Deciphering digital camera jargon By Jay Dougherty


dpa German Press Agency
Published: Friday January 12, 2007

By Jay Dougherty,
Washington- Digital cameras stem from computers as much as
they do from the optical heritage of film cameras.
It's no wonder, then, that today's digital camera users are
bombarded with a plethora of acronyms, just as computer users have
been for years.

Buy a digital camera, and you'll be confronted with terms such as

RAW, ISO, and noise. What does all of this mean? Read on for some
answers.

Q: What's a RAW file?

A: Many digital cameras take images in one of two formats: JPG and
RAW. Some cameras even offer the option of recording images in both
format simultaneously.

A RAW file records image data directly from the camera's main
imaging chip, with little or no internal processing in areas such as
contrast, saturation, and sharpness. JPEG files, on the other hand,
are the result of a digital camera's internal interpretation of the
data it receives from the camera's imaging chip, often called a
"sensor." JPEG files are also compressed, meaning they have digitally
thrown away some of the data that came from the camera's imager, and
as a result they're almost always smaller than RAW files.

Just about any graphics viewer or editor can work with JPEG files.
RAW files, on the other hand, often require the software that came
with your camera. Many enthusiasts and pros prefer RAW files because
they want to be the ones who enhance the file in software.

Q: What is ISO?

A: ISO is a term that the digital camera makers borrowed from the
film industry to describe how sensitive a camera's sensor is to
light. Short for Internatianal Standards Organisation, ISO levels on
today's digital cameras typically range from values of 100 to 1600,
with the lower numbers representing less light sensitivity.

When your camera's sensor is more sensitive to light, it can be
used in lower light situations, such as indoors. Brightly lit
situations require less sensitivity to light, so lower ISO settings
can be used.

Your camera's internal metreing system, which ensures properly
exposed images, works in conjunction with the ISO setting of your
camera to control how long the camera's shutter must remain open to
obtain a well lit image. If your ISO setting is too low for the light
level available, your camera's metre will force the shutter to remain
open longer to let more light in, and you'll have to hold the camera
very steady - or have it on a tripod - in order to get a shake-free
image.

For outdoor photography, ISO settings of 100 - 400 are
appropriate. For indoor photography, settings of 400 - 1600 are
preferred.

Generally you want to use the lowest ISO setting possible in a
given light situation in order to avoid digital noise.

Q: What is digital noise?

A: When a digital camera has to boost its sensitivity to light in
order to record an image properly, digital noise occurs. Digital
noise manifests itself through tiny red and blue dots in an image -
often more perceptible in large areas of uniform colour, such as the
sky or ocean.

Analogous to digital noise would be the hiss you hear in audio
sources when you need to turn up the sound in order to hear a weak
signal. Digital noise can also be akin to film grain in photographic
prints from film cameras.

At lower ISO settings, generally in the range of 100 - 200,
digital noise is almost nonexistent. As you increase the ISO of your
digital camera, digital noise becomes more apparent. Noise will be so
apparent at ISO settings above 800 that some camera users feel
pictures taken at these higher ISO levels are unusable.

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