Dynamic Range testing
Dynamic Range testing
- Subject: Dynamic Range testing
- From: "Phil lippincott" <email@hidden>
- Date: Tue, 11 May 2004 19:12:56 -0700
Hi Bob, Doug, Ernst, Jim, Rudy and Terry
After several years of doing scanner Density Range and Optical
Visibility Testing PMA (Photo Marketing Association International) and DIMA
asked for me to assist in "Scanner Round Up" testing for the scanner
industry. The review of the testing criteria and the assistance of conduct
of the tests included about 80 scanners so far and the assistance over the
years of about 15 manufacturers who assisted in running the tests. The
testing criteria, a comparison presentation and some of the results can be
reviewed at www.scannerforum.com
This testing effort has gone on for about 15 years. During this time we
tried a number of different targets. For density testing this included two
of the Stouffer targets. We found the Stouffer Targets to have variations
in density range within the same step wedge. Also a grainy presentation
when scanned with other than the most low resolutions. Perhaps this is due
to the silver halide contact printing grain-to-grain manufacturing methods
and Q' Factor mentioned in this thread. We however also determined that the
Kodak ST-34 Scanner Calibration target had none of the same issues. We also
determined that when the Kodak targets were read on an ISO Status A
calibrated densitometer that the printed values on the Kodak Target were
absolutely correct to the densitometer. Therefore we have without
hesitation used and been very succesful with the Kodak density target. As
for the actual testing results versus the wild claims made by scanner
marketeers regarding density responses greater than ISO Status A 4.0 These
claims should obviously unreasonable to most people. Simply there is no
commercial film with such high density, let alone any CCD scanner with
generously higher than Status A 3.2 Dmax density response. In comparison
unexposed and then developed Ektachrome film for instance has a Dmax of
about 3.6 or 3.7. Photo Multiplier PMT drum scanner hardware can get to
Status A density Dmax of 3.9. When considering density range Dmin is also
an interesting an often overlooked subject. Yes highlights count just as
much as shadows. Again PMTs can go down to .02 Status A density. Film is
about .08 to .10 and CCD scanners depending on their gain settings can get
down to between .15 to .40.
The best Optical Visibility "resolution" target is the U.S. Air Force
target. It simply allows you to scan at the scanners rated highest dpi and
then review the quality actually visible in the file of the visible line
pairs per milimeter. These testing results also produces very interesting
comparison to both manufacturer representations versus the absolute
outstanding quality of the films potentialyet often unrealized in scan
capture possibilities.
Sincerely,
Phil Lippincott
AZTEK, Inc.
www.aztek.com
--------------
>
>
>> Date: Fri, 07 May 2004 11:21:40 +0200
>
> From: Ernst Dinkla <email@hidden>
>
> To: email@hidden
>
> Subject: Re: Dynamic Range testing
>
>
>
> Jim Rich wrote:
>
>
>
> > On 5/6/04 3:39 PM, "Rudy Harvey" <email@hidden> wrote:
>
> >
>
> >
>
> >>Hi Terry, It was called the Q' Factor.
>
> >>
>
> >>You are correct , it is a very real effect, caused by dispersion of
the
>
> >>light path
>
> >>by film grain. It is another good reason to scan using oil. Using oil
>
> >>in effect , reduces
>
> >>the number of surfaces to 2 instead of 6(mylar-2 , film-2,drum-2)
>
> >>
>
> >>Yea, have not heard that mentioned in over 10 years.
>
> >>I just love terms like this , they only mean something to about 20
>
> >>people on the planet.
>
> >>
>
> >>All the Best
>
> >>Rudy Harvey
>
> >
>
> >
>
> > Rudy,
>
> >
>
> > Since you like those terms, perhaps some on this list might find this
>
> > spectrophotmetric tid bit interesting. In the early 1900s (1909) a
chap
>
> > named Callier created a formula for the relationship between specular
>
> > density and diffuse density. The formula is called Calliers Q factor.
>
> >
>
> > Jim Rich
>
>
>
> The Callier effect as we called it in relation to the behaviour
>
> of silver emulsions in point light enlargers versus diffuse light
>
> enlargers. There still could be a good reason to use a silver
>
> target in a scanner if it will be used for non-chromogene B&W
>
> film. The use of oil will not reduce the true Callier effect but
>
> can reduce a related effect of a matte film surface.
>
>
>
> Ernst
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