TIFF is the
format of choice for archiving important images. TIFF is THE leading commercial
and professional image standard. TIFF is the most universal and most widely
supported format across all platforms, Mac, Windows, Unix. Data up to 48 bits
is supported.
TIFF supports
most color spaces, RGB, CMYK, YCbCr, etc. TIFF is a flexible format with many
options. The data contains tags to declare what type of data follows. New types
are easy to invent, and this versatility can cause incompatibly, but about any
program anywhere will handle the standard TIFF types that we might encounter.
TIFF can store data with bytes in either PC or Mac order (Intel or Motorola CPU
chips differ in this way). This choice improves efficiency (speed), but all
major programs today can read TIFF either way, and TIFF files can be exchanged
without problem.
Several
compression formats are used with TIF. TIF with G3 compression is the universal
standard for fax and multi-page line art documents.
TIFF image files
optionally use LZW lossless compression. Lossless means there is no quality
loss due to compression. Lossless guarantees that you can always read back
exactly what you thought you saved, bit-for-bit identical, without data corruption.
This is a critical factor for archiving master copies of important images. Most
image compression formats are lossless, with JPG and Kodak PhotoCD PCD files
being the main exceptions.
Compression
works by recognizing repeated identical strings in the data, and replacing the
many instances with one instance, in a way that allows unambiguous decoding
without loss. This is fairly intensive work, and any compression method makes
files slower to save or open.
LZW is most
effective when compressing solid indexed colors (graphics), and is less
effective for 24 bit continuous photo images. Featureless areas compress better
than detailed areas. LZW is more effective for grayscale images than color. It
is often hardly effective at all for 48 bit images (VueScan 48 bit TIF LZW is
an exception to this, using an efficient data type that not all others use ).
LZW is
Lempel-Ziv-Welch, named for Israeli researchers Abraham Lempel and Jacob Zif
who published IEEE papers in 1977 and 1978 (now called LZ77 and LZ78) which
were the basis for most later work in compression. Terry Welch built on this,
and published and patented a compression technique that is called LZW now. This
is the 1984 Unisys patent (now Sperry) involved in TIF LZW and GIF (and V.42bis
for modems). There was much controversy about a royalty for LZW for GIF, but
royalty was always paid for LZW for TIF files and for v.42bis modems.
International patents recently expired in mid-2004.
Image programs
of any stature will provide LZW, but simple or free programs often do not pay
LZW patent royalty to provide LZW, and then its absence can cause an
incompatibility for compressed files.
It is not
necessary to say much about TIF. It works, it's important, it's great, it's
practical, it's the standard universal format for high quality images, it
simply does the best job the best way. Give TIF very major consideration, both
for photos and documents, especially for archiving anything where quality is
important.
But TIF files
for photo images are generally pretty large. Uncompressed TIFF files are about
the same size in bytes as the image size in memory. Regardless of the novice
view, this size is a plus, not a disadvantage. Large means lots of detail, and
it's a good thing. 24 bit RGB image data is 3 bytes per pixel. That is simply
how large the image data is, and TIF LZW stores it with recoverable full
quality in a lossless format (and again, that's a good thing). $200 today buys
BOTH a 320 GB 7200 RPM disk and 512 MB of memory so it is quite easy to plan
for and deal with the size.
There are
situations for less serious purposes when the full quality may not always be
important or necessary. JPEG files are much smaller, and are suitable for
non-archival purposes, like photos for read-only email and web page use, when
small file size may be more important than maximum quality. JPG has its
important uses, but be aware of the large price in quality that you must pay
for the small size of JPG, it is not without cost.
Explain the TIFF image format in detail.
Reviewed by enakta13
on
March 16, 2013
Rating: