In July, I had the great luck to visit the Kennedy Space Flight Center to see the launch of the Euclid satellite. I wrote this a few days after the launch, but with the great amount of work that we have all been doing since then, I have not had time to publish this! I was thinking I had better get caught up…
My trip to Florida started inauspiciously enough, with a text message telling me that my flight to Newark, the first leg of my journey, had been delayed. This meant that I would miss my connection to Orlando. At CDG the united staff told me that, although they couldn’t rebook my flight from Paris, don’t worry, in Newark they will look after you. I imagined disembarking from the plane and walking right to the smiling United representative at the service desk who would immediately put me on the next available flight. The reality was a four-hour wait in the line-up at Newark until finally a very helpful lady booked me on a flight to Orlando the next morning. I arrived in the humid Florida heat on Friday with enough time to pick up my tickets and those of my colleagues. I will pass in silence over the night spent in a hotel in the grey post-industrial suburbs of New Jersey.
I admit that I had a certain ‘frisson’ seeing the signs for ‘Kennedy Space Flight Center’ (KSFC) as I drove away from Orlando airport. As a child in Ireland in the 1970s I wrote to KSFC and asked them to send me stuff about space and planets. Soon enough, a big wad of old press releases as well as some nice colour pictures of planets arrived from America in a big yellow envelope. It was wonderful. I couldn’t understand why more people were not interested in astronomy given the Universe was so large and the Earth was so small. And so now, 40 years later, I was on a highway heading right to KSC. Soon enough, I was flying over a large river inlet and in the distance I could see what I knew was the famous Vehicle Assembly Building, the largest building in the world. But right now, I was not going to KSC, I was only going to the hotel to get the tickets…
The next morning, I left the hotel at 07:20. The launch was scheduled for 11:12AM, but I knew that My bag was full of cameras and factor 50 sunscreen. I had a big hat I bought at the surf shop near my hotel, ready for the intense heat and light of a summer morning in Florida. I picked up a colleague at his nearby hotel.
Although we had left early, there were already many people at Kennedy for the launch. It was blisteringly hot, and the sun shone brightly in a blue sky without clouds. Although I have been working on the Euclid project for more than a decade and have been to every consortium meeting (except one), there were many people I had never seen before.
Soon enough, we left on the first bus carrying everyone to the bleachers at banana creek, a prime viewing location across the water from the launch towers. The bleachers, however, had not an inch of shade, and it was more than an hour until the launch; no question of staying outside. But next to the bleachers was the Saturn V Apollo building, and we spent a good hour there looking at this impressive space hardware from the past. Soon it was time to go outside again
At the bleachers, everyone was finding their places. There was blinding heat and light. To the right, there was a big screen relaying the SpaceX/ESA livestream, and a local commentator provided us some additional context. I stared out at the horizon at where the Euclid will soon leave the Earth. Confusingly, there were several different launch towers.
And suddenly, we were only a few minutes before launch. We were in the bleachers. I had promised to do a livestream with IAP auditorium where everyone was gathered to watch the launch. I put in my AirPods and my colleague Amadine tried to film me with my iPhone. There was so blinding light everywhere it was impossible to see the screen, but I could hear the questions from Paris and I tried to formulate some intelligent answers.
We were in the final minutes before the countdown. No sign of a hold or a delay. There were no clouds in the sky. We were told there was a delay between the livestream and the real world, a few seconds, not much but enough to make everyone chanting countdown pointless. We didn’t know the real-world number of minutes left. Suddenly, there was an enormous cloud on the horizon, low down, and rising from the clouds we could see the Falcon 9 rocket atop a bright orange-yellow flame. It was one of the brightest things I have ever seen. But at first it was completely silent as the rocket arched up into the sky. Then the sound came, a great rolling rumbling wave of sound energy. My cheap straw hat vibrated in time to the roar of the nine merlin rocket engines. Clearly, it takes a lot of energy to get a one-ton rocket to L2, I thought to myself.
I was transfixed. In the bag at my feet I had my two Leica cameras, I had my telephone and a Ricoh compact camera too, but I didn’t want to do anything but look at this bright orange candle as it disappeared into the cloudless sky. On the callout from the screen we heard ‘maxq’ indicating the rocket had passed through the zone of maximum aerodynamic pressure. And then, it was gone, and there was finally just a cloud in the sky, a cloud of water vapour made by the Falcon 9 rocket.
The livestream from ESA and SpaceX continued. We saw the booster coming back, landing on the drone ship. There in orbit was a short coast phase and the second stage ignited again. By this time, all the public had left and there were only a few of us in the bleachers or sheltering nearby. Then, on the “jumbotron” — the big screen they have there — we saw Euclid deploy, the silvery yellow foil catching the sunlight as at it separated from the SpaceX second stage. But still, the story was not over. Was the satellite alive and communicating with the Earth? Then finally on the screen we saw the first signal from the spacecraft. Euclid was alive and heading to L2. And the real work would start very soon.
The road to the space coast (looking back on the ideas that led to Euclid)
On Florida’s Space Coast, the Euclid satellite is undergoing the final preparations for launch on a Falcon 9 rocket next Saturday, July 1st at 11:12 EDT. Although the Euclid mission was approved by ESA in 2011, the origins of the project date back more than a decade before that, starting with the realisation that the expansion of the Universe is accelerating.
In cinema, great discoveries are usually accompanied by the leading lights throwing their hands in the air and exclaiming, “This changes everything!” But in real life, scientists are cautious, and the first reaction to any new discovery is usually: is there a mistake? Is the data right? Did we miss anything? You need to think carefully about finding the right balance between double-checking endlessly (and getting scooped by your competitors) or rushing into print with something that is wrong. At the end of the 1990s, measurements of distant supernovae suggesting the accelerated expansion of the Universe were initially greeted by scepticism.
Conceptually, what those measurements were saying was simple: the further away an object is, the faster it is receding from us. Edwin Hubble’s early observations of galaxies demonstrated that there was a straight-line relationship between the distance of an object and the speed of movement. The most simple explanation (although one that scientists took a while to accept) was that the Universe was expanding.
Over the next few decades, researchers embarked on a long quest to find different classes of objects for which they could estimate distances. Supernovae were one of the best: it turned out that if you could measure how the brightness of supernovae changed with time, you could estimate their distances. You could then compare how the distance depended on redshift, which you could measure with a spectrograph. Wide-field cameras on large telescopes allowed astronomers to find supernovae further and further away, and by the end of the 90s, samples were large enough to detect the first tiny deviations from Hubble’s simple straight-line law. The expansion was accelerating. The origin of the physical process of expansion was codified by “Lambda”. Or “dark energy”.
But those points on the right-hand side of the graphs which deviated from Hubble’s straight-line law had big error bars. Everyone knew that supernovae were fickle creatures in any case, subject to a variety of poorly understood physical mechanisms that could mimic the effect that the observers were reporting.
Initially, there was a lot of resistance to this idea of an accelerating Universe, and to dark energy. Nobody wanted Lambda. Not the theorists, because there were no good theoretical explanations for Lambda. And not the simulators, because Lambda unnecessarily complicated their simulations. And not even the observers, because it meant that every piece of code used to estimate physical properties of distant galaxies had to be re-written (a lot of boring work). Meanwhile, the supernovae measurements became more robust and the reality of the existence of Lambda become harder and harder to avoid. But what was it? It was hard to get large samples of supernovae, what other techniques could be used to discover what Lambda really is? Soon, measurements of the cosmic microwave background indicated that Lambda was indeed the preferred model, but because the acceleration only happens at relatively recent epochs in the Universe, microwave background observations only have limited utility here.
Meanwhile, several key instrumental developments were taking place. At the Canada France Hawaii Telescope and other observatories, wide-field cameras with electronic detectors — charge coupled devices, or CCDs — were being perfected. These instruments enabled astronomers for the first time to survey wide swathes of the sky and measure the positions, shapes and colours of tens of thousands of objects. At the same, at least two groups were testing the first wide-field spectrographs for the world’s largest telescopes. Fed by targets selected from the new wide-field survey cameras, these instruments allowed the determination of the precise distances and physical properties of tens of thousands of galaxies. This quickly led to many new discoveries of how galaxies form and evolve. But these new instruments would also allow us to return to the still-unsolved nature of the cosmic acceleration, using a variety of new techniques which were first tested with these deep, wide-field surveys.
In the 1980s, observations of galaxy clusters with CCD cameras led to the discovery of the first gravitational arcs. These are images of distant galaxies which are, incredibly, magnified by the passage of light near the cluster. The deflection of light by mass is one of the key predictions of Einstein’s theory of general relativity. The grossly distorted images can only be explained if a large part of the mass of the cluster is concealed in invisible or ‘dark’ matter. However, in current models of galaxy formation, the observed growth of structures in the Universe can only be explained if this dark matter is distributed throughout the Universe and not only in the centres of galaxy clusters. This means also that even the shapes of galaxies of the ‘cosmic wallpaper’ throughout the night sky should be very slightly correlated, as light rays from these distant objects pass close to dark matter everywhere in the Universe. The effect would be tiny, but it should be detectable.
Around the world, several teams raced to measure this effect in new wide-field survey camera data. The challenges were significant: the tiny effect required a rigorous control of every source of instrumental error and detailed knowledge of telescope optics. But by the early 2000s, a few groups had measured the ”correlated shapes” of faint galaxies. They also showed that this measurement could be used to constrain how rapidly structures grow in the Universe. At the same time, other groups, using the first wide field spectroscopic surveys, found that measurements of galaxy clustering could be used to independently constrain the parameters of the cosmological model.
Halfway through the first decade of the 21st century, it was beginning to become clear that both clustering combined with gravitational lensing could be an excellent technique to probe the nature of the acceleration. Neither method was easy: one required very precise measurements of galaxy shapes, which was very hard to do with ground-based surveys which suffered from atmospheric blurring; the other required spectroscopic measurements of hundreds of thousands of galaxies. And both techniques seemed highly complementary to supernovae measurements.
In 2006, the report from a group of scientists from Europe’s large observatories and space agencies charted a way forward to understand the origin of the acceleration. Clearly, what was needed was a space mission to provide wide-field high-resolution imaging over the whole sky to measure the shapes, coupled with an extensive spectroscopic survey. Both these ideas were submitted as proposals for two satellites: one would provide the spectroscopic survey (SPACE) and the other would provide the high-resolution imaging (Dune). The committee, finding both concepts compelling, asked the two teams to work together to design a single mission, which would become Euclid. In 2012, the mission was formally approved.
Euclid aims to make the most precise measurement ever of the geometry of the Universe and to derive the most stringent possible constraints on the parameters of the cosmological model. Euclid uses two methods: galaxy clustering with the spectrograph and imager NISP (sensitive to dark energy) and gravitational lensing with the imager VIS (sensitive to dark matter). Euclid‘s origins in ground-based surveys makes it unique. Euclid aims to make a survey of the whole extragalactic sky over six years. But unlike in ground-based surveys, no changes can be made to the instrument after launch. After launch, Euclid will travel to the remote L2 orbit, one of the best places in the solar system for astronomy, to begin a detailed instrument checkout and prepare for the survey.
I have been involved in the team which will process VIS images for more than a decade. The next few weeks will be exciting and stressful in equal measures. VIS is the “Leica Monochrom” of satellite cameras: there is only one broad filter. The images will be in black-and-white. It will (mostly) not make images deeper than Hubble or James Webb: Euclid‘s telescope mirror is relatively modest (there are some Euclid deep fields, but that is another story). But to measure shapes to the required precision to detect dark matter, every aspect of the processing must be rigorously controlled.
VIS images will cover tens of thousands of square degrees. Over the next few years, our view of the Universe will dramatically snap into high resolution. That, I am certain, will reveal wonders. Those images will be one of the great legacies of Euclid, together with a much deeper understanding of the cosmological model underpinning the Universe that will come from them and the data from NISP.
This Thursday, I’ll be travelling to Florida to see Euclid start its journey to its L2 orbit for myself. I’ll be awaiting anxiously with many of my colleagues for our first glimpse of the wide-field, high-resolution Universe that will arrive a few weeks later.
Tim Vanderweert, author of the Leicaphilia.com blog, left us last week. I couldn’t let Tim’s passing go without comment: like many people, I owe him a lot.
About a decade ago, just after the death of my father (I am sure these events were linked), I started taking photographs and photography more seriously. More intentionally, at least. Some mysterious path led me to film and Leica rangefinder cameras. The first time I held a Leica rangefinder was in a second-hand shop on the boulevard Beaumarchais, and that camera is still the camera I have with me almost every day. But what was going on? Like we do today I searched the internet to understand, and soon enough I came across Leicaphilia.
A revelation! Leicaphilia was easily the most lucid, funny and opinionated website about film, Leica cameras and photography on the internet. The mysterious site administrator was well aware of all the contradictions of using such cameras today. A relief: most photography web-sites take themselves much too seriously. Soon after (January 2016), I wrote an email to Leicaphilia and sent through an article that I though might fit into the Leicaphilia ethos. I was surprised and happy when I received an almost immediate response from the admin (whom I learned was called Tim V) telling me that he’d be happy to run my article in a few weeks.
When I learned later that year that Tim was coming to Paris, I invited him to visit our institute and to come for espresso in my office. In person, Tim turned out to be like you’d expect from reading Leicaphila: immensely knowledgable, opinionated and cultured. But also very generous and encouraging. I showed him around where I work, and we visited the old Observatory buildings. We even got into the normally-closed museum of astronomical instruments after I told the observatory staff that Tim was a visiting specialist of rare optical instruments (which is true!).
Tim met my colleagues and at the end we had espressos once again this time on the IAP terrace. It was a thoroughly enjoyable afternoon. When I told him about my film-developing technique, he arranged for a pack of Diafine developer to be hand-delivered to my office by relatives who were visiting Paris. They came for coffee too, and coincidentally it was a day that we had birthday cake in the office. A big party ! It was a revelation seeing what my rolls of Tri-X looked like in Diafine. In emails since then, Tim promised to keep my in Diafine indefinitely.
Over the next years, I followed Leicaphilia closely. There was no place on the internet you could find such abstruse, challenging and funny content. Tim was trying to work out what all this stuff meant, where photography was going, or not, and it was great to follow along on his journey. Then there were the excellent take-downs of crooks and charlatans like that time he found the mugshots and police records of a couple of scammers who were selling ”black paint” Leica cameras. I was amazed he was able to write so much given that many of the articles seemed to be so deeply researched and knowledgable. Somewhere in there, Tim activated commenting on the site, and those comments were a revelation: it turned out that there was a community of civilised, intelligent people following the site who could have a meaningful conversation without descending into polemic and outrage; very uncommon on today’s internet.
A few times, Leicaphilia went dark or offline: Once Tim was (perhaps) hacked by Scientologist friends of Thorsten O. (frequently a subject of ridicule on Leicaphilia). But often the silences were simply Tim’s centres of interests changing. They made us all realise how much we valued Leicaphilia and how eagerly we awaited Tim’s next idiosyncratic update.
But then, around two years ago after a longer pause, Tim announced he had cancer. I was shocked. It sounded hopeless but after surgery and treatment he recovered and in summer 2021 we met once again in Paris. First at a cafe in the Marais, and then for a meal at our small Parisian apartment. Tim and his wife came as well as two exchange students that they had been hosting at their house. It was a lovely evening. Tim was in great form. He had brought copies of his books for me and we would have talked late into the night if the evening hadn’t been cut short by the results of a faulty COVID test.
For most of the next 12 months, the only update on Leicaphilia was a brief message announcing that Tim was selling his digital Leica. I expected that Tim had been once again zooming around the back roads of North Carolina on his motorcycle. So I was unprepared for the message from Tim in August 2022 telling me that his cancer had returned and this time it didn’t look like there would be an easy escape. I remember around five years ago when I told him I was being treated for a ”minor” cancer (which is now thankfully under control). Tim mentioned that if something like that ever happened to him, he would be frightened. But talking to him after he sent me that message, he seemed more annoyed than frightened. Annoyed that this would happen to him now.
Readers of Leicaphilia know the rest of the story: Tim confounded the doctors by not dying then and there, but living for another four months. And during those four months Leicaphilia was a torrent of posts, often several every day. There was much new material, together with old posts that had been on the shelves. All of them in Tim’s trenchant funny style. He gave so much of the little energy he had left to us, the readers of Leicaphila. He was generous in other ways too: I travelled to the other side of Paris and picked up almost a hundred metres of film that Tim had sent to me via a friend who had been to Tim’s premature ”going-away-party’;.
Leicaphilia was inspirational. In person, Tim was an exceptional character. You don’t meet so many people like Tim in a lifetime. Returning to my apartment the evening after the day Tim died, I found a parcel waiting for me. It was a packet of Diafine that Tim had sent me only a few days before his death. Hail and farewell, Tim, and thanks!
Sometime near the next year or two, hopefully, the Euclid satellite will launch. On-board will be the largest camera ever made for a space mission (although who knows what the spooks and generals have). The entire Euclid optical system has been constructed to produce the most stable, precise and clearest image of the deep Universe: above the murky soup of Earth’s atmosphere image quality is only limited by telescope optics. After launch, Euclid will travel to the solar system’s prime observing spot, a distant place a million and a half kilometres from the Earth. There, the angle of the sunlight falling on Euclid‘s solar panels will be carefully controlled so that the telescope does not expand or contract from the heat of the sun’s rays and therefore, very slightly, defocus the telescope.
But what will Euclid do? At the end of the mission, we will have images covering almost the entire sky not obscured by our galaxy’s clouds of gas and stars. The entire pristine sky right out into the Universe. In those images, there will be a billion faint and distant galaxies. Thanks to the finite speed of light and the fantastic distances of those galaxies, we’ll see them as they were six billion years ago, when the Universe was only half it’s current age.
Between us those galaxies there is the Universe’s invisible scaffolding, a dense web of unknown material — we are calling it Dark Matter for now — which bends light every so slightly. By the time this light reaches Euclid‘s sensitive detectors it will be, ever so slightly, distorted. On an individual galaxy this effect is impossible to see: but averaged over the billions of objects that Euclid will observe, it will provide the most sensitive measurement of how much of this Dark Matter that there was in the second half of the Universe’s lifetime. Coupled with Euclid‘s other instrument, a precise distance-measuring tool, astronomer’s hope to gain some insight into the nature of the force — if it is a force — which is causing the Universes’ expansion to accelerate. To make a new measurement of the geometry of the Universe. Hence the name, Euclid. Worth, indeed, the billion-euro price tag.
But let’s go back. When Lois Daguerre searched for support for the new photographic techniques that he had developed based on the work of Nicéphore Niépce, the astronomer Francois Arago quickly realized the immense potential photography could have for astronomy. Arago arranged for Daguerre’s pension and that the methods he perfected would be made freely available to everyone. For the first time, a permanent, objective record could be made of objects in the night sky. Anyone could analyse the images: never again would a scientific advance be based on a sketch of what someone thought they saw through the eyepiece of a telescope in the dead of night. And before long, the measurement of those images could be handed off to machines, although in those early days maps of the night sky were made by laboriously counting galaxies and stars by hand on thousands of photographic plates.
In the early 1970s, scientists developed the first light-sensitive electronic array detectors, the charge-coupled device (CCDs). In 1976, Janesick and Smith took the first images of astronomical objects with these new highly sensitive instruments. Astronomers were quick to realize the immense potential of CCDs. They were miraculous devices. In astronomy, the most important aspect of a telescope is its light-gathering power — how big the mirror is. The incredible sensitivity of CCDs meant that swapping photographic plates for CCDs meant suddenly that a 2-metre telescope could see objects only accessible to a much-larger 4m-class scope. It was miraculous.
The transition from film to digital for consumer cameras was slower. One year before a CCD camera was first attached to a telescope, Steven Sasson, an engineer at Kodak famously demonstrated the first digital camera to an assembled room of Kodak managers. They didn’t immediately understand why anyone would want to look at an image on a TV screen, but they nevertheless quickly realized the great threat this technology posed to Kodak’s future. Although they allowed Sassoon to continue to work on digital cameras, the orders were to keep them under wraps: they wouldn’t change their minds until it was too late and other companies had successfully brought digital cameras to market. Today, the market for film is one percent of what it was at its peak.
The wave of pixels overwhelmed film cameras in the early 2000s, but even by the early 1990s film photography had almost disappeared from professional astronomy. Emulsions could hold their own against pixels only for huge large images covering large parts of the sky. My Masters’ thesis, a survey of the distant Universe, in fact, relied on data from wide-field photographic plates. But by the turn of the millennium, cameras comprising several detectors joined together became available and the last place where photographic plates were useful in astronomy disappeared. Today, the whole sky has been imaged electronically, and Euclid will provide a revolutionary high-resolution view of the Universe covering most of the sky. This will certainly lead to discoveries not imagined by the telescope planners. No professional astronomer could imagine pointing a photographic plate at the sky and thereby throwing away three-quarters of the photons that crossed half the Universe to get to that photographic plate.
But meanwhile, a strange thing happened. Film photography has refused to die. Sales of film have ceased to decline and companies are working hard to find the right scale at which to produce and sell film. Prices of used film cameras, from disposable point-and-shoot cameras to Leica rangefinders, are steadily increasing. Today, even the pixel-peeping pages of Digital Photography Review runs features about film photography.
Other than the pixels
I have always been interested in photography from when I first took an accidental picture of my own thumb with my parent’s SLR in the 1970s. But in 2015 I felt that I was spending too much time to make images from my digital cameras into something that I felt had some connection to. They seemed plastic and too perfect. I bought a small Olympus XA and then only a month or so after that a used Leica M6TTL at one of the shops on the rue Beaumarchais. Another friend, a professional photographer, very generously gave me his Leica M6 a few years later. He advised me to buy a digital camera if I ever wanted to spend any real money, that would be much better value for money. Today, I am still shooting almost constantly with both cameras.
At the same time, I started to develop film at home, in the kitchen. Since I started I must have tried almost every combination of film and developer. What is wonderful is how each combination can be so different from the others. In the end, a bottle of Rodinal and one of HC110 is good enough for almost anything. Looking at the binders on the shelves here, I see have shot now about 750 rolls of film. Most of them in the streets here in Paris, a difficult thing to do as the city has been photographed so much. After a year since I started, I discovered that there was a darkroom where I work, and I managed to salvage it in the nick of time: I heard later that there were plans afoot to convert it into a storage cabinet. I try to go there at least once or twice a month, or more, to see what I have shot really looks like, because of course looking at an image on a screen is not looking at an image.
I have written about all of this before. I had imagined, back then, when I was starting out, that I would learn what there was to learn about film photography and then switch back to digital: after all film is anachronistic, right?
Two years ago, just as we were coming out of the first wave of the pandemic, I found myself on a certain online auction site looking at cameras. Six months or so without travelling and with the city shut down meant that I felt a little flush with cash. There were one or two cameras out there that I was still a little curious about and which had not been affected by the recent explosive price increases. So I actually bought a digital camera, a Fujifilm XPro-1, and, a week later, a ”’Barnack” Leica, the iiiF, together with a Summitar lens. Average age of both objects: 70 years. Fully functional.
Much has been written about these two cameras on the internet, hundreds of blog articles, there is nothing that I could add here. The XPro-1 is an interesting camera, a simulation of a rangefinder, you can set the shutter speed on a big dial and using one of my Leica-M lenses, the aperture. It can produce instantly crisp images in smooth black-and-white tones. It allows, more or less, taking pictures of the world in a film-photography way (as I explained here). But there is no possible link between that digital image and the darkroom. You take a picture with that camera and it vanishes. It’s dead. What now? I ask myself each time I click the shutter. Despite liking it, I have only taken it out of the house three or four times since I bought it. I am sure it will be useful some time when I have to take pictures in the dead of night to send them around the world minutes later …
But the iiif, now that is an interesting camera. Small and compact. That was from an age when people only put enough in glass in a lens to take a good picture with it printed at normal size, not like today, where lenses are mostly optimised for test charts. When you press the shutter, half of the knobs on the top panel turn instantly, and once again it must be wound forward for the next picture. It certainly cannot be operated with one hand. When I was taking pictures with my Leica M6, someone exclaimed to me ‘That is an old camera!’, to which I replied, showing them the iiif: ‘no, that is an old camera!’. Loading the film requires care, but one quickly learns (I only had problems with one of the forty or so rolls I have shot with it so far).
Soon after buying these two cameras, in early November, it was announced again that we were forbidden to venture no further than 1000 meters from our apartments. Restaurants, bars, and museums were closed. But unlike the first lock-down, this time the parks stayed open. Montsouris is only a few hundred metres from here. This park was created at the end of the 19th century on waste ground filled with tailings from the limestone quarries that were once prevalent in this part of Paris. And there were mice, as the name suggests. A hundred-year-old brownfield site. The next few months I would be confined to the apartment but free to visit Montsouris any time I wished. (Provided, of course, that I didn’t have a Zoom meeting at that time because astronomy continues. There are satellites to launch and research to be done). I soon fell into a routine: I would each a small lunch at midday, and then afterwards I would go for a walk in the park and take my iiif with me. Over the next month or two, I would take hundreds of pictures in Montsouris. Although the parks were open, everyone was wearing masks even outside. After the initial strangeness of this, I soon found it was no fun photographing people because you couldn’t smile at them to let them know that you were non-threatening, an essential thing in a city like Paris. So instead I started talking pictures of dogs.
In astronomy, of course, aesthetics don’t matter. The alignment and arrangement of stars and galaxies on a digital image are not important. It doesn’t look any better if you move the telescope a little to the right. The relevant thing is extracting some fundamental quantitative truth about the Universe from that image. At IAP we have computers filled with hundreds of thousands of images of the sky and our objective is to reduce all that data down to a single table, giving for each object in the image its brightness, distance, mass. Then, compare those tables with predictions of different models to learn what the Universe’s underlying secrets are. And prepare for the immense challenge of doing such a thing with Euclid.
A difficult undertaking all this. What is an object in an astronomical image? With thousands of images, you are not going to look for them one after another yourself. You had better have some way of finding them automatically. You had better be sure that the brightness of the pixels on your images correspond to the real brightness of the objects you’re measuring. A hard problem for electronic detectors, a million times harder for photographic plates. In that difficult transition period of the early 1990s, astronomers often worked with scanned photographic plates, in the same way that film photographers today scan their negatives to share them on the internet. But the characteristics of film photography that some people cherish so much today are deadly for scientists. That gentle roll-off you see in the highlights of a film image? That means that if you want to use bright sources to calibrate your images, you can’t directly apply them to faint sources — which is what most of the objects you are interested in are. That lovely grain that is the soul of a photographic image? An annoying source of noise that limits severely how faint we can see.
Like every medium, astronomers were conditioned by photographic plates into expecting a certain kind of reality. When they first imaged massive galaxy clusters with electronic CCD cameras, they were astonished to see many elongated arc-like structures. These were actually images of distant background galaxies which had been magnified by their light passing through concentrations of dark matter inside the cluster. By measuring these distortions, astronomers could compute how much dark matter was inside the clusters. An astonishing result. But those clusters had already been imaged by photographic plates, they’d already seen the arcs. Scientists thought they were simply defects in the emulsion. Nobody expected to see things like this, so they were not looking for them.
So my everyday job is to distil some essence of the Universe captured into digital images. To abstract reality down to numbers which we’ll then try to fit into a conceptual framework telling us how things really are. And we have to hope that we’ve understood every aspect of the instruments we are using to capture that data. We have to hope that there is no profound truth lurking in plain sight because we don’t recognise it or have discarded it. That’s the challenge at least in Euclid, which will try to measure things that are currently well beyond our ability to measure.
But meanwhile we are in lock-down and I am in Montsouris focussing my 70 year-old Summitar lens on that statue I’ve been taking pictures of almost every day for two months. It’s an overcast day in the middle of November. That means the shutter should be set to f4 or f5.6, exposure time of 1/60s I say to myself. A slow speed. After a few weeks of this, guessing the light seems now to be like smelling the air for rain. You have become sensitised to the natural environment. Slow shutter speeds and low depths of field, I say to myself, but that statue is not moving. I don’t have to turn my camera on because it is always on: a purely mechanical object. I don’t even need to change any settings because today the weather is the same as yesterday.
I don’t care about the grain down there on the emulsion, or capturing in colour, or that I can’t check the image afterwards. You don’t need thousands of ISO to take a picture that you are going to print on a sheet of paper no larger than 30×40 centimetres. My modest 100 ISO film was already a high-speed film when this camera was made. There are no distant galaxies on the other side of the lens and there is nothing I will want to measure in the image. In any case I see what the image will look like after I have taken it, I know how Rodinal will reveal the image frozen in the grains of silver.
My finger hovers over the shutter. I just want to capture this particular instant of light and shade in this particular corner of the park. My eye goes from the little round rangefinder window to the reassuring 50 millimetre-view of the world in the finder window. I am not bringing my eyes too close, of course: I have already scratched my glasses a little on the old metal rim of the finder. How many different ways are there to take a photograph of a statue I wonder? I think of the man who sold me my M6 five years ago, who told me specifically that day that he didn’t want to take pictures of statues. But then there was Eugene Atget, right? And later on, Friedlander too. They both found a new way to take pictures of statues. And if not, well, there are still the little dogs in the park, and they are not wearing masks. Click.