Loading paper and sheet film into a pinhole back

Purpose

To put one sheet into the back — flat, the right way round, in the right place — and get it out carrying no exposure but the one you gave it.

When to use it

Every sheet through the camera built in Part VI: a paper negative in the flat back, a sheet sprung into the curved insert, a tin loaded against its lid, or sheet film in a double dark slide. It runs from the packet opening to the loaded back reaching its light-tight box, and in reverse.

It does not choose the exposure — exposure and reciprocity correction does. On site the outdoor session takes over; afterwards, film processing.

Before you start

You should already know which back you are using and its measured focal distance, from the build, and your measured safe working time, from handling paper in dim light. ILFORD’s ceiling for MULTIGRADE RC papers is four minutes of direct safelight at not less than 1.2 m, and your figure from the safelight test replaces it downwards. Film gets no safelight: ILFORD instruct total darkness for FP4 Plus, FOMA infrared or total darkness for FOMAPAN 100.

On the bench: the back and its dark slide; the packet in its box; a light-tight box; a straight-edge; a pencil; a knife on a swept mat; tape and clips for the tin and the curved insert. Rehearse in the light before working in the dark, as ILFORD instruct for a film spiral: every route below is done by feel.

Level A on the classification rubric: dry coated articles, nothing weighed, dissolved or heated, no liquid waste. The hazards are the knife and moving about in a dark room.

Procedure

The room and the bench

1. Prepare the room by handling paper in dim light: prove it dark, cover every other emitter, safelight at its tested distance. Loading film, switch the safelight off.
2. Dry the bench, wash and dry your hands, and lay out in a fixed order — box left, back in front, light-tight box right. Nothing moves once the light is off.
3. Check the empty back — stops clean, pressure-plate foam unbroken, felt in the slot, no grit.

Paper into the flat back

4. Settle which face is the emulsion in the light, on an offcut: the shinier face, which curls concave. Write it on the box.
5. Cut sheets a few millimetres larger than the stop aperture each way and small enough to drop in unforced. Write the cutting size on the back.
6. Open the box and bag with the opening away from the lamp, take only the sheets this run needs, count them, and close both again.
7. Lay the sheet behind the stops, emulsion side facing the pinhole, seated at all four edges.
8. Fit the pressure plate and lay the straight-edge across the loaded back. It must lie flat.
9. Push the dark slide home to its index line.
10. Pencil a mark on the slide’s outside showing which corner is top-left as the camera sees it, and put the back straight into the light-tight box.

The curved insert, and the tin

11. In the curved insert, spring the sheet against the inside of the skin, emulsion facing the axis, and clip both ends. Fibre paper takes a 50 mm radius more willingly than resin-coated paper.
12. A tin has no dark slide: load against the stops in its lid, close it, tape the joint, and keep the shutter shut until the camera stands where it will expose — one sheet per darkroom visit.

Sheet film into a holder

13. Lights out. No safelight, and no glance at a phone.
14. Take one sheet and find the notch. FOMA state it sits at the right upper corner of the short side of the format, so with the notch at the top right the emulsion faces you. Check your own box’s diagram: the course has not established that convention as universal.
15. Slide the sheet under both rails, emulsion outwards, seated at both edges.
16. Push the holder’s dark slide home, unexposed face outwards. Where a holder is unmarked, adopt one convention and write it on the holder.
17. Close the holder into the spring back so it bears on its own light-trap ridge, square and untwisted. The holder seals itself; hold it flat without distorting it.

On to the camera, and off again

18. Fit the back, then confirm the shutter is closed by looking, not by remembering.
19. Withdraw the dark slide only now.
20. Expose. Then close the shutter, push the slide fully home, and only then lift the back off — in that order, every time.
21. Carry the loaded back covered, in its light-tight box.

Unloading

22. Unload in the light you loaded in: the tested safelight for paper, darkness for film.
23. Label each sheet’s back in pencil before it leaves your hand — number, date, the corner from step 10 — holding it by the edges.
24. Put exposed sheets straight into the light-tight box or a sealed enclosure, never a pile on the bench.
25. Count and close: sheets out equals sheets exposed plus sheets returned, and unused paper goes back into its original package, as Kodak instruct, before the white light.

How you know it worked

• The straight-edge lay flat at step 8, and the slide reached its index line without force.
• The frame you composed is the frame on the sheet: no edge is cropped.
• Borders process white, and any fog band has an edge you can name, because step 10 recorded which corner was which.
• A control sheet, loaded and unloaded in the dark and never near the camera, processes to base fog.

If a step fails

Step 1, the room will not go dark. Load and unload in a changing bag until the leak is found: every route here is done by feel.

Step 4, you cannot tell which face is the emulsion. Do not guess: expose and process an offcut one way up, and mark the answer on the box.

Step 8, the straight-edge rocks. The sheet is bowed, so the middle of the frame has a shorter focal distance than its edges: thicker foam, or a second leaf spring. Read buckled-sheet softness.

Step 9, the slide will not seat. Something is proud — a lifted stop, a corner outside the stops, grit in the felt. Do not force it; reload.

Step 14, the notch is missing or unfamiliar. Your own box’s diagram governs. With none, spend one sheet in the light learning the pattern.

Step 19, the slide came out with the shutter open. The sheet holds an exposure you did not give it: treat it as a test strip.

Step 20, the slide jams on its way home. Cap the pinhole first, then work it.

One edge is fogged after processing. Compare against the commissioning sheets before blaming the loading: a band along a seam is an edge leak, a band at the slot is the dark slide, an even veil the box or the room.

What to record

One line per sheet on the exposure log: date; the material and its batch; which back and configuration, with its measured focal distance; the pinhole plate; the light you loaded under and the time from packet to box; the corner mark from step 10; sheets out against sheets back. Add a register line whenever a back is altered — new foam, a re-cut stop, a re-made slide.