Highest Quality Capture: Workflow Phase I - Black and White in Photoshop CS4 and Photoshop Lightroom - page 30

II. Digital Capture File Formats
JPEG vs. Raw Capture
Those of you with digital SLRs or high-end point-and-shoots have a
choice when it comes to the i le format that your camera writes: JPEG
(the world and web standard for photographic imagery) and raw (a
proprietary, unprocessed, “negative” of your image i le). As raw i les are
exponentially larger than JPEG i les, many users i nd they can “buy” three to
four JPEGs for the cost of one raw i le, and thus never bother to explore the
many advantages raw capture has to of er. The raw format does have
signii cantly powerful advantages and those not (yet) shooting raw should
consider all of the following benei ts.
Raw i les are larger, but they are also uncompressed, high bit depth unaltered
originals. This means many things as you bring them into your imaging
application: i rst, you have the best image i delity that your camera can
muster, the greatest amount of capture information, and the most control
over image processing. Further, the raw format maps to the image settings
applied at capture, and every subsequent editing change applied in
processing, sits alongside the raw i le as an external reference component
associated with each image i le. Since changes and edits are not applied
directly to the raw image i le, all raw processing adjustments are completely
non-destructive and ini nitely editable.
Although programs like Adobe Camera Raw and Lightroom can now read
JPEGs, the application of controls such as “temperature” and “exposure” are
hacked into the JPEG i le artii cially.
While a raw i le contains the unprocessed and uncompressed image data
captured by the digital camera sensor, images captured in JPEG format are
compressed in the camera in order to make them smaller. This compression
process, known as lossy, is extremely destructive to image data. Artifacts can
easily be seen in magnii ed viewing on screen. In addition, both JPEG and TIFF
formats process the image data in-camera, manipulating the image data by
adding adjustments to all images unilaterally such as contrast and saturation.
For this reason, JPEG i les tend to look much better initially, but remove a
great deal of control over image processing. JPEGs also freeze applied capture
criteria and bake the settings into the pixels which, unlike raw, cannot be
undone. JPEGs can be extremely useful and benei cial if memory is essential, if
the number of images you can capture on a card must be increased, if general
pre-processing speed outweighs custom image processing, or if images are
destined for the web.
Keep in mind, however, that quality is signii cantly compromised in the
exchange. Best practice therefore is to use JPEGs when resolution and image
control are not as important, and use raw for everything else!