Dry-down error

Owned by print faults and poor maximum black. The measurement belongs to Part XVIII, which designs the experiment; this entry is the fault it prevents.

What you see

A print that looked right in the fixer or the wash, and is too dark, with the light tones closed up, when it is dry.

The loss is not uniform. What goes first is the separation in the upper mid-tones and the highlights — the delicate light modelling that made you like the wet print — while the blacks look much as they did.

It is consistent. Every print from every session drifts the same way, which is what makes it an error to be corrected rather than a defect to be diagnosed.

Likely causes

1. Judging the print wet and printing to that judgement.
2. Inspecting under a bright darkroom lamp at close range, when the print will hang on a wall in room light.
3. Applying a remembered fraction of a stop as a uniform correction to an effect that is not uniform across the tonal scale.
4. Comparing a wet print against a dry reference print, which compares two different objects and guarantees a mismatch.

What is happening: the chemistry and physics

Two things change between the wet print and the dry one, and separating them is the whole subject.

The material changes. The gelatin loses water; its thickness, its surface and the way it returns light all change with it. This is the component a densitometer reads, and it is real.

The viewing conditions change. A wet print is judged under a bright inspection light at arm’s length; a dry print is judged on a wall in room light. A brighter light makes the deepest tones look deeper and the separations look wider. Both changes run in the same direction, so the wet print flatters twice.

!Two things the course will not give you, and why the refusal is the useful part

A number. Part XVIII establishes that no manufacturer in this course’s corpus publishes a dry-down figure for a developing-out silver gelatin paper. The published maximum densities — ILFORD’s 2.15 and 2.05, Foma’s 2.0 glossy and 1.6 matt — are figures for the dry paper and say nothing about the wet-to-dry difference. So a figure quoted here would be invented, and it would be invented for a paper that is not yours in a process that is not yours.

A mechanism for the material component. Part XVIII states plainly that no source in the corpus gives one. The viewing-condition component is straightforward and is explained above; the material component is measurable and unexplained, and the page says so.

What replaces both is a measurement you make once. And it turns out to be more useful than a number would have been, because the difference is not the same at every density: Part XVIII’s own analysis finds it smallest at paper white, largest through the upper mid-tones, and narrowing again towards black. A single figure applied uniformly is therefore wrong everywhere except at one density — and it is wrong in the direction that costs the highlights, which are exactly the tones people are trying to protect.

Diagnostic questions

• Does it happen on every print? A consistent, one-directional drift is dry-down. An inconsistent one is something else — a developer drifting through a session, or a lamp warming.
• How bright is your inspection light, and how does it compare with where the print will hang? Half the effect is here, and no chemistry addresses it.
• Are you comparing a wet print with a dry reference? That comparison cannot be made and is the commonest procedural cause.
• Which tones lost most? Upper mid-tones and highlights is the expected shape. A uniform darkening suggests you are looking at an exposure error instead.
• What surface is the paper? Foma publish 2.0 for their glossy surface and 1.6 for the matt version of the same paper, and a surface that returns less light dry may behave differently wet.
• Has the drying method changed? Air-dried, heat-dried and glazed prints are three different objects, and ILFORD list all three as options on the same sheet.
• Have you ever measured it on this paper? If not, every compensation so far has been a guess.

Corrective action

Reprint with a measured correction, not with a remembered one.

The method is Part XVIII’s: read the same patches wet and dry, convert the density difference into an exposure correction using the local gradient of the paper’s curve, and state what the conversion assumes. Five patches, not one, because the difference varies with density.

And judge dry. The simplest correction of all is not to make the judgement in the wrong condition: dry a work print — ILFORD give RC papers 10 to 20 minutes at room temperature — and decide from it.

Prevention

Judge prints dry, under the light they will be seen in. This removes the viewing-condition half of the effect entirely, and it costs twenty minutes on an RC work print.

Measure your own dry-down once per paper and process, and record it as a curve rather than a number. It is one afternoon and it is good for as long as you use that paper.

Keep the drying method constant. Air-dried, heat-dried and glazed are different, and a correction established for one does not transfer.

Keep a dry reference print of a negative you know, made on the paper you use, and compare new work against it dry. A wet print compared with a dry reference is a comparison of two different objects.

And standardise the inspection light. A standard exists for viewing conditions for reflection prints; you do not need to meet it to benefit from the principle, which is that the light you judge under should not change from session to session.