|Night photography: capturing movement and light|
One of my favourite workshops is 'Shoot the City', a workshop I run twice a year for Gulf Photo Plus in Dubai. We start the day photographing architecture (normally at the DIFC in the heart of the city), after which we shoot the Jumeirah Beach skyline from the Palm: from late afternoon until about 30-40 minutes after sunset. We then head up to the rooftop bar of the Four Points Sheraton hotel on Sheik Zayed road: a great vantage point, with affordably great fries and tolerably cheap beer.
During each workshop I teach pretty much the same techniques, most of which I've listed below, but during the latest workshop I decided to try something a bit different ...
Before I go into that, here are some general guidelines you'll find useful if you haven't tried night photography before:
First, use a sturdy tripod. Once the light starts to drop you'll find that your exposures can easily run to at least 30 seconds. If you use a flimsy or cheap tripod there's a good chance that it will move or vibrate during the exposure. To minimise any movement don't extend your tripod legs any higher than necessary, and don't raise the centre column (often the least stable component of cheaper tripods), but if you're planning on doing a lot of night photography the only reliable solution is to invest in a good tripod. Believe me, there's nothing worse than shooting a great scene only to find out later that all your images are blurred.
Second, especially when you're photographing in very dark conditions, set your camera to manual focus. In very low light most autofocus systems will hunt for something to focus on, and often get it wrong. So switch to manual focus, choose an appropriate focal distance (use infinity for skylines), and then forget about it until you recompose or change the shot.
Third, use a remote release (and/or mirror lockup) to minimise any camera movement during the exposure, and if you don't have one, use the self-timer. As a side-note, if you want to shoot exposures that are longer than 30 seconds you'll definitely need to get a remote release, either a simple device that will allow you to lock the shutter open in bulb mode, or a more complex one that will allow you to programme a predetermined exposure. Most camera manufactures produce a dedicated release, but the one I'm using at the moment is the Giga T Pro II 2.4GHz Wireless Timer Remote from Hahnel. It's not the cheapest remote on the market, but it allows you to programme exposures of any length, set timing loops, a fixed number of exposures, and so on.
Fourth, use a low ISO: there's no point in introducing unnecessary noise, especially if you want to maximise the detail in your image. The following two images illustrate this point (both are 100% crops from the original). The first was shot at ISO 100, the second at ISO 3200. As you can see, the detail is quite badly compromised in the second image.
Fifth, turn on long exposure noise reduction. Long exposure noise reduction uses dark frame subtraction (a second exposure, taken while the shutter is closed) to minimise the inherent inaccuracies of your camera's sensor, e.g. dead pixels, hot pixels, and so on. This second exposure measures any discrepancies in the way in which your sensor records data, and then subtracts these inaccuracies from the initial exposure. As such it's definitely worth using, but as the dark frame exposure takes as long as the initial exposure it can be a nuisance when you're using a longer shutter speed.
Sixth, for long exposures you'll need to calculate the correct shutter speed as your camera can't set an automatic shutter speed longer than 30 seconds. I'm not going to cover this in any detail here (there's more information in my Photoshop for Night Photography tutorial), but in essence you need to increase the ISO and/or open up the shutter, note the exposure (e.g. four seconds at f/2.8 at ISO 3200), then adjust your settings accordingly. In this example that would result in a 480 second exposure at f/5.6 at ISO 100.
Seventh, use a relatively small aperture. The following two images illustrate why. The first was shot at f/4, the second at f/16.
The starburst effect is caused by the diaphragm of the lens – the mechanism that opens and closes to control the aperture – but only when you use a relatively small aperture (around f/11 or smaller). When you use a large aperture any 'point' light sources in the scene will appear as unattractive blown-out blobs, but when you use a smaller aperture you get a much more attractive starburst.
The following two images also illustrate this point. Both were shot at f/16.
Using the guidelines I mentioned above will pretty much guarantee that you'll get sharp, detailed and well-exposed images at night, irrespective of the length of the exposure.
So far though we've only talked about scenes with little or no movement – where the shutter speed clearly makes no difference – but what about when the movement is more significant? Clearly, if you're using a long exposure, the movement will blur, but the extent to which this is significant, or desirable, depends on the type of scene you're shooting.
For example, if you take a look at the following image you'll see that the crane on the building just to the right of the centre rotated during the 30 second exposure, adding some motion blur and additional interest to an otherwise stationary scene.
In the following shot the headlights from the cars travelling along the Sheik Zayed road have 'fused' into a continuous trail. Generally speaking, for fairly fast moving traffic, a shutter speed of 8 seconds or above works well. Slower than this and the trails from individual cars will be visible: as segments of light rather than a continuous and smooth trail. For traffic that's moving slower you'll find that you need a proportionally longer shutter speed in order to add the same degree of blur.
Shot from the Four Points Sheraton on Sheik Zayed road (15 second exposure)
In the previous example the movement (the headlights from the individual cars) was smoothed by using a relatively long shutter speed. In the following example the movement was partially a consequence of the 13 second exposure – the street lights rushing by – but also a consequence of hand-holding the camera during a 13 second exposure. So part motion, part camera blur.
In the next example, despite the fact that the motion appears to be quite pronounced, the shutter speed was relatively fast (0.3s). In this case the motion is entirely unnatural: the camera was rotated at a busy intersection (the light sources are traffic lights, car lights, and so on.
In the next two examples – a six minute exposure and a 30 second exposure – the movement of the water has been smoothed, hence the diffuse reflection from the light beneath the pier (in the first shot) and the various lights from the Jumeirah Beach buildings in the second.
Having taken the Jumeirah Beach skyline image during all of my Shooting the City workshops, or a variation thereof, I wanted to try something a bit different this time: I wanted to freeze the water rather than smooth it.
The shutter speed for the metered exposure at f/8.0 and ISO 100 was 30 seconds. To freeze the water I worked out that I needed a 1/4 second exposure, which was a bit slower than I'd guessed, but even so, shooting at f/8.0 would have required ISO 12800 to match the exposure of the first shot. I was shooting with the Sony SLT-A99, which is pretty good at high ISO, but nowhere near good enough to capture sufficient details in the building at such a high ISO.
As such I decided to blend two images: one shot at f/8.0, ISO 100 was 30 seconds, the other at f/4.0 (I decided to compromise on the aperture to keep the ISO a bit lower, ISO 3200 and 1/4 seconds. I've reproduced both initial images below.
At this resolution both shots look OK, though obviously need a bit more work, but if you take a closer look you'll see that the detail is compromised in the ISO 3200 version.
In the case of the buildings this level of noise isn't acceptable, and while it could be removed using a range of noise reduction plugins, it would take a lot of the fine scale detail with. In the case of the sea though things weren't quite as problematic, a) because the noise wasn't quite so pronounced, and b) because the fine scale detail was irrelevant: rippling water is supposed to look smooth.
To cut a long story short then, all I needed to do was blend both versions in Photoshop – i.e. use the ISO 100 version for the buildings and sky and the ISO 3200 version for the water (after running some fairly serious noise reduction). The net result, after some additional post-production (nine curves to make some global and selective changes to brightness and contrast) was the following image.
While this may not be my favourite image that I've taken from this location I am pleased with how it turned out, both from a creative point of view – it's different to all the other slow shutter speed shots I've taken – and in terms of the fact that it's technically OK too: I'd be happy to print it out as the only loss of detail due to the noise reduction is largely irrelevant to the quality of the image as a whole.
I'll be posting this one as next week's Mini-PSD, so if you already subscribe to our photography and post-production tutorials you'll be able to take a closer look at the various changes I made to this image during post-production.