens to shadow detail, to highlight density, and to the paper grade you will need.

• Shadows lost, highlights unchanged, softer paper needed
• Shadow densities fall only a little because the toe was nearly complete early, highlight densities fall a great deal because they were still building, so the whole range compresses and a harder grade of paper is needed to restore the print contrast
• Everything halves, and the same grade prints it
• Shadows and highlights both double, and a softer grade is needed

Show the answer and why

Answer: Shadow densities fall only a little because the toe was nearly complete early, highlight densities fall a great deal because they were still building, so the whole range compresses and a harder grade of paper is needed to restore the print contrast

Development builds density fastest where the most latent image is, so cutting the time takes proportionally more from the highlights than from the shadows. The gradient of the curve falls: the same subject range now produces a smaller density range. The negative is thin and flat, and the printing answer is a harder grade — which recovers the contrast but not the highlight separation that was never developed, and which also prints the grain and any fog harder.

Question 3. A negative is thin overall but has a long, contrasty scale wherever it carries any density at all. Would reduction or intensification help, and which mode?

• Subtractive reduction, to clear the fog and open the shadows
• Superproportional reduction, to bring the highlights down
• Silver intensification, to raise the whole negative
• Neither, honestly: the shadows are empty so there is nothing to intensify, and any reducer takes away the little density that remains at the thin end while raising a contrast that is already too high — the answer is a softer paper grade and more exposure next time

Show the answer and why

Answer: Neither, honestly: the shadows are empty so there is nothing to intensify, and any reducer takes away the little density that remains at the thin end while raising a contrast that is already too high — the answer is a softer paper grade and more exposure next time

This is the case that catches people because it looks like two problems and is really one. The negative is thin because the exposure was short, so the shadow end carries nothing an intensifier could deposit on. It is contrasty because development was normal or extended on top of that short exposure. A cutting reducer removes an equal quantity everywhere and therefore removes most of what little the thin end has, raising contrast further. Superproportional reduction would lower the contrast, but it acts on the dense areas and still cannot put shadow detail back; and the course teaches no persulphate reducer. The printing answer is real and the chemical answer is not.

Question 4. Why is a raised rebate density a stronger piece of evidence than a raised density in the image area?

• Because the rebate is thicker film
• Because no light formed by the lens can reach the rebate, so a raised rebate excludes exposure, shutter and aperture in one observation and points at the whole-film causes: development conditions, the film's own history, or light that reached it outside the camera
• Because the rebate is measured more accurately
• Because the rebate always develops faster than the image area

Show the answer and why

Answer: Because no light formed by the lens can reach the rebate, so a raised rebate excludes exposure, shutter and aperture in one observation and points at the whole-film causes: development conditions, the film's own history, or light that reached it outside the camera

The rebate sits behind the frame mask and is a genuine control: same film, same tank, same day, and no image exposure. Its density is base plus fog by construction. That is why it is the first reading in the diagnostic order — it either eliminates a whole family of causes or redirects the entire diagnosis to the fog page before any other observation is interpreted.

Question 5. A worker develops a fifth and sixth roll in the same litre of D-76 stock at the published time and gets progressively flatter negatives. What does Kodak's own data sheet say about this?

• That D-76 has unlimited capacity at full strength
• That the useful capacity is 16 rolls per gallon — four per litre — and that development time must be increased by 15 per cent after every four rolls per gallon processed, so the fifth and sixth rolls needed longer than the published time
• That the developer should be diluted further for later rolls
• That the temperature should be raised for later rolls

Show the answer and why

Answer: That the useful capacity is 16 rolls per gallon — four per litre — and that development time must be increased by 15 per cent after every four rolls per gallon processed, so the fifth and sixth rolls needed longer than the published time

This is one of the impostors: the negatives look under-developed and they are, but the clock was right. Capacity and exhaustion are different from time and temperature and have their own compensation. Note also the sheet's separate instruction that D-76 diluted 1+1 is mixed just before use and discarded after one batch — a dilution is not a smaller quantity of the same thing, it is a one-shot bath.

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