Re: using a scanner as a densitometer?

It is not too difficult to get fairly accurate densitometer readings from
your scanner, as long as you have a standard reflection step tablet to use as
your standard comparison—these are available from Stouffers.

I included this feature in the new PDN Curve Calculator II just as an added
tool and it is surprisingly accurate—compared to my reflection densitometer the
values varied no more than about Log .02 reflection density. You just enter
a measured value between 0 and 255 and the software converts it to a Log
value for you.

The main trick is setting black and white endpoints properly using the
reflection steptablet and then saving that setting to use later with whatever you
are measuring. You then compare the Photoshop Values of the print densities
you are measuring to the known values of the reflection step tablet. You can
easily create an Excel Spreadsheet that will convert this data for you.

Note that the maximum value on the Stouffers is Log 2.0 reflection, so unless
someone knows of a reflection steptablet that goes above that value, you are
limited to values between Log .03 and Log 2.0 when using this method.

Best Wishes,
Mark I. Nelson
www.MarkINelsonPhoto.com
www.PrecisionDigitalNegatives.com
PDNPrint Forum @ Yahoo Groups
Received on Wed Feb 22 13:09:44 2006