QUALITY SCANNING:
Creating high quality scans for raster to vector conversion
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Colour, greyscale or monochrome?
Most scanners give you the option of scanning in colour, greyscale or monochrome. These options have different names depending on the make of scanner you have.
Colour
Your scanner's colour option will normally create a scan that contains 16.7 million colours.
You should only use this option if you are scanning a colour drawing with a view to converting it to a colour vector file.
Take care not to use your scanner's colour option if you are scanning a black and white drawing. It is easy to do this by accident as most scanners default to colour.
If you are scanning a colour drawing with a view to converting it to a colour vector file, experiment with your scanner's settings until the colours on the raster image are as high contrast, vibrant and saturated as possible.
Note that colour scans can be very large. An E/A0 size drawing scanned in colour at 300 dpi will take up about 385Mb of memory.
Greyscale
Your scanner's greyscale option (often called black and white photo) will normally create an image that contains 256 shades of grey.
Greyscale scans are not normally suitable for raster to vector conversion and can be very large. An E/A0 size drawing scanned in greyscale at 300 dpi will take up about 128Mb of memory.
Monochrome
Your scanner's monochrome option (often called line art, black and white drawing or 1 bit) will create a much smaller scan that contains two colours - black and white.
This is the option you should normally choose when scanning a drawing for raster to vector conversion.
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Q&A: ASK AN EXPERT
Q: Do you know of any scanners that can output DXF files?
A: No, not one. No scanner creates DXF!
Scanning is a raster image process whereas CAD is a vector image process. The two are mutually exclusive.
The act of scanning breaks an image down into little squares, aka dots per inch (dpi) or pixels, basic raster elements. A scanned image is made up of hundreds of thousands of pixels. The higher the dpi, the greater the number of pixels. To get a DXF file from a scanned raster image you must use a raster to vector converter like Scan2CAD which will automatically convert the pixels into vectors (lines, arcs etc.) for editing in CAD.
Scan2CAD is a professional raster to vector converter. It is capable of generating more accurate vectors than similar programs but, like all other automatic raster to vector converters, Scan2CAD cannot achieve perfect results. Some tidying up in the CAD program will always be needed. If the combination of scanner and raster to vector conversion software is unacceptable, one alternative is to consider using a digitising tablet.
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