Photographing The Sky
Always carry a camera if you are interested in clouds. Some features are seen so rarely that a photograph with even the simplest camera may be of interest. Similarly, some effects such as Kelvin-Helmholtz waves are not only rare, but extremely short-lived (lasting for perhaps a few tens of seconds rather than minutes). Modern digital cameras are everywhere, but even ‘old-fashioned’ film cameras still have a place – and are even preferred by some professional photographers.
These notes are primarily aimed at users of compact digital cameras, but naturally anyone with a digital single-lens reflex (DSLR) camera will have similar settings that normally cover a much greater range. Even the cameras on some mobile phones have a surprising range of controls, so do make sure that you can (and do) refer to the manual, often sadly neglected by users who ‘want to get on with taking photos’. Most digital cameras come with a CD containing the manual in the form of a pdf (portable document file). Copy that to your computer (and the reader, if necessary), so that you can refer to it easily without the CD. If there was no CD, you may be able to download a full manual from the manufacturer’s website. The same applies to the more sophisticated mobile phones.
Don’t be afraid to experiment. With digital cameras it is easy to try different settings, and then discard any images that you do not like. Be wary, however, of using any image-processing software that came with the camera to alter the colour balance of images, because it is so easy to produce unnatural pictures – and that is not what Cloud Appreciation is all about! (Generally, however, slight adjustments to brightness or contrast may be perfectly acceptable.)
Most compact cameras (in particular) offer a range of settings for different types of scenes. These are basically exposure settings, chosen to make the best of particular types of subject. The most useful for clouds are: landscape, snow/beach, and sunrise/sunset. The landscape setting is usually fairly satisfactory, but if the clouds are brilliantly white, the snow/beach setting may give better results, because of the way it adjusts exposure (discussed shortly). The sunrise/sunset setting usually gives a better rendering of the orange and red colours seen at those times of day. Make sure that the flash is turned off – on some cameras it turns on automatically when you change a setting – because although it makes no difference to clouds or skies, it can affect the exposure that the camera ‘guesses’ to be correct. Clouds and skyscapes generally show little movement, but just occasionally, if you are including a stormy sea, for example, a ‘sport’ setting may help.
Although DSLR cameras have interchangeable lenses, most compact cameras have a zoom facility. If this is an optical zoom, you can make free use of this to frame your subject closely. Don’t forget that a ‘close-up’ of a portion of a cloud may make a more effective picture than a wide-angle shot. If, however, your camera has a digital zoom facility, don’t be tempted to use it. It merely enlarges a small area of image falling on the sensor and, in so doing, loses resolution and definition. If you don’t have an optical zoom and feel you need to magnify part of the image, it is usually better to do this later, when you have transferred the image to your computer. A similar consideration applies to the ‘panoramic’ function available on some cameras, especially the Advanced Picture System (APS) film cameras. The ‘panoramic’ function merely crops off the top and bottom of the image, to give an apparently long, narrow picture. The resolution remains the same. Note that this is completely different from combining several photographs taken in short succession, which may be combined in the computer to give a panoramic image. We will mention these again shortly.
The normal exposure setting on cameras assumes an average scene, with a brightness that corresponds to a mid-grey tone. This is why clouds such as cumulus or cumulonimbus illumnated by sunlight, or snow scenes fail to reproduce as brilliantly white, especially if they fill most of the frame. Increasing exposure (or switching to snow/beach setting) should improve things. In addition, most compact cameras allow for exposure compensation, to make the overall image darker or lighter. This may be indicated by a control marked: +/- (or something similar). Experiment with this, to lighten the brightest areas, but try not to lose detail by making the image too bright. Some compact cameras, and a few of the most sophisticated mobile phones allow you to choose which part of a view should be used for setting exposure. But even here, remember that the camera will assume that the area chosen should appear as a grey, middle tone, so increased exposure will still be necessary.
A polarizer is the single most useful accessory for photographing clouds. By rotating the filter, you can lighten or darken clouds or the sky or reveal details otherwise difficult to see. The strength of the effect depends on the exact circumstances at the time and the location of clouds relative to the Sun. Polarizers have most effect at 90° to the Sun – so don’t expect them to make much difference when the Sun is behind you – and they will not help if clouds are silhouetted against the Sun.
Circular polarizers are best, because the linear type may affect the way in which exposures are determined. See if you can obtain one to fit your camera. A screw-on filter mount is best, but even if your camera does not accept screw-on filters, not all is lost! Buy a filter that is slightly larger than the clear aperture of your lens, hold it up in front of your eye and turn it until you get the effect you want. Then, keeping the same orientation of the filter, hold it in front of the lens while you make the exposure. (With light-weight compact cameras this is usually possible to do, but mounting the camera on a tripod will make it easier.) Although polarizing filters do absorb a small amount of light, the camera’s exposure system will normally compensate for this without any problems.
The two photographs shown here demonstrate the great difference that a polarizing filter can make. The first phototograph was taken with the filter rotated to bring out the distant, white clouds, and the filter was rotated by exactly 90° degrees before the second photograph was obtained.
Here, the polarizing filter is set at an angle to bring out the distant white clouds.
Here it is turned a further 90 degrees.
True panoramic images of clouds, consisting of two or more images that are combined in the computer, may be extremely effective, provided there is little rapid motion of the clouds. It is important to have an adequate overlap between the individual images. Some compact cameras offer assistance in creating these, primarily by showing guide lines to help with framing the separate shots. When hand-holding the camera, with care, it is often possible to take a couple of images that may be combined later, but generally it is best to use a tripod for stability and for ease in framing, especially if several images are to be combined. The more images are used, however, the more complications arise, primarily in the matter of exposure. Unless you are able to lock the exposure, or are experienced in adjusting exposure later in the computer – and even then it may require a lot of work – it is probably best to restrict yourself to just two or three images. The first image shown here is a preliminary version, consisting of two separate frames. The join is just visible, but was removed with later adjustment.
This image is a combination of two smaller images. The join is visible.
The second image (again a preliminary version) consists of six separate frames. The problems in exposure at the right-hand end of this panorama were actually caused by slight changes in the lighting, which was affected by clouds behind the photographer coming between the Sun and the cumulonimbus cloud.
This Cumulonimbus panorama was created from six original images. With more adjustment, the joins will become invisible.
Amongst Storm Dunlop’s many publications, ‘Photographing Weather’, Collins Gem Weather and ‘Sky’ are particularly relevant to budding cloud photographers.
(All photographs © Storm Dunlop)
