Halation

Halation

Halation was, at one time, the bugbear of against-the-light photography. It wrecked the images that flare didn’t… As it doesn’t happen with digital, maybe some explanation is necessary. Here goes.
Film isn’t completely opaque, so light can go straight through the emulsion, and then reflect around between the emulsion layer and the backing material, whether it’s film or glass. It’s easiest to imagine the effect with a sheet of glass, which has significant thickness: as the light bounces back and forth between the back of the emulsion and the opposite surface of the substrate, it spreads out.

In other words, it’s a soft-focus-like spreading out of highlights Awful if you’re aiming for technically accuracy, but capable of being quite beautiful with the right shot and the right film. Light and airy and lovely.
And there’s a way to kill it – or, at the least, cut it down a good deal. Applying a light-absorbing dye layer to the back of the film does the job nicely, and in some cases, this is obvious in processing: the dye stains the developer and it comes out a very different colour from how it went in – not just a little bit brown!

The best-known example of a film that suffers from halation is the much-lamented Kodak High Speed Infrared black-and-white film. It achieved a considerable following from those willing to put up with temperament in their emulsions – both exposure and development were challenging, I found. Maybe the most famous exponent was Simon Marsden, who used HSIR for pictures of haunted castles, but I found Kathy Harcom’s gentle landscapes, often hand-tinted, were magical. Marsden died several years ago, but KH is alive and well, it seems.

Halation has most of the same characteristics as flare, but is more localised, as it’s an effect that relies on light spreading through the emulsion, rather than bouncing around in front of the film (or sensor). Because a sensor is utterly different in construction and operation from film, it just doesn’t happen in digital imaging, although I suspect that it’s relatively easy to replicate in digital processing (that’s an invitation to the clever processors to tell us all how…)

EfKe, now defunct, produced an infrared emulsion that replicated HSIR’s characteristics – I bought two or three rolls, but didn’t use them all… Maybe the remaining roll will entertain me in the Spring. I found a satisfactory alternative for my own work in Rollei 80S, not a true infrared emulsion, but with extended red sensitivity that gives the pale skin tones that I particularly like from this kind of material. But halation is as well controlled as on any normal modern film.