SHOOT RAW! Sponsored By HITACHI Microdrive Digital Media
Written by Shane Schmidt, Technical
Marketing Manager,
Pexagon Technology, Inc.
Introduction:
Digital camera technology has improved with leaps and
bounds over the past several years. The digital cameras of today allow
us to capture an increasing number of high quality images by way of large
capacity storage cards, larger imaging chips and outright faster cameras.
With each generation new features are added and existing features refined.
It’s these improvements that have spawned a new breed of digital
camera bringing 8 megapixel advanced compacts and 6 megapixel digital
single lens reflex (DSLR) cameras to the masses. A paradigm shift exists
in the number of pictures we take and the image formats we shoot.
Improvements in on-board buffers, battery life, and faster,
more accurate auto focus systems deliver benefits to digital shooters
across the board. Performance enhancements have brought digital to a new
height for the professional and the novice alike.
Larger on-board buffers
enable continuous burst depths of over 20 RAW and 40 JPEG images at rates
of up to 8 frames per second (fps). The Canon EOS 1D Mark II supports
a burst depth of up to 20 RAW images at 8 fps, the Nikon D2H up to 25
RAW images at 8 fps and the Nikon D70 up to 144 JPEG compressed images
at 3 fps. It’s speed like this that empowers the digital photographer
to capture more high quality pictures in a shorter amount of time.
Capturing
a Digital Image:
Capturing a digital
image is a process of exposing the light sensitive image sensor (CCD or
CMOS) to light. There are many things that happen in a digital camera
before the file is written to the camera’s storage card. The output
file type and size depend directly on any in-camera processing and compression
applied to the file.
The exposure, which
is the amount of light that reaches the sensor, is directly controlled
by the camera’s aperture and shutter. The aperture controls the
amount of light let into the camera. Think of this as a lens pupil. The
camera’s shutter covers the image sensor and controls the length
of time that light is able to reach the actual sensor.
Once the light reaches
the camera’s imaging sensor, the sensor records the amount of light
that hits each pixel as a voltage level. This voltage level is then converted
from an analog voltage to a digital value by the camera’s analog
to digital circuitry. Either 12 or 14 bits of data are recorded for each
pixel depending on the camera. This is what is considered the unprocessed
or RAW image data.
What happens to the
photograph after it is captured is a function of the user-specified settings.
In most cases digital cameras provide several different file formats for
output including various qualities of JPEG, uncompressed TIFF and RAW.
The output file type determines if the image is altered by the in-camera
processing and if compression is applied to the image to reduce its size.
RAW Files Explained:
RAW files are raw
image data captured by the image sensor before any in-camera processing
has been applied. The cameras settings (i.e. color correction, white balance,
sharpening, contrast, saturation, etc.) are disregarded, but are instead
written in a header file. RAW files can be compared to exposed undeveloped
film negatives in this respect.
Generally, RAW files
are not compressed and are written to the camera’s storage card
in this RAW format as 12 or 14 bit per channel files, depending on the
camera. However, some camera manufacturers may use lossless or slightly
lossy compression to reduce file size. Lossless compression is where the
image is compressed, but no information is lost. Lossy compression is
where the image is compressed and a certain amount of information is lost.
There are also situations where minimal in-camera processing may be applied
to the RAW image. The details are unknown outside of the specific camera
manufacturers.
RAW files are valued
for their latitude. Capturing the RAW image data and writing this information
in an unaltered or mildly altered state provides the photographer with
endless possibilities and potential. In most cases, post processing is
required to create a finished image, but this post processing can be done
on a computer system with more processing power and more advanced algorithms
than that of the camera alone.
The Benefits of Shooting RAW:
Shooting RAW provides benefits over other formats for many different reasons. Depending on the
situation, the benefits may be substantial or nominal. In many instances,
hi-resolution JPEG files may be adequate for the task at hand, but it’s
the latitude and potential for higher quality that makes RAW most appealing
for pros and novices alike.
Latitude:
One of the greatest RAW benefits is latitude. RAW files allow the photographer to harness
the full potential of each shot. Images are either unaltered, or minimally
altered by the in-camera process and can then be processed externally
using a computer and conversion software to achieve best results. The
photographer ultimately has control over the image and can tailor settings
to extract the best possible quality. This is most important in situations
of difficult lighting. Color temperature and white balance can be adjusted
as needed without quality degradation.
Externally processing images on a computer system allows the photographer
to choose what he/she feels to be the best tool for the job. The original
RAW file can be archived and revisited at a later date should a better
utility become available. Fast computer processors and specialized software
such as Phase One’s Capture One and Adobe’s Camera RAW plug-in
for Photoshop make post processing RAW image files fast and easy. In most
cases a conversion and processing software is provided with the camera
or can be obtained from the manufacturer.
RAW files can be easily
converted to any of the conversion software’s supported output formats
including JPEG and TIFF. Conversion settings can be customized for specific
print sizes. Maximum quality can be attained from each image. Using RAW
files as a sort of exposed, undeveloped digital film negative gives the
photographer the freedom to create and the ability to improve.
Quality:
RAW files do not suffer
from the same limitations other image file formats do. Because you are
dealing with unaltered or minimally altered RAW image data, there is greater
flexibility in applying corrections and adjustments without significant
degradation in the output file’s quality. Files can be easily adjusted
and converted from their RAW format to other file formats using either
the RAW conversion software provided with your camera or with third party
converters such as those from Adobe and Phase One. Quality is retained
and the output customized for the specific applications when needed.
RAW files support
either 12 or 14-bit per channel color bit-depth, depending on the camera.
For example, a 12-bit RAW file supports up to 4096 (2^12) discreet levels
of information or tones per channel and a 14-bit RAW file over 16,000
(2^14) levels per channel. An 8-bit JPEG file would support only 256 (2^8)
discreet levels or tones per channel. The benefit here is a higher bit-depth,
which translates into more color information in each of the three channels
(red, green and blue). Raw files can also be converted and edited in 16-bit
mode via software. This 16-bit mode allows for over 65,000 discreet levels
of information per channel. What does this all mean you ask? Well, look
at it this way. JPEG files support 256 possible color values per channel,
a 12-bit RAW file over 4,000 and a 16-bit file over 16,000. The point
being more information translates into better image quality.
When post processing
the image, the added color information of the RAW file allows for expansion
of specific parts of the color spectrum for correcting of less than perfect
exposures. This can be quite helpful when trying to alter brightness levels
or bringing out detail in shadows. The added color information of RAW
files helps to avoid posterization or banding, such as found in 8-bit
JPEG files. This banding occurs when there aren’t enough tonal values
to display continuous tonality. Where you should see a smooth gradient,
a rough jump in color or a band may appear. Evidence of the lack of tonality
can be seen in the image’s histogram.
JPEG files are pre-processing
compressed image files. The camera’s settings for color correction,
white balance, sharpening, contrast, saturation, etc. are applied to the
image and the image is compressed to reduce overall file size. The result
is a finished, processed image file written to the camera’s storage
card.
JPEG files generally
do not require post processing and are much smaller in size when compared
to RAW files from the same camera. JPEG files do suffer from quality loss
due to the compression used. Depending on the level of compression used,
the affects of the compression may or may not be noticeable. JPEG files
are considered a finished product the moment the image is captured. You
are for the most part locked into the settings you chose before you captured
the image. Post processing is possible, but is hindered by the settings
applied to the image in-camera. The cameras settings may have created
an image suitable for a specific print size, but attempting to enlarge
a print may result in less than desirable effects. JPEG files are already
fully-cooked and too much manipulation can severally degrade the output
quality.
RAW + JPEG Mode:
RAW+JPEG is a mode
most commonly found in DSLRs and advanced compacts. This is a sort of
best of both worlds solution designed to meet the need on both ends. This
mode combines the latitude and quality of the RAW file with the pre-processed,
small file size of the JPEG image format. Both image formats are captured
and written to the media. For those who need the convenience of JPEG files,
but want the latitude of shooting RAW, archive the RAW file and use the
JPEG file for the task at hand.
Now photographers
don’t have to choose which format to shoot as they can have their
cake and eat it too. In many of the models which support this feature
you are also able to choose the quality of the JPEG file produced. This
option will consume more space than JPEG or RAW alone, so the only decision
left now is how much storage to carry with you. Pack a Hitachi Microdrive
and SHOOT RAW!
Digital camera technology has improved with leaps and
bounds over the past several years. The digital cameras of today allow
us to capture an increasing number of high quality images by way of large
capacity storage cards, larger imaging chips and outright faster cameras.
With each generation new features are added and existing features refined.
It’s these improvements that have spawned a new breed of digital
camera bringing 8 megapixel advanced compacts and 6 megapixel digital
single lens reflex (DSLR) cameras to the masses. A paradigm shift exists
in the number of pictures we take and the image formats we shoot.
