AV News 174 - November 2008
Photoshop Which File Format Should I be Using?
Keith Scott FRPS
Before using any image file format its basic attributes and limitations should
be understood thereby enabling informed choice of which to use, when,
where and why. Most of us use .jpg (as an end result) within AV sequences,
but should be editing and saving .psd files to take advantage of Photoshop’s
many facilities. AV workers should be aware of six different file formats and
their attributes. Although all six formats can be used within Photoshop three
of these should really be considered at the camera stage long before any
Photoshop involvement.
TIFF the “tagged image file format” recognised by its .tif or .tiff file
extension is popular and very useful. This format produces excellent quality
images ideal for transferring to and from different systems or equipment,
simply because it achieves its initial objective of “a tag-based file format for
storing and interchanging raster images”. The first TIFF specification was
published by Aldus Corporation in 1986 but developed in collaboration with
various software and scanner manufacturers; it has since undergone several
specification revisions. Because TIFF files receive some processing within
camera they don’t actually retain the “exact” same data as captured by the
camera sensor, and generally TIFF is the largest file type so storage space,
media card capacity, and battery power needed by cameras to write this type
of file should be considered.
Probably the most popular image file format in use today, yet not
necessarily the best for every purpose are JPEG which in reality are a sub
category of a “lossy compression standard” (ISO/IEC 10918-1:1994). Lossy
means that some visual quality is lost by the compression process. These
files have an extension of .jpg or .jpeg and originated by the Joint
Photographic Expert Group formed in 1986, subsequently issuing a digital
compression and coding standard in 1992 approved in 1994. Current
consumer digital cameras are usually set to .jpg format as factory default.
Compression capabilities (typically 10:1 but sometimes much greater)
significantly reduce file size thereby permitting many exposures to be st ܙY