Outdoor exposure session

Purpose

To make an exposure in daylight and come back with the material unspoiled, the time you actually gave it, a description of the light you could match in another season, and no more solar ultraviolet than the work needed.

When to use it

Every exposure whose light source is the sun: the unfixed silver photogram and the cyanotype photogram in Part I, every pinhole sheet exposed outdoors in Part VI and Part VII, and any contact print made in sunlight instead of under a lamp.

It does not decide what exposure to give — that comes from the material’s own page — and it ends indoors, where film processing, a wash or a light-tight envelope takes over.

Before you start

You should already have a starting exposure or a bracket to run, and know how to load the material — in dim light where it needs it. A maker’s daylight table has a stated window: Kodak give theirs from two hours after sunrise to two hours before sunset, and outside it the table is optimistic.

Packed: the loaded holder or contact frame; an opaque card larger than the frame, and tape; a timer readable in bright light; notebook and pencil; the light meter, if you use one; drinking water; and a hat, sunglasses and sunscreen.

Level A on the classification rubric: nothing is weighed, dissolved or heated, there is no liquid waste, and the only energy source is the sun. The hazards are solar ultraviolet, and the ground you stand on.

Sun protection is the protective equipment here, and ICNIRP’s numbers set it: a brimmed hat with sunglasses gives an ocular exposure factor of 0.02 against 0.5 for sunglasses alone; most summer clothing has a protection factor above 10; SPF 15 to 30 goes on what is left uncovered, every two hours.

Procedure

Before you leave

1. Read the day. Check the ultraviolet index forecast and keep the session out of the four hours around solar noon, which carry the greatest risk. Where the light must be that strong, shorten your time outdoors, not the sheet’s.
2. Rule up the log before anything is loaded; an unrecorded time is an exposure you make again.
3. Dress before you load: hat, ultraviolet-blocking sunglasses, long sleeves, sunscreen on hands, face, neck and ears.
4. Load or build the work indoors under the light that material needs, with clean dry hands and sheets held by the edges. Lay the opaque card over it, taped at two corners; it stays on until the timer starts.

On site

5. Set the work down flat and stable, or the tripod back from any edge, off wet rock and loose ground, clear of a passing width.
6. Look at what is underfoot: concrete, dry sand and surf raise the dose reaching you, and fresh snow nearly doubles it. Where there is a choice, stand on the darker ground.
7. Record, before you uncover: date, clock time, the sky in fixed words — clear, no cloud; thin high cloud, sun visible; broken cloud, sun in and out; overcast, sun not visible — the ultraviolet index if your service publishes one, whether your own shadow is shorter or longer than you are, and any meter reading with the mode it was taken in.
8. Put the sun behind you and keep it there. Never sight it along the camera’s axis or through any optic: NASA state that viewing the bright sun through a lens, binoculars or a telescope without a purpose-made solar filter causes instant severe eye injury, and that ordinary sunglasses are not solar filters.
9. Lift the card and start the timer in one movement. Write the start time down now.

While it runs

10. On a first run of any new material, expose a bracket and not a picture, sliding a mask band by band on the times that material’s page gives. Makers quote sunlight ranges as wide as Jacquard’s one to thirty minutes; one guess inside that lands nothing.
11. Wait in shade and watch the clock, not the material.
12. Where the sky is changing, meter again at the end and log the light as a range with two timestamps. Broken cloud is not a smaller dose than clear sky: breaks in the cover can raise the ultraviolet to clear-sky levels or above.
13. Replace the card, then stop the timer, in that order. The seconds belong to the covering.

Coming back

14. Check the site before you leave: nothing light-sensitive left behind, no tape or card litter, all glass accounted for. Carry the work back covered and out of the sun.
15. Unload in the same light you loaded in, and put anything still light-sensitive straight into its light-tight box or envelope first.
16. Write the log line now, while the sky you are describing is still outside the window.

How you know it worked

• The card went on before the timer stopped, and the two logged times differ by the exposure you meant to give.
• Every row carries a sky description in the same four phrases, so two sessions can be compared at all.
• Sheets carried out equals sheets exposed plus sheets carried back, and nothing came home uncovered.
• No sunburn — a verdict that arrives late. ICNIRP define the minimum erythemal dose as the exposure producing just perceptible reddening 8 to 24 hours afterwards, so redness tomorrow morning is today’s session speaking, and it changes the next one’s hours.

If a step fails

Step 1, the only free hour is the middle of the day. Keep the session and cut your own exposure: work from shade, set up and retreat, and treat the window as a reason to be quick.

Step 4, wind lifts the card before you are ready. Weight it, or clip the sandwich shut and carry it out closed. Do not hold it by hand, which puts your hand in the exposure.

Step 7, no ultraviolet index is published for your area. Use the shadow rule: ICNIRP give it as the simple test for an index above 4 — a shadow shorter than you are means precautions matter, and the shorter it is the stronger the ultraviolet.

Step 9, the timer was not started, or was started late. Do not estimate: cover the work and treat the sheet as a test strip, not a result.

Step 12, cloud crosses during the exposure. Log it as a fraction of the total — “clear for two minutes of six, thin cloud for four” — and expose a second sheet when the sky settles.

Step 13, you stopped the timer before covering. The extra seconds are real: add them from the clock and mark the figure as an estimate.

Step 15, a sheet was uncovered in daylight by accident. Do not put it back in the packet: mark it, process it alone, and read what it did before spending more on that box.

What to record

One line per exposure, in the notebook or the printable exposure log: date, clock time at start and stop, the material and its batch, the sky in the fixed phrasing, the ultraviolet index or the shadow verdict, any meter reading with its mode, the exposure given, and whether the sky held for all of it. Where you ran a bracket, add the cumulative time against each band and one sentence naming the band you chose and what it cost you.