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7 Managing Photos
7.1 Some Remarks about File
Formats
Cameras and computers can store photos
in different file formats. Most use JPEG
compression because this decreases the file
size. As the JPEG compression process is an
irreversible data operation, this compression
is always related with a certain loss of
data. Nevertheless, for the vast majority of
applications, the JPEG format is sufficient and
delivers good results.
For professional or semi-professional
photographers it is sometimes important to
keep the whole information. Therefore some
cameras provide the possibility to store
pictures in RAW format. RAW files contain
all the information that the camera‘s sensor
recorded at the time of exposure, without
any compression or post-processing. In many
cases the RAW file also contains a scaled down
“thumbnail” version of the picture. Due to their
nature, RAW files are much larger and more
difficult to process. Although GVX can display
most types of RAW files, there are limitations
and not all features available for JPEG files can
be used with RAW files:
- In “Picture View” display mode, the GVX
will only display the RAW file‘s embedded
thumbnail. In most cases this is not a
problem as these thumbnails are large
enough.
- You can use the zoom function on RAW
files. But depending on the amount
of processing needed this may take
somewhere between 30 seconds and up to
a few minutes!
- RAW files can be used in slide shows only
when they contain an embedded JPEG
picture.
- RAW files can not be rotated.
-You cannot print RAW files from the GVX.
-You cannot add keywords to RAW files.
-You cannot use RAW files for the “Dust
Detection” feature.
Pictures that were originally scanned or
produced on a PC may be stored in TIFF format.
Most of these files will be decoded.
In case a TIFF file will not be decoded, the
reason mostly is, that a computer program
applied a proprietary compression to the file
and stored the result in a TIFF file structure.
7.2 Previews
Each time you want to view a picture, the GVX
performs a number of actions. The file is read
from the disk, then the JPEG file is decoded,
rescaled to fit the screen resolution and finally
color corrected to match the color space
used by the camera (sRGB or RGB). Each of
these steps takes some time. The higher the
resolution of the camera and thus the larger the
file, the more time it takes.
The GVX can however, if wanted, store the
final result of all these manipulations on disk.
For subsequent viewing the GVX can load this
“screen dump”. This increases the viewing and
browsing speed considerably. This method
is often called “caching”. There is no loss in
viewing quality. The only drawback is that some
amount of disk space is needed for storing the
previews.
7.2.1 Generate Previews
There are two ways to generate cached
previews:
Automatic: a preview is generated
automatically for each picture you view. For
details see chapter 5.2, “Device Settings” for
details.
Manual: You can instruct your GVX to generate
previews for the current photo album.
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