| High-speed
Photography with Digital Still Cameras
Many people have made the switch from film to digital. Digital
cameras are great for doing high-speed photography, because you can
instantly see what you photographed. And you don't have to waste
film on all those shots that didn't capture quite the instant you
wanted. We recommend using digital SLRs for greatest creative
control. There are many available at reasonable prices. When we
first wrote this section 5 years ago or so, you had to pay about
$5000 for a good digital SLR. We put good in italics, because
what was good 5 years ago is low end today. Nowadays, you can get
much-improved cameras for $500.
We provide information in this section on:
Features to look for in a digital camera include:
- Manual focus control: Room lights are usually
turned out before taking a high-speed flash photograph. In a
dark room, a camera in autofocus mode will hunt continuously for
something on which to focus. With manual control, the camera can
be focused before the lights are turned out.
- Manual aperture control: For high-speed flash
photography, the flash unit is used off camera. This requires
that the camera aperture be set manually for the expected flash
exposure on the subject.
- Manual shutter control: The shutter is held open in a
dark room in readiness for the flash discharge. This usually
requires a bulb setting, or, alternatively ...
- Shutter durations of at least 1 second: For most
high-speed photographic situations, it's possible to initiate
the high-speed event in a time period of about a second. For
example, for a balloon burst, the shutter button can be
depressed and the balloon popped before the shutter closes a
second later. This works because human reaction time is
typically under a second. Shorter shutter durations can be used
successfully, but 1 second provides a margin for error.
- Ability to disable the built-in flash: Many
digital cameras have built-in flash units. It must be possible
to disable this flash. The high-speed event is captured with an
external flash.
- Override control: Some digital cameras won't allow you
to take a picture if the subject is too dark and you're not
using the built-in flash. The camera should provide a way to
override this annoying feature. If not, there is a way to get
around it. A pen light can be shined into the camera's photocell
as the shutter is opened.
- AC power adapter or rechargeable batteries: Some digital
cameras go through batteries quickly. An AC power adapter is a
convenient accessory. While having a power cord connected to
your camera is inconvenient for candid photography, it's no
problem when the camera is mounted on a tripod for high-speed
photography. Rechargeable batteries are good if they don't have
to be recharged often. The rechargeable lithium batteries that
Sony cameras use hold a charge for a long time. Rechargeable AA NiMH batteries used in many digital cameras need more frequent
recharging.
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The advantage of immediate playback of
recorded images is one that makes the digital camera attractive for
capturing momentary events. With immediate playback, one doesn't have to
develop and print film before deciding on how to improve a
photographic setup. With these cameras, it's also possible to output
images to a video display.
A disadvantage of digital cameras used to be that the image resolution
didn't match that of conventional film. However, resolution isn't
really an issue anymore unless you're using an older digital camera.
One problem that the chips in digital cameras
have is that they generate random electrical signals that degrade image quality at
long exposure times. This problem may become particularly noticeable
for exposures of several seconds. However, chips are improving, and
noise is becoming less and less of a problem. Some cameras have
built-in processes for minimizing noise. If, however, you're using
an older camera that has noise problems, keep the exposures less
than a second. If you need to remove thermal noise from an
image, it can be removed in the image-editing process without
significant degradation of the important information in the image.
Examples are provided on the next page.
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