"Histoires courtes": photography and electronic detectors

"Histoires courtes": photography and electronic detectors

On Monday documentary filmmakers Jean-Francois Dars and Anne Papillaut published a short “film” that they made about my research and photography here.  Here is a direct link to the film.
It was wonderful working with them. It was a long process: we started in April when we recorded the soundtrack. I had carefully prepared a text. But it didn’t work at all! Faced with the microphone I couldn’t recite any of the words at all. I was completely stuck. So I just started talking about what I wanted to say in french, because it seemed easier to speak to them in French about these things (I speak in French with all of my french friends and colleagues, after all it is more than ten years that I am living here now). And that was the text that they used.

Taking the photographs 

Afterwards, during the summer Jean-Francois came to my office and took a few photographs and after thata we went into the darkroom where I developed a big picture of one of the Euclid CCDs. Jean-Francois suggested that we take some pictures at night, because I had talked about how I preferred taking pictures at night on film, so a few months later we spent a wonderful winter evening together (after a nice meal of course) when we walked around the centre of Paris and took pictures.

See the craters of the moon

Or rather, I took pictures and Jean-Francois took pictures of me taking pictures. I can’t say that I approached this with some small amount of trepidation, because Jean-Francois was a friend of Kertesz, and Kertesz took the first-ever photographs of Paris at night! However, in the end I was quite happy with the photographs I took and a selection of them are on my 52rolls pages. If you look carefully, you can see Jean-Francois taking pictures of me. It was so easy to interact with people and take these pictures, it was the most natural thing in the world. I just applied my Winogrand-inspired technique of smiling a lot, even when I wasn’t sure if anyone was looking at me or not. This really does work.

Losing the photons

The “histoires courtes” are very short, most I think are under three minutes. The text and discussions were edited to focus on the key difference between electronic detectors and photographic plates: the quantum efficiency of silver grains is a lot lower than electronic detectors. In the visible spectrum, the latest CCD cameras from e2v have a quantum efficiency in the visible bands of almost 100%. Only around 4% of photons falling on film get converted into silver grains. This difference of course had some interesting consequences: in the film era, people spent a lot of time and energy trying to increase the quantum efficiency of photographic plates, “sensitising” them by baking them in the oven and so forth. Eventually photoelectric detectors came along, but alas, they were not array detectors and so making images was impossible. The arrival of electronic array detectors was a revolution: a CCD camera suddenly transformed a 2 metre telescope to a 4 metre telescope. Now today with the very high efficiency of electronic detectors in the visible bands, the only way to increase the number of electrons is to increase the size of the primary mirror. In addition to the greatly increased sensitivity of electronic detectors offer much higher angular resolution, and in most cases the electronic detectors fully sample the instruments’ response function, so the amount of detail you can record is limited by the atmospheric conditions and not the detectors. So the advantages of electronic detectors are clear for astronomers. But for photographers?

And on film?

I already wrote about this over on Leicaphilia. To take a good picture on an average day in Paris, you need an detector sensitive to say ISO400, a lens that can do f8 and a shutter speed of 1/125s. Nothing more. Most digital cameras have been able to do this for at least a decade and a half. And if you want to print your masterwork at a reasonable size – 18×24 say – in most cases ~5 megapixels suffices. Nothing more. So, you might wonder, where does that leave the last decade-and-a-half of technological development? Well, not in the service of taking pictures…

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