Dense negative

Owned by reading the negative as evidence, which sets out the four combinations of density and contrast and the two witnesses that separate them.

What you see

A negative that is dark everywhere. ILFORD’s own description of a correct negative is the reference to measure it against: “some parts almost clear (like the rebates) and other parts so dense you can only just read print through them”. On a dense negative the highlights are past that — print is not readable through them — and the shadows, which should be near the rebate, carry obvious density.

Printing times are long, the grain is emphasised, and the highlights block up on any grade.

Likely causes

1. Overexposure. More light everywhere, so the whole negative moves up including the shadows.
2. Over-development — too long, too warm, too concentrated, or too much agitation.
3. Fog, from any of the fog page’s sources, which raises the floor and everything above it.

Kodak’s Z-133 lists exactly two causes against Dark film — abnormally high density: “overdevelopment or extreme overexposure”, and “light fog”. The order of its corrective action is worth copying: check developer time, temperature and mixing first, then check the camera exposure.

What is happening: the chemistry and physics

Exposure decides how many grains carry a developable sensitivity centre; development decides how many of those are reduced and how far. Give more of either and there is more silver.

The two differ in where the extra silver lands. Overexposure slides the whole subject range to the right along the log-exposure axis, so the shadows come up off the toe and gain the most in relative terms while the highlights may run onto the shoulder and gain least. Over-development steepens the gradient, so the highlights gain most and the shadows least. Fog adds everywhere and to the floor first.

!The rebate settles it, and it costs nothing

Read the rebate against a known-good strip or a piece of clear fixed base.

• Rebate normal, shadows and highlights both up — overexposure. The process floor is where it belongs, so the extra density came through the lens.
• Rebate normal, highlights far up and shadows only a little — over-development. The gradient has risen, which is what over-development does.
• Rebate raised as well — this is not a density fault at all. It is fog, and the diagnosis moves there before anything else is interpreted.

No light formed by the lens can reach the rebate, so a raised rebate excludes exposure in one observation.

Diagnostic questions

1. What does the rebate read against a reference? The branch above.
2. Are the edge numbers unusually dark and heavy? Edge printing is a factory latent image and only development brings it up. Heavy edge numbers point at development, not at the camera.
3. How far above the rebate is the darkest important shadow? Well above, on every frame, is overexposure; barely above while the highlights are impenetrable is over-development.
4. Every frame, or some? Every frame with the same excess points at the process or a systematic exposure error. Some frames points at those exposures.
5. What were the time and temperature, measured rather than intended? Two degrees is worth close to a fifth of the development time near 20 °C.
6. What was the running total on the bath? A fresh bath used at a time established on a tired one over-develops.

Corrective action

Print it. A dense negative is far more printable than a thin one, because the information is there; it costs exposure time and it costs some highlight separation where the shoulder has flattened.

Where the density is genuinely unmanageable, the ferricyanide-thiosulfate reducer takes density off and raises contrast, which suits a dense negative that also prints flat and does not suit one that is already contrasty. It is at Level B on its formulary page, the hazard is the ferricyanide’s incompatibility with acid, and reduction is irreversible. Print first.

Prevention

Establish which of the two it was and change only that. Overexposure is a metering or a film-speed matter; over-development is time, temperature, dilution and agitation, written into a processing table as four numbers rather than as habits.

Keep the rebate reading. One number per session, recorded, turns the branch at the top of this entry into arithmetic instead of an impression.

Run a control strip when anything changes — a new bath, a new thermometer, a new agitation scheme.