[filmscanners] RE: HP PhotsSmart - questions

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

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.



----Original Message----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk] On Behalf Of Arthur Entlich
Sent: Monday, August 08, 2005 4:45 AM
To: laurie@advancenet.net
Subject: [filmscanners] Re: HP PhotsSmart - questions

> The native optical resolution of this scanner varies
> dependent upon the size of the image being scanned.  In the
> case of 35mm film, which is just under 1" wide, the scanner
> sensor/CCD scans at 2400 ppi/dpi.
> However, when switched to reflective mode, the scanner can
> scan up to 5 x 7" prints (I previously incorrectly noted
> 4x6").  In this mode the maximum is 300 ppi/dpi (although the
> math implies it could scan up to about 450 ppi/dpi) but who
> knows what kind of optical light path bending they had to do to
> accomplish that.
>
> Art
>
> Laurie Solomon wrote:
>
>> I looked at the web site you gave the link for; it was not clear from
>> its contents as to what the unit's native optical resolution is.  If
>> the native optical resolution is 150 dpi and the other resolutions
>> are all interpolations, that might account for the reason that the
>> 150 is sharper than the 300 dpi.  Moreover, the screen resolution
>> might also enter into the equation since the screen rendering of the
>> image will be such as to make the 300 dpi scan be rendered on the
>> monitor at twice the size as the 150 dpi scan which can result it
>> some apparent fuzziness with the smaller rendering appearing sharper
>> even at lower resolutions.
>>
>> The standard rule of thumb sage advice is to scan at the scanners
>> optical resolution and not at an interpolated resolution to get the
>> maximum sharpness and the minimum flaws, artifacts, and noise.
>>
>> But you have me a little confused.  You speak of scanning a 3x5
>> print; but then you say you also had this negative roll scanned at
>> Target. Are we talking about positive paper prints or film
>> negatives?  They are two very different things.
>>
>> Unless you will be enlarging a hard copy print to a print size larger
>> then the original or a portion of a cropped print to the size of the
>> entire original print or larger, a 300 dpi is sufficient since hard
>> copy prints typically do not yield resolutions greater then 300 dpi
>> since the information is not there in the original to support a
>> higher resolution with actual original data.  To scan 35mm film, one
>> will normally scan it at a resolution of around 4000 dpi since the
>> frames will typically be enlarged to at least 3.5 X so as to produce
>> a 3.5 X 5 image at around 300 dpi.  A 1200 dpi scan of a 35mm film
>> frame is a relatively low resolution to be scanning 35mm at and
>> would require interpolation in the event that one wanted to enlarge
>> the image in its entirety or in part.  Thus, Target is really not
>> doing any better than your machine would do on a 35mm film frame.
>> Moreover, we do not know if the 1200 dpi that Target scans at is
>> real optical
> resolution or interpolated resolution.
>>
>>
>>> -----Original Message-----
>>> From: filmscanners_owner@halftone.co.uk
>>> [mailto:filmscanners_owner@halftone.co.uk] On Behalf Of Rich Koziol
>>> Sent: Saturday, August 06, 2005 1:01 PM
>>> To: laurie@advancenet.net
>>> Subject: [filmscanners] Re: HP PhotsSmart - questions
>>>
>>> On 6 Aug 2005 at 12:06, Laurie Solomon wrote:
>>>
>>>
>>>> As for the question of " why 150 dpi appears sharper than
>>>
>>> 300 dpi when
>>>
>>>> scanning a 3 x 5 color print," you did not tell us if the
>>>
>>> result you
>>>
>>>> speak of was on the monitor or on a hard copy print
>>>
>>> At this point I'm just looking at the results on a 19inch monitor.
>>> Used the HP software to scan with.
>>>
>>> I also had this negative roll scanned at Target, for comparison.
>>> Target offers 1200dpi scans for about $4/roll.  They just started
>>> this service and are still somewhat sloppy with film handling.
>>>
>>> Rich
>>>
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>>
>
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