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The RAW is the only file format that
allows to fulfill the potential of the
camera; it is a kind of "digital negative",
since is provides an unprocessed image that
must be optimized with an image editor
before being printed or published on
internet.
RAW is not a single file format. Every
manufacturer uses a proprietary RAW format:
for example, the Canon's RAW is .cr2 ; Nikon's RAW is .nef ;
Olympus's RAW is .orf , etc. Other than
that, every camera has a slightly different
RAW format, so if you buy a recent camera
you may not be able to open its RAW files
until the raw converter of your post
processing program has been updated to
support the file format of the new camera.
RAW files are almost
unprocessed; you can change many image
parameters (contrast, sharpening, colors
space, white balance) when you open
the file with your raw converter. This is one
of the great advantages of RAW: for example,
if you accidentally apply an exaggerate
in-camera sharpening to the RAW file, you
can correct it. With JPEG, instead, there is
not way to correct in-camera oversharpening
and other errors.
Another advantage
of RAW
is the bit depth: RAW files are 12 or 14 bit,
while JPEG is 8 bit. The bit
depth is an important attribute of every
image format; it specifies how many bits are
used to create a color, and then how many
shades of color can be represented. The
bits are the basic units of the entire
digital world. A computer understands just
two values : 0 (off) and 1 (on); and a bit
is right that : a 0 or an 1. To get more
values, you have to combine more than one
bit. With two bits, you have four (2²)
values : [0,0]; [0,1]; [1,0]; [1,1]. Three
bits correspond to 2³ -> 8 values, 4 bits->
16 values, etc. A commonly used bit depth is
8 bit, that has 256 values per channel.
Other bit depth used in cameras and scanners
are 12 bit (4096 values) and 16 bit (65536).
These values are referred to just one color
channel: if you consider all three channels
(red, green, blue), you have 16,8 millions
of tonalities with a 8 bit image, while a 16
bit image has 281474,9 billions of
tonalities! The obvious advantage of high
bit depth is that you you can represent much
more subtle color tonalities and you can
make heavier adjustments during the post
processing; other than that, you need a wide
bit depth to store the entire dynamic range
that the camera is able to capture.
These crops show the advantage of RAW vs
JPEG.
The image A is a crop taken
from a very dark shadow area of a photo. The image B is the same
crop, taken from a JPEG image and brightened
up with levels to show some detail. The image C is the crop
taken from a RAW image (14 bit) and
brightened up by about 4 stops. The colors
and the detail in the RAW photo are much
better, the image is sharper and it has more
natural colors.
Let's see an example in
opposite situation: a very overexposed area.
When you have to recover
highlights, the difference between RAW and
JPEG is huge. Image A is a crop from the
original photo, overexposed by about 3
stops. B is the image recovered from JPEG,
while C is recovered from RAW: the raw
version is much much better, it has
recovered a lot more detail and it has a
more pleasing look.
If you do nature photography, you should
always use RAW as in-camera file format.
JPEG is a great format for internet, but it
does not give the same quality of RAW. Sport
photographers or photo journalist can trade
some image quality for the faster workflow
given by JPEG files, but for nature
photographers there is not any reason to
shoot in JPEG: the only "advantage" of JPEG
is the smaller file size, but nowadays
memory cards are cheap and they offer huge
capacities.
In the latest years, some cameras have added
a "sRAW" mode, that is a RAW file at reduced
resolution. I recommend to avoid this
useless file format: you don't get any
advantage and you just lose resolution. The
noise is the same that you get by shooting
in full RAW and downsizing with Photoshop,
and, even though the file size gets a bit
smaller, it is not a big advantage because
with today's memory cards storage space is
no longer a problem.
Do you have
comments or questions?
If you have comments or questions about
this article, feel free to ask in the
Juza
Nature Photography Discussion Forum!
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