[filmscanners] Re: HP PhotsSmart - questions

["Arthur Entlich" <artistik@shaw.ca>]

OK, I give up, I'm beginning to sound like an echo in here...

You're just one step (or more) ahead on me each time I post... I best
read your replies before answering ;-)

Art

wbgilloolyjr@charter.net wrote:

> 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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