Re: "Older" scanner better than new!

[Signal <signal@xxxxxxxxxxx>]

Rob Morley <nospam@xxxxxxxxxxxx> wrote:

>> Just an observation more than anything else, but when my "old"
>> parallel interface scanner packed up I replaced it with a Packard Bell
>> usb one that worked fine. However, with my old scanner I could use it
>> to scan decent pics of 3D objects. i.e. it was able to focus on parts
>> of an object a cm or so above the top of the scanning glass. The new
>> one however fails do this.
>
>It depends on whether the sensor is CIS or CCD.  A CCD scanner is like
>a digital camera (except its sensor array is only one pixel wide and
>it uses mirrors to get the image to the lens) and as it has similar
>optics it has depth of focus - objects not actually touching the glass
>bed but within an inch or two of it still appear reasonably sharp.  CIS
>doesn't use lenses, the sensor is directly below the glass bed and each
>cell captures the light reflected from the object immediately above it
>- as soon as the object is raised a little the adjacent cells also
>catch some of that reflected light and the captured image becomes
>blurred.

Indeed..
http://www.canon.com/technology/canon_tech/category/scan.html

Last time I bought a scanner (few years now) I sought a CCD
specifically to be able to capture with some depth. The brochures
don't exactly warn you about this difference, easy to get caught out..

Went for a CanoScan 3200F in the end, really like it to this day. They
go for about £25 on ebay.





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