Let me try to clarify what I am asking.
I have 2 scanners, a cheap multifunction unit (scanner, printer,
copier,...), I know it has very little DOF. I also have an Epson V700 which
has much greater DOF. For something to be perceived as "sharp" by the human
eye, what is the size of the CoC required on a print ? I'm sure it was
mentioned on this list at some stage but can't remember the actual value.
The answer will determine how "deep" the object on the flatbed can be and
still be perceived as sharp by the viewer of a print.
...Wayne
Wayne Harridge
http://lrh.structuregraphs.com/
> -----Original Message-----
> From: Chuck Norcutt [mailto:chucknorcutt@xxxxxxxxxxxxxxxx]
> Sent: Saturday, 18 July 2009 12:58 PM
> To: Olympus Camera Discussion
> Subject: Re: [OM] Scanner DOF
>
> I'm really not sure I understand the question since I don't understand
> it in terms of DOF. Some flat bed scanners have a very great DOF of
> maybe 6mm or more from the surface of the glass which is great for
> scanning 3D objects. Others, not so much. So, the DOF is what it is
> and you won't be able to change it. It's not as though you can alter
> it
> by changing aperture or anything else except that some scanners can
> alter focus distance. So with the right scanner it might be possible
> to
> do multiple scans and blend the layers. But I don't know if scanners
> can really change focus distance enough to make that practical.
>
> But what I read into your question is something different. It sounds
> more like you're asking what scanning resolution you should use to
> maintain a good life-size replica of whatever you're scanning. For
> example, you want to scan a pencil which is 15cm long and print it on
> paper at 15cm while having it look nearly as sharp as the real thing
> when viewed from a distance of about 25cm. A resolution of 300 ppi
> should be adequate for all but Moose. If you want to please even Moose
> go to 600. Even he can't see better than that. :-) But remember to
> sharpen the final image at print size before printing.
>
> Dr. Focus
>
>
>
> Wayne Harridge wrote:
> > Probably a question for Dr Focus.
> >
> > I'm wanting to scan some 3D objects on a flatbed and wondering how
> much
> > depth of field I need. Assuming the resultant print is "life size"
> (i.e.
> > ~A4) what vale of circle-of-confusion should I be using. This should
> be
> > related to the resolution of the human eye at a normal viewing
> distance I
> > think - so what is that value ?
> >
> > ...Wayne
> >
> > Wayne Harridge
> > http://lrh.structuregraphs.com/
> >
> --
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