[alt-photo] Re: Print Density Estimation From Scan

[pfriedrichsen at sympatico.ca]

Eric,

I am not sure why any of this would matter if a step wedge is being 
scanned with the print? Can you elaborate on those questions?

Peter Friedrichsen



At 11:47 AM 12/10/2010, you wrote:
>Peter, What are you doing to lock down your base scan? What software and
>scanner are you using.
>
>Eric Neilsen
>4101 Commerce Street, Suite 9
>Dallas, TX 75226
>214-827-8301
>
>Let's Talk Photography
>www.ericneilsenphotography.com
>SKYPE ejprinter
>
>-----Original Message-----
>From: alt-photo-process-list-bounces at lists.altphotolist.org
>[mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of
>Peter Friedrichsen
>Sent: Wednesday, December 08, 2010 6:18 PM
>To: The alternative photographic processes mailing list
>Subject: [alt-photo] Print Density Estimation From Scan
>
>Hi All,
>
>Just wondering if anyone is willing to comment on my method of
>estimating print density using a scanner and a Souffer reflective step
>wedge.
>
>The density estimate is based on comparing only the red binary values
>with those of a Stouffer step wedge of 0.15 density increments per
>step, and this is done in photoshop by browsing pixels. The red
>channel was chosen because of an iron stain that affects
>predominantly the green and blue channels. The image I used is
>labeled print 3a and can be found here:
>
><http://picasaweb.google.com/pgfriedrichsen/FerricGumProcess#>http://picasaw
>eb.google.com/pgfriedrichsen/FerricGumProcess#
>
>
>The whitest area in the sky on the left side and about 1/2 way up
>gives me a value of 225. The first shades (lightest greys) above the
>left side of the roof give me 221, and the darkest shades just under
>the eaves troughs gives me 42. I have chosen to use the lightest grey
>values because there may be blown highlights and I don't want to
>include those in the density range. So, here is what I am using in summary:
>
>image density-----------pixel value-------step wedge # at this value
>
>lightest greys--------------221---------------less than 2 (use two as
>conservative)
>darkest greys---------------42---------------10
>
>difference density=10-2=8
>
>now I multiply 8.0 by the step density difference value of 0.15 per
>step: 8 x 0.15=1.2
>
>I get a density of 1.2.
>
>Anyone wish to comment on whether this is a sound technique for a
>reflective density measurement?
>
>Peter Friedrichsen
>
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