Chemicals & Equipment -GLScan
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GELLIFTER SCANNER |
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Digital imaging has made major inroads in crime-scene units and forensic departments all over the world. Digital photography has many advantages over traditional photography: savings on material costs, film development, storage space and time. Results are available instantaneously and, if not satisfactory, a new image can be taken immediately.
However, there is one downside: the resolution of certain images. In most cases, like shots of a single fingerprint or overviews of a crime scene, the resolution is sufficient for the intended use. A problem is encountered when a shoeprint needs to be photographed. Enlargement of this kind of trace may result in dpi (dots per inch) resolution that is low and unsuitable for making comparisons.
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Using a 5.2-megapixel camera to photograph a Gellifter sized 13 x 36 cm will produce an image with a resolution of 180 dpi.
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Image captured with:
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Resolution:
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5.2-megapixel camera
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180 dpi
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35-mm film*
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494 dpi
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GLSCAN
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1046 dpi
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* BASED ON 15 MILLION LIGHT-SENSITIVE GRAINS PER NEGATIVE
In comparison: a 155-megapixel camera would be needed to capture the same image with a resolution of 1000 dpi.
High resolution
With the GLSCAN (Gellifter scanner), traces obtained by Gellifters are recorded in a high resolution. The GLSCAN is the first system to be specially designed for digital recording of traces lifted with black Gellifters.
Its operation is of such simplicity that even 'non-professional photographers' will obtain excellent results. The GLSCAN captures images with a resolution of approximately, but not less, than 1000 dpi. This high resolution makes it possible to view (on screen) or print greatly enlarged details. On a 21" monitor, the image is enlarged about 11 times when viewed at 100%.
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Gellifter size
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File size
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9 x 13 cm
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23.7 MB
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13 x 18 cm
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39 MB
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13 x 36 cm
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86 MB
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18 x 36 cm
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114.6 MB
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Perfect illumination
The GLSCAN is equipped with three individual light sources that provide for an even illumination of the complete surface of the Gellifter. Two of these sources are specially for the scanning of black Gellifters. They produce light of high intensity and enable the capture of even the weakest traces. The Gellifter is kept perfectly flat on a vacuum table while scanning is in progress to avoid unwanted reflections giving rise to hotspots in the image.
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Shoeprint on black gelatin lifter,
scanned with GLScan.
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Distortion-free results
Distortion of an image, the so-called fish-eye effect, is limited to the absolute minimum with the GLSCAN. A cleverly placed high-quality lens ensures an image that is distortion-free along both the x and y axes.
The right results quickly
In contrast to traditional photography, in which a lot of effort is spent finding the correct illumination and exposure time, developing film, et cetera, the GLSCAN is very efficient. A shoeprint is scanned in less than 2.5 minutes. The image is automatically saved on the hard disk of the connected computer. If an image processing program is installed, the scanned image will be opened directly in that program for evaluation and adjustment/fine-tuning.
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Gellifter size
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Scantime
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9 x 13 cm
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70 seconds
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13 x 18 cm
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105 seconds
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13 x 36 cm
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145 seconds
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18 x 36 cm
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145 seconds
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Operating
The GLSCAN is operated by a PC running Windows XP. The command window on the screen is well-organized and simple to operate allowing choice/selection of scan size, illumination, whether vacuum is used during scanning, and the camera sensitivity (gain). Case and item number can be entered for use in the file name of the image (important for archiving). Additional data can be entered, such as place and date/time of obtaining the evidence, which is stored together with the image file (EXIF information in the TIFF format).
Archiving
The images captured by the GLSCAN are automatically saved on the hard disk of the connected computer.
With entry of a new case number, a new folder (subdirectory) is made with the case number as name. Each image name combines the case and item numbers with "_ref" and the "tif" extension, i.e. casenumber_itemnumber_ref.tif.
This 'raw' image is stored as a "read-only" file and can be viewed as the negative in traditional photography.
Delivery
The GLSCAN is delivered with an up-to-date computer (Windows XP) and a 21" rotating monitor, GLSCAN software, a vacuum pump and two vacuum tables of 13 and 18 cm width (maximum scan length 36 cm). Each vacuum table is fitted with a ruler on a long and a short side. Image processing software is not included.
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Detail of scanned shoeprint
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Untreated fingerprint on black gellifter, scanned with the GLScan.
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“Tests to date have demonstrated that the system is highly effective in the imaging of latent footwear marks lifted using black gel lifts, with good quality images being obtained from marks barely visible to the eye. The technique has also been used to image latent fingerprints lifted from surfaces where it is suspected that contamination is present and powdering may not be effective.”
Pages 6 & 7 of HOSDB newsletter |
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 GLSCAN brochure (1.5 MB).
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