Flare veil

Lifted from Break/Fix — unexpectedly soft images and wrong reciprocity corrections, case 5, with the flare pair from commissioning the pinhole camera.

What you see

Correct overall density, flat grey shadows, clean highlights. The negative is not thin and it is not dense; it is short. The scale has been compressed at the bottom.

The decisive observation is where the veil stops. It stops at the strips that were under the paper stops, because flare came through the hole and therefore ends at the edge of the image circle. That single fact separates it from every leak and from safelight fog, both of which carry on under the stops.

Likely causes

1. A bare-wood, foil-lined or light-coloured interior.
2. An unblackened pinhole plate, whose inside face is a small mirror parallel to the film.
3. A bright source just outside the frame. A source close to the frame edge is worse than one well outside it, because it strikes the wall at a shallower angle and closer to the film.

What is happening: the chemistry and physics

A hole cannot select. Light arriving at an angle greater than the frame’s own half angle passes through the hole exactly like the light that makes the picture, and lands on the interior walls rather than on the film. A matt black wall absorbs most of it; a shiny one returns it, and what returns is spread more or less evenly over the whole frame.

A constant addition of exposure is negligible where the picture already delivered a lot of light and dominant where it delivered almost none. So the shadows lift and the highlights barely move. The toe compresses, and the contrast of the whole picture falls.

That is why flare is a contrast fault rather than a density fault, and why it is diagnosed by looking at the place on the sheet where the picture should have been at its darkest and asking whether it got there.

Diagnostic questions

• Does the veil cross the paper-stop strips? No means flare. Yes means a leak or fog.
• The flare pair. Photograph the same scene twice with a bright source just outside the frame, once with and once without a card flag held out of frame on the source side, at the same computed exposure. If the flagged sheet has cleaner shadows, the camera is adding flare. This is the confirming test and the commissioning session already built it.
• The torch test. A torch inside the camera in a dark room. Anything that shines is a candidate.
• Is the control sheet clean? If the control is clean and the picture is veiled, the fault is inside the camera.

!Four things lift the shadows and two questions separate them

Flare, a leak, safelight fog and an exhausted or oxidised developer all flatten a negative from the bottom up. Two questions do the work.

Does it cross the strip under the paper stop? Flare does not. The other three do.

Is it on the unexposed control sheet? Safelight fog and a bad developer are; flare and a leak are not, because the control never went in the camera.

Corrective action

Matt black paint first, then flocking or black felt on the two walls that face the film most directly, and a blackened pinhole plate on both faces, not just the outside.

A flag on the source side, out of frame, for any exposure with a bright source near the edge of the field.

A negative already veiled can be printed on a harder grade, which restores contrast without restoring the shadow separation that was never recorded.

Prevention

Test the flocking rather than assume it. Two identical inserts for one wall, one painted and one felted, and one scene photographed twice, is a controlled comparison that costs two sheets and settles the question for the life of the camera.

Blacken every new pinhole plate on both faces as part of making it, and record in the plate register that you did.