Meg Turner

Printmaker and photographer working out of New Orleans, Louisiana. Her practice spans prints, photography, and installation projects that respond to the landscape and the community she is part of.

In addition to her own work and contract printing, Meg serves as the master printer for local photogravure and wet collodion artist Josephine Sacabo. She founded the New Orleans Community Printshop and has since stepped back from a leadership position to focus on her studio practice.

She shoots primarily with a 4×5 Crown Graphic press camera, working in film and wet collodion.

A circular portrait embedded in a dramatic magenta-to-indigo gradient field, with deep black edges framing the composition

The Physics of Light in the Darkroom and How It Shapes the Image

Light behaves in the darkroom the same way it behaves everywhere else, which is to say it obeys physics rather than intuition. Photographers who work in wet-process printmaking are essentially conducting a small optics experiment every time they pull a print from the fixer. Whether working out of a converted shed in Hobart or a community-access space in Melbourne, the same wavelengths, the same silver halide chemistry, and the same laws of illumination apply. Understanding those laws changes the print from a happy outcome to a deliberate one.

This article traces the journey of a photon from a darkroom enlarger through silver gelatin paper and into the eye of a viewer in a gallery. It looks at safelights, enlarger optics, exposure, and the latent image, and offers a few working habits that translate theory into cleaner negatives and richer prints.

Wavelengths the Emulsion Sees

Photographic paper is built from silver halide grains suspended in gelatin, and those grains are not equally sensitive to every colour of light. Silver bromide crystals respond most strongly to the blue and ultraviolet end of the visible spectrum, which is why traditional black-and-white paper can be handled under a deep red safelight without fogging. Films labelled orthochromatic extend that response into green, while panchromatic emulsions cover the full range from roughly 400 to 700 nanometres, including the red portion that older emulsions could not see.

This spectral bias has practical consequences. A face lit by tungsten light, which skews warm, will render very differently on orthochromatic film than it does on a modern panchromatic stock. Printmakers who scan or digitally invert negatives need to remember that the print on the easel is fundamentally a record of how the silver salts translated those wavelengths into density. The eye of the photographer matters too: red safelights can deceive you into thinking a print is darker than the silver actually records it.

In Australian print rooms, where many practitioners use Ilford Multigrade and select paper grades from 00 to 5, understanding the filter-paper relationship is a daily exercise. A grade 2 filter transmits a relatively broad band of blue and UV light, while a grade 5 filter narrows that band and produces a harder, more contrasty print. Photographers working between Sydney and Ballarat notice how altitude and humidity shift exposure times slightly, but the physics of contrast control stays constant.

The Safelight Spectrum and Safe Illumination

The word "safelight" is a misnomer borrowed from convention. No light in a working darkroom is truly safe in absolute terms; some light is just safer than others, because its wavelengths fall outside the peak sensitivity of the emulsion in use. A typical black-and-white darkroom uses a red or amber filter with a 15-watt bulb mounted at least a metre from the paper surface, angled so the paper receives reflected rather than direct light.

Direct illumination, no matter the colour, will fog paper faster than indirect, diffused illumination. The reason is partly geometry: a diffuse source spreads photons across a wider area, lowering the intensity per square centimetre. The other reason is wavelength. Sodium vapour lamps, which emit a narrow yellow band around 589 nanometres, are sometimes used in older commercial darkrooms because that band falls in a low-sensitivity region of most black-and-white papers. For colour work, the rules tighten dramatically. Colour paper is sensitive across the visible spectrum, so dedicated colour darkrooms operate in total darkness or under very deep green filters of specific densities.

Australian darkroom educators at institutions like RMIT in Melbourne or Sydney TAFE typically require students to perform a coin test before trusting a safelight. Place a coin on a sheet of paper, expose the sheet to the safelight for the longest you might leave it on the easel, then develop it. If a ghost of the coin appears, the safelight is fogging the stock. That simple physics experiment has saved countless prints from unwanted density.

Optics of the Enlarger: From Negative to Print

The enlarger is a projection system, and the laws of optics that govern it are the same laws that govern any camera. A condenser head focuses light through the negative with a relatively even, slightly contrasty spread, while a diffusion head, with its frosted glass or integrating sphere, scatters the light across a wider, softer cone. Both produce images, but the visual signature of the print differs. Condenser heads tend to make dust and grain more visible, while diffusion heads tend to soften them.

Magnification matters because illumination falls off with distance. A print made at four times linear enlargement receives roughly one sixteenth of the light per square centimetre that an eight times enlargement receives, because light intensity obeys an inverse square relationship. That is why exposure times increase dramatically as a 35-millimetre negative is blown up to a 16 by 20 inch print. Photographers compensate by raising the lens aperture, using a more powerful lamp, or simply extending the timer.

Lens choice also influences the print. A well-corrected enlarging lens, designed for flat-field projection, will render a square grid as a square grid at the edges of the easel. A poorly corrected lens will bow the lines outward, producing a pillow-shape distortion. In community darkrooms from Surry Hills to Fitzroy, the optical quality of the enlarger lens is one of the first things to check when prints start to look soft or warped at the margins.

Exposure, Reciprocity, and the Latent Image

At the moment of exposure, a photon strikes a silver halide crystal and transfers its energy to an electron trapped at a sensitivity speck within the crystal. That electron migrates to a positively charged interstitial silver ion, forming a small cluster of four or more silver atoms known as the latent image. The latent image is invisible to the eye, but during development it acts as a catalyst, allowing the entire crystal to reduce to metallic silver in a fraction of a second. Without that initial photon, no development occurs, and the crystal washes away in the fixer.

Reciprocity is the principle that exposure is the product of intensity and time, and for most enlarger work it holds true. A print exposed for ten seconds at f/8 should look identical to one exposed for twenty seconds at f/11, since both combinations deliver the same total amount of light. The principle breaks down at the extremes. Very long exposures, of a minute or more, lose effectiveness because silver halide grains become less responsive over time. Very short exposures, of a fraction of a second, lose effectiveness because individual grains have not had time to capture a second photon. Printmakers exposing Ilford Warmtone at high magnification in a dim Sydney studio often find their test strips running slightly under-exposed at the ends, a classic reciprocity failure.

Stopping down the lens sharpens the print but lengthens exposure. Choosing a contrast grade filters the spectrum rather than the brightness. Choosing the paper surface, glossy, pearl, or matt, changes how the developed silver reflects light back to the viewer. Each of these is a lever on the physics of how light meets chemistry.

Working With Light: Habits for the Printmaker

A working darkroom rewards small, repeated acts of measurement. The following habits are drawn from printmakers working in shared Australian facilities, where equipment, paper stocks, and chemicals vary from session to session.

Light is the medium and the message in the darkroom, and learning its physics is what separates a printmaker who reacts to negatives from one who reads them. Meg Turner's work, from her New Orleans studio to collaborative projects further afield, treats that reading as a daily practice. Browse the print portfolio, sign up for a workshop, or get in touch about contract printing — the enlarger is on, and the timer is running.