Jonathan's blog

I recently moved from a flat in Kingswood to a house in Fishponds, on the very outskirts of Bristol. It overlooks the massive Oldbury Court Estate, which shortly gives way to the countryside. Compared with Kingswood, there is hardly any visible light pollution here – at least to my urban-accustomed eyes. Back in Kingswood the sky was as orange as Fanta. Here it seems a much more natural blue/black.

Since moving, I’ve been waiting for a clear night so I can point my camera at the sky and take in a wide view of billions of stars (as opposed to regular astronomy, where the photographer/observer focuses one one object). Last night presented just that opportunity, so I whipped out my 450D and fitted my 50mm f/1.8 prime lens.

I quickly found out that astronomic photography is a balancing act and a series of compromises. In short, the thing you are pointing the camera at is very dark, so you need to collect a lot of light to make a decent picture. There are three real ways of doing this (and one way of cheating).

1. Expose for longer. The trouble is, stars move across the sky. Exposing for 30 seconds, you see some blurring that just looks like poor focus. Exposing for 60 or 90 seconds, you can clearly see that the stars are all moving and have blurred tails. So in practice we have to keep the shutter speed faster than at least 30 seconds.
2. Open the aperture wider. The trouble is, the wider the aperture, the worse the sharpness. When taking photos of fine points of light, f/1.8 just doesn’t cut it (unless you have a fantastic lens). You need to stop down to at least f/8 to see the sharpness of the stars come through.
3. Increase your camera’s sensitivity (by increasing the ISO of your sensor or film). This effectively means you collect more light, so you can shorten your exposure, or decrease the size of your aperture. The trouble is, higher ISO means higher noise or grain in your picture. ISO1600 on your DSLR sounds great, until you see the results and find out it’s a load of speckle.
4. Fix it in Photoshop. This has the same fundamental effect as increasing the ISO, although you can be a bit more intelligent about noise reduction. I’m no whizz at Photoshop myself, and in any case I prefer to get it right in the camera.

So, we have to find a suitable compromise. The best combination I came up with was a 20-second exposure at f/6.3, and ISO400. Then I briefly altered the curve in GIMP to keep the noise down in the paler areas of the sky. The result was a pretty mediocre photo. The stars were a bit blurred (motion blur) and a bit blurred (poor sharpness) while the background was also a bit noisy. I somehow don’t think it will feature on the cover of New Scientist any time soon.

These are the two best photos out of about two dozen that I shot. It doesn’t sound much, but bear in mind that each one was exposed for anywhere between 30 and 90 seconds! I’m sure that converting them to JPEG and resizing down to this size has done them no favours at all, but never mind. In the first photo, the shutter speed is too long (90 seconds) and the stars are blurred, while in the second one I shot at ISO400 and played with the result in GIMP, so the noise is bad instead.

Stars flying by

The night sky

Some of these issues can be worked around. I’m using a standard Canon f/1.8 50mm prime lens. If I had some more pocket money, I could upgrade to an L-series lens (for example) that would probably offer better sharpness at wider apertures. I’m also using a decidedly consumerish EOS 450D. I am a consumer, after all, but an EOS 1Ds mkIII with a full-frame sensor would offer lower noise at higher ISOs. I’m not sure what can be done about the movement of the stars across the sky though, regardless of personal wealth. I suppose I could buy a sky-tracking tripod like they use for real observatories.

Next time It’s clear I’m going to try approaching this from a different angle. I’ll keep the ISO low at ISO100, and the aperture small at f/16 perhaps. To compensate I’ll expose for a “while” – perhaps five minutes. This should give me a low-noise, sharp photo of some extremely blurred stars. It’ll be like the world is spinning, and I hope it will look interesting. Watch this space*!

Finally, coming back to the issue of light pollution from sodium street lights – despite it seeming far better here in Fishponds, the images from the camera still seemed horrifically orange. I can get around this by either adjusting the colour balance, or by simply converting the images to black and white. I suppose I could also solve this one with money, by buying a house in the countryside

* Actually, watch my photo blog. I’ve said it before but I’ll say it again – this blog is for nerdy discussions about photography, while my photo blog is for showcasing the pictures that actually turned out OK.

You might wonder what there is to discuss about bike lights. But in my several years as an urban commuter cyclist, and with my fascination for toys such as bike lights, I’ve made some observations which might prove useful to other cyclists.

What you need

Before you go out and buy a light, decide what your needs are. Choose a bike light to suit your needs (and budget, of course). If your daily needs cover two or more of these categories, you should consider buying either a light which ticks all of the right boxes, or two lights.

How to mount your lights

When you are riding in traffic and your lights are in flashing mode, I would recommend angling your lights directly forward. Most LED lights are not bright enough to dazzle other drivers, but pointing them forwards will make them appear much brighter, and will cause them to shine into the wingmirrors of cars in front of you.

If in doubt whether your lights are too bright, or inconsiderately aimed, sit in a car and get a friend to ride your bike at you

When riding with very bright lights, it’s plain rude to point them into driver’s eyes. Dip them like every other vehicle.

When riding on an unlit path, don’t use too much light because it dazzles other cyclists. Keep your lights aimed low. Flashing lights aren’t required here to attract attention, and the flashing can make it hard for oncoming cyclists to see.

Branded vs generic

As a student, I was strapped for cash and I would always buy cheap, generic bike lights from eBay. Now I have a job, I always buy Cat Eye.

In my experience, the cheap lights are usually similar in brightness but the beam pattern is never as good as a branded light. Most importantly, the cheap lights have very poor quality brackets which usually snap off long before the light breaks. One such light whose bracket broke has now been turned into a makeshift photography light, which I gave to my brother. I’m so generous!

Nowadays I almost always buy Cat Eye. They are the Coca Cola of the bike accessories world, and I’ve always found them to be consistently high quality in terms of the brackets and the brightness, beam pattern and battery life are excellent. They’re not the cheapest, but I reckon you’ll be pleased if you buy them.

Carrying spares

I think it is crucially important to carry either multiple lights or multiple sets of batteries with you while commuting. Especially with LEDs, it’s not always obvious when the batteries are running out so it’s easy to be caught short. If your lights run from AA/AAA batteries then it’s no problem to keep a spare set in the bottom of your bag all the time.

If you’re lucky enough to own a set of lights with a rechargeable battery pack, it’s not always practical or possible to carry a spare set with you. In this case you’d be wise to keep a spare LED light with you. Doesn’t matter if it’s a cheap one

Multiple lights

As well as keep a “spare” set with you, you might want to mount two or more lights on your handlebars.

I find that having two lights on the handlebars, both flashing, is a great way to attract attention. They never quite flash in perfect time and this effect is rather eye-catching.

It also means you can put out twice as much light when running in constant mode, which is great news if your commute takes you on unlit roads or paths.

I have 5 headlights on my bike. I have a pair of RSP Asteri 2 LED headlights which I use in flashing mode in the city and dim constant mode on the Bristol-Bath bike path. I have an extremely bright pair of Cat Eye ABS-35 halogens to be used on the unlit sections of the path when there are no oncoming cyclists. They have a thumb switch to turn them off quickly if anyone comes into view. And I also have a head-mounted flasher, a Cat Eye HL-EL400.

Head-mounted lights

Head-mounted bike lights are a controversial topic among cyclists and motorists.

I use a helmet-mounted front and rear light because they can be seen over the tops of cars in heavy traffic. It used to make me nervous that if I was currently being overtaken, the car behind the overtaking car might not be able to see my rear lights mounted in the usual place, below the saddle.

I also think it’s very versatile because you can choose to direct light wherever you turn your head. Part of my journey takes me along a stretch of road that has two lanes. Drivers frequently change lanes without looking sideways, where I often am. If I have a head-mounted flashing light, I can look into the car window, directly at the driver, and then they usually notice my presence.

However, one of my colleagues who drives (and also cycles) says he dislikes head-mounted bike lights because it is impossible to see a cyclist’s eyes and therefore the driver can’t always tell if the cyclist has seen the car.