Victoria Falls – hand-held from a helicopter taken at 1/1600 sec to avoid vibration caused by the aircraft
Shooting from Vehicles
It’s not always humans that cause camera shake. Vibration from cars, boats and aircraft can ruin images. There’s a combination here of the movement of the vehicle as it travels and the engine itself causing a different frequency of vibration. The only way to get past this is trial and error, erring on the side of as fast a shutter speed as possible. I took a series of images of Victoria Falls from a helicopter and needed at least 1/1600 sec to avoid the aircraft’s motion softening the image. Image stabilisation can help of course, although I didn’t have it on the lens I was using in the helicopter. You can cut out some of the motion, by stopping the car or boat’s motor as you shoot. Although I wouldn’t recommend doing this with a helicopter!
Aperture and lens choice
Some lenses are inherently sharper than others. Prime lenses are usually better than zooms and professional lenses are sharper than consumer models. It’s also worth knowing that each lens has an optimum range of apertures where it achieves best resolution of the image, and therefore the sharpest shots. Lens characteristics vary considerably from lens to lens and there are reference sources where you can look up your own lenses.
In general though, the advice is to shoot with the lens stopped down two or three stops of aperture from the maximum aperture of the lens for optimum sharpness.
So, if you have a lens with a maximum aperture of f/4, the sharpest shots are likely to be had at around f/8 to f/11. With the exception of very expensive optics, most lenses are a bit soft at wide open aperture. That’s a shame because background blur (bokeh) is a lovely thing with a wide open lens.
Lens construction, materials and coatings are getting better all the time, but you should still be aware that always shooting wide open may not result in the best images. This is something of a kick in the teeth for anyone who needs to shoot in low light! In order to achieve the fastest shutter speed, it’s necessary to open the lens up to it widest aperture to let as much light in as possible. Such is life and this is one of the many compromises in photography.
My advice about lenses is pay as much as you can for the best you can afford. Unless you’ve been conned, an expensive lens will resolve light into sharper detail on the sensor at a wider range of apertures than a cheaper model.
An Aperture too far
Don’t assume that closing down a lens’s aperture to its minimum value (say, f/22 for example) will result in the sharpest images. Another factor comes into play when the hole that the light passes through gets tiny: diffraction. Diffraction is where the rays of light separate out as they emerge from a small aperture and end up arriving at the sensor at slightly different times as they fan out – the outer rays have further to travel. This spreads the light across more sensels (sensor pixels) than necessary and the individual light rays interfere with each other to create light and dark areas, effectively smudging the image.
I should also point out that if you shoot everything at f/22, not only will all your images have distracting backgrounds due to the large depth of field, but this small aperture won’t let much light in at all. In turn, you’ll need a slower shutter speed or higher ISO value (or both) to expose the picture properly, potentially introducing camera shake and image noise respectively.
Remember that a lens has a range of optimum apertures somewhere in the middle of its maximum and minimum apertures. This is usually between a couple of stops from maximum aperture and a couple from minimum.
You may already know that using a high ISO setting on your camera can introduce unwanted noise into the resulting image. It’s another photographic irony that increasing ISO in order to obtain faster shutter speeds and a corresponding reduction in camera shake can soften the image due to the amount of noise present. You’ll have to experiment with what you find acceptable for your camera, but you’ll find that after a certain value of ISO, the camera will record less detail and dynamic range and your pictures will need more noise reduction in post-production. And, you guessed it, noise reduction reduces sharpness.
If you’re concerned about noise in low light conditions, why not use a bit of flash? This will instantly alleviate the problem of noise and can also give you an effective shutter speed far greater than that indicated on the camera. How so? Well, in dark conditions, you set the camera’s exposure to deliberately underexpose whilst making the flash do all the work. In these conditions the flash’s duration is much shorter than the camera’s shutter is open and you’ll be able to freeze the motion of your subject at anything up to 1/38500 sec. I go into more detail on flash techniques in this post on photographing swallows.