Mourne Sunset

Yesterday, the mystery was the wind. Today, it may well be teaspoons.

That AA Milne poem came back to me as I photographed a landscape of the Mourne Mountains in the light of last night’s setting sun. I knew I wouldn’t get a sharp image of anything because the air was moving as thermals, returning the day-borrowed heat into the atmosphere. Locally becalmed in our isolation, yes, but the Mournes are 100 km distant. All of that radiating heat becomes a cooling and distorting visible haze over that distance of an evening.

The mist at the foot of the range was thickening as quickly as the light was fading. There was no time to waste. I grabbed the DSLR and swapped lenses at the kitchen table explaining to Lia that I’d be gone ten minutes before we could watch the Turin murder-squad dealing badly with moral dilemmas in Thou Shalt Not Kill. I tell you this to illustrate how photography often relies on serendipity and opportunism, not in criticism of the Italian police.

Once at the top of the house, the lens aimed out through an open window like an assassin’s bazooka, I could have tried to minimise the blur by using a tripod. Or a really fast exposure. I did neither. I simply braced myself against the window frame and set the shutter to remain open for 2.5 milliseconds. I tested the exposure with a photo of Slieve Gullion at 600 mm (below) but the more interesting scene was The Mournes. I decided on a 400 mm focal length and a Tv of 1/400 s. ‘It’s going to need a panorama of three’ I thought. So now I needed to commit to a manual exposure so that all three photos had identical exposures lest the overlapping seams be ugly. I’d need a big aperture to gather a lot of light but what about the depth of field? Choose f/6.3 and let the ISO be 1000. Done. So be it.

You know, because I just told you, the Mourne Mountains are about 100 km from my camera. You probably have no reason to care that a lens with a 400 mm focal length has an angle of view of some 5°, more or less. What that means is that the field of view at 100 km is about 10 km, give or take. I took three photos and stitched them together in Lightroom, overlapping them by 50%, approximately. Finally, I can tell you the landscape above depicts some 20 km of the Mourne Mountains as seen from the south.

I think that’s pretty amazing from photography done in ten minutes or less. And I developed the image to dimensions of 4 by 18. That’s no coincidence because it’s the shape of my scarves, 40 X 180 cm. And this image became my 303rd scarf design, 150 Mbytes with an average colour often called sandrift, a hue of brown. And to think I’ve only offered ten scarf designs for sale, so far.

I awoke this morning thinking about William Blake. ‘Hold Infinity in the palm of your hand’. As a printer, he must have known he was printing ‘eternity in an hour’. And there’s more on Blake coming soon.

With infinity and eternity in mind, the volume of air in that photograph suddenly interested me. I’d never really thought about it before. How much air am I capturing in my photographs? I think that’s an easy calculation based on pyramid mensuration if we agree that the camera is at the apex and the image is the base of our pyramid.

First, let’s estimate the area of the base of the pyramid. I told you a scene at 100 km distance is about 10 km wide. So let’s now say the image height is about five times as high as the highest peak we see which is Slieve Donard (850 m), and agree that half is submerged below the foreground, so to speak. And recall that I merged three pictures with 50% overlap, so we have an image that’s 20 km wide and I’m saying it’s rounded up to 2.5 km high above sea level. So let’s say the image area above the sea is 50 km².

Second, take my word, the Mournes are 100 km away to the north in another country likely to be self-isolating outside the borders of the EU for years.

And third, as you recall from measuring cone-head volumes in school, we’ll estimate the volume of the pyramid as the base times the distance to the mountains, and then you divide by a triangular factor of three. Keeping the number friendly, that’s some 1700 km³ of air moving between me and The Mournes.

And you probably don’t need me to tell you that the-not-quite-so empty spaces in the Mourne May Sunset photo at the top of this journal weigh a brain-freezing amount. What? You don’t believe me?

You know how trees are displaced by wind? And you know air has mass otherwise the insects and pterodactyls would never have developed wings.

You may not realise there’s some 1000 kg of air resting on your shoulders as you read this. Anyway, let’s dispense with the engineering complications of pressure variations and humidity estimates and temperature fluctuations and use a ‘standardised’ weight of air. Which is more or less 1.3 kg/m³. And lo and behold, there’s an online calculator to calculate the weight of volume of things. But you don’t need that to multiply 1700 km³ × 1.3 × 10⁹ by to get some 2 trillion tonnes of air.

Mind you, the online calculator offers the answer in metric teaspoons (3.4 × 10²⁰ since you insist) which might be a useful relative measure for any chefs that happen to be reading to this article.

So there it is. You really didn’t need me to tell you that the-not-quite-so empty spaces in the picture at the top of this journal weigh a brain-freezing amount. So I’ll let you work out the equivalent in the Slieve Gullion Sunset photo. Or not.