Scan2CAD raster to vector conversion software

Pass your mouse over the images below to see which scan was made by which scanner

Remember that the line / space cycles are so tiny they would look like a grey blur if you were to look at them on a printed T-10 resolution chart!

Conclusion

As far as we know this is the first comparative resolution test of popular wide format scanners to be published. The results will surprise some.

According to our eyesight (trying to count five individual lines in a test element), the Contex Hawk-Eye (200 dpi optical resolution) cannot resolve any of the test elements above. The Contex Crystal (508 dpi optical resolution) can definitely resolve test elements up to 6.3 line / space cycles per mm, possibly 7.1. All the other scanners (600 dpi optical resolution) can definitely resolve test elements up to 8.0 cycles per mm, possibly 9.0 and possibly even 10 in the case of the Graphtec CS600.

Some scanner marketing literature asserts that there is more to resolving power than optical resolution - the quality of the lenses etc., plays a big part. We accept this. But in the examples above, the lenses played their big part and did not produce the results that some might have been expecting. Certainly neither the Colortrac SmartLF Gx 42 (advertised as having a resolution of 1200 dpi) nor the Contex Puma (advertised as having a resolution of 800 dpi) offer visibly better resolving power in this test than other 600 dpi scanners.

The results would also tend to suggest that there is indeed a small difference between the 508 dpi Contex Crystal (advertised as having a resolution of 600 dpi) and scanners with a true 600 dpi optical resolution.

However, we are talking about tiny differences here. All the scanners except the Contex Hawk-Eye are capable of resolving lines that are so close together you can't resolve them with the human eye. We believe that this supports our view that the Contex Hawk-Eye's 200 dpi optical resolution is not enough for some CAD work. It also suggests that for all practical purposes, all the scanners in the test with a resolution of 508 dpi or greater have enough resolving power for CAD.

A final caveat. In this test, the T-10 chart was scanned in full colour. When you are scanning CAD drawings you will normally be scanning in black and white. This means that the quality of the scanner or scanner software's thresholding will affect whether it can resolve entities on a drawing, particularly if the drawing is dirty. So before buying a scanner, be sure to have test scans made with your own drawings!

Acknowledgements
We would like to thank Art Systems Ltd, Colortrac Ltd, Contex A/S, Graphtec GB Ltd and Image Access GmbH for making the scans used in this article.

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