[filmscanners] Re: HP PhotsSmart - questions

["" <wbgilloolyjr@charter.net>]

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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