[filmscanners] RE: HP PhotsSmart - questions

["Laurie Solomon" <laurie@advancenet.net>]

> If the optical resolution is variable and YES there are
> scanners that can do it

I will take your word for it; but according to my understanding, the optical
resolution has little to do with the distance between the lens and the
sensor and more to do with the size and capacity of the sensor.  The
effective resolution may change with the changes in the distances between
the lens and the sensor; but the actual native hardware optical resolution
remains the same.  But I could be wrong in my understanding; I am not an
engineer.

> If the resolution is variable and the scanner can achieve
> 2,400ppi over a 1" wide path, then it will achieve 480ppi
> over a 5" path (2,400ppi/5in = 480ppi simple arithmetic).
>
> You can set up a simple ratio if the original strip is
> something other than 1"...
>
> Original Resolution         New Resolution
> ___________________     =   ___________________
> Original Scan Width         New Scan Width

What?  I do not come out with that using your formula.  Original Resolution
of 2400 with an original scan width of 1" versus New Resolution of X with a
scan width of 5 inches gives me a New Resolution of 2400 x 5 or 12000
ppi/dpi using your formula.  The only way I could get what you got is to
divide the Original Resolution by the New Scan Width to get the New
Resolution which is not what your equation says.

However, if the scanner does have variable native hardware optical
resolutions, the 2400 ppi/dpi tells us about the film native optical
resolution and not the native optical resolution for reflective print scans
(i.e., if it is the same or different).  Thus we do not know if the scan
width should be applied to the native optical resolution for film scans
versus that for prints.

> -----Original Message-----
> From: filmscanners_owner@halftone.co.uk
> [mailto:filmscanners_owner@halftone.co.uk] On Behalf Of
> wbgilloolyjr@charter.net
> Sent: Monday, August 08, 2005 2:55 PM
> To: laurie@advancenet.net
> Subject: [filmscanners] Re: HP PhotsSmart - questions
>
> If the optical resolution is variable and YES there are
> scanners that can do it (they have to be able to change the
> distance between the lens and CCD (CMOS) to change the
> resolution, then be able to move the Lens-CCD assembly into
> the new focus position.  Needless to say, this generally is
> in the realm of higher-end scanners.
>
> If the resolution is variable and the scanner can achieve
> 2,400ppi over a 1" wide path, then it will achieve 480ppi
> over a 5" path (2,400ppi/5in = 480ppi simple arithmetic).
>
> You can set up a simple ratio if the original strip is
> something other than 1"...
>
> Original Resolution         New Resolution
> ___________________     =   ___________________
> Original Scan Width         New Scan Width
>
> Fill in what you know and solve for what you don't.  It works
> every time, IF the scanner has variable resolution (many
> don't).  Remember, you can never exceed the maximum optical
> resolution of the scanner.
>
> Mr. Bill
>
>
> Laurie Solomon wrote:
> > Maybe my math is bad; but if it has a native resolution of 2400
> > ppi/dpi scanning 1" film, then my math says it will have a native
> > resolution scanning a 5 inch subject which is much lower than 300
> > ppi/dpi independent of the light path factors(e.g., around 75
> > ppi/dpi). For the size print that the original poster
> mentioned which
> > was smaller ( but I forget the exact size but I think it
> may have been
> > either a 3.5 x 5 or a
> > 4 x 6), the native optical resolution would be in the range
> of about
> > 150 ppi/dpi to 300 ppi/dpi.
> >
> > But this is based on the assumption that a scanner can have
> variable
> > native optical resolutions; however, to the best of my
> knowledge and
> > understanding, scanners have a single native optical
> resolution.  The
> > effective optical resolution is a by-product of the number
> of inches
> > that one divides into the native optical resolution.  Thus, an
> > enlargement of the image without any interpolative resampling will
> > result in a lower effective resolution while the reduction of the
> > image size without such sampling will result in a higher
> effective resolution.
> >
> > Nevertheless, it is still unclear to me if you are saying that the
> > native OPTICAL resolution of this scanner is variable or
> not; and if
> > not, if the native OPTICAL resolution of this scanner is
> 2400 ppi/dpi
> > or something else that would produce an effective native
> resolution of
> > 2400 ppi/dpi when scanning a 1 inch horizontal length as opposed to
> > some other horizontal length.
>
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