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fields of information, 24-bit color and enhanced image quality
resolution. Video captured is about 7 minutes per Gigabyte.
It is also possible to adjust video settings such as bright
ness, contrast, saturation, hue, black level.
The capture of single frames followed a series of different
steps: digital acquisition of the analogical videorecording,
and then its display at 10 frames and at 1 frame. Because
of the low resolution of the outcoming images, four frames
were acquired instead of only one frame. So, the pixel size
on the object was reduced to about 1,5 cm, under the
same pixel size of the image (figure 1).
Then, the chosen frames were recorded and four digital
images were obtained. It is possible to export the images
as PICT or Quicktime files. In the present experiment, the
acquired images were exported as PICT files.
Regarding definition and loss of information, the quality of
the images was poor.
Acquisition by Avid MCXpress. Avid MCXpress is a soft
ware for personal computer that requires extra pieces of
hardware which are: Avid Broadcast Video Board, JPEG
advanced compression video board, Audiomedia III audio
board and an accelerator SCSI board two-way ATT/PCI.
The pieces of hardware used in the present experiment
were the following: video recording; TV monitor; computer
PowerPC Macintosh 9500; Ram 96MB; two units hard disk
in stripe AVID; a high- resolution monitor with a capability
to reproduce millions of colours.
With the above-mentioned software, the videorecording
was displayed on the monitor and the various settings
were adjusted (i.e. the radiometric calibration). It was also
possible to choose the format of television transmission
standard, Pal or NTSC.
The film was captured in digital format and then the
images to acquire were chosen by viewing individual
frames. It is possible to choose between one or two fields
of information. The images can be exported as PICT anti
aliasing, Quicktime or OMFI files. In the present experi
ment, two PICT files were exported, the first one with one
field and the second one with two fields of information.
The image with one field was better than the other one.
The pixel size on the object was about 1,5 cm (figure 2).
Acquisition by Avid Videoshop 3.0. Avid Videoshop is a
software that can be used with a personal computer fur
nished with an Audio Video (A/V) in and out system, with-
Figure 2 - Image Acquired by MCX Press
out additional hardware. The pieces of hardware used in
the present experiment were the following: video-recorder
Schaub-Lorenz HQ VHS 3 Head; computer PowerPC
Macintosh 8500, 604e 180 Mhz, Ram 64 Mb, HDD 2 GB,
Vram 4 Mb 128 bit, video Mac Picasso board (primary
monitor), Vram 2 Mb, 64 bit (secondary monitor), AV in and
out system; a high-resolution 17” monitor with a capability
to reproduce millions of colours.
The arrangement AV-in allows to connect the computer
with a video recorder and can turn an analogical video
recording into a digital one. Videorecording is viewed at
the monitor, in a window, and it is possible to adjust vari
ous settings such as brightness, contrast, saturation, hue,
black level, and to choose between different kind of com
pression. It is also possible to choose the format of the
video transmission standard, PAL or NTSC.
The film can be viewed at various speeds, the lowest at 1
frame per second. The acquisition of the selected frames
occurs in real time.
As in the previous case, four frames were acquired instead
of only one frame of the facade. The images were exported
as PICT files. The pixel size on the object was about 1,5 cm.
Analysis of Results Obtained. The captured images
were analysed and comparisons among them were made,
particularly about colour quality, sharpness, definition and
absence of blurring. The software Avid Media Suite Pro
provided poor image quality. As a result, these images
were rejected because they were not suitable for the pur
pose of rectification. The software MCXpress delivered
almost good images quality, but the best image quality was
that provided by software Avid Videoshop. Moreover, this
software is cheaper than MCX system, and it can be used
on a personal computer without purchasing extra hard
ware, a great advantage for home users.
Extremely important for the image quality, and particularly
for image definition, was setting the digital acquisition at the
lowest compression. It is also important the possibility of
setting the images with one or two fields of information. As
a matter of fact, the quality of a digital video image is deter
mined by its resolution, and by the number of fields or pic
tures included. The experiment demonstrated that the qual
ity of the images acquired with one field is better when they
are used as a static image, captured from a video, and not
as a frame of a film (moving images). Indeed, in this case
the one field image appears more definite and clear, and the
boundaries of the single objects on the image are sharper.
The images chosen for rectification were those produced
by Avid Videoshop. Before the rectification, the four
images were imported into Adobe Photoshop software in
order to reduce the different level of colours among the
four pictures, due to changes in the illumination of the
facade during the shooting (figure 3).
3.3 Rectification
The rectification of the four images was done by
Rolleimetric MSR. This is a software for the rectification of
metric and non-metric images, and for the automatic pro
duction of a mosaic. It is possible to check the precision of
single points, by collimating them on the video; it is also
possible to record the collimated points. The following was
used: computer PC Pentium 133 Mhz, Ram 64 Mb, HDD
2 GB, and a high-resolution 17” monitor with a capability to
