RE: using a scanner as a densitometer?

Mark,

Doesn't the Stouffer have 21 steps? Each step 0.15, give or take a bit, and B+F around 0.05, should make the top step 3.05. Or are you talking about some other Stouffer?

Liam
-----Original Message-----
From: Ender100@aol.com [mailto:Ender100@aol.com]
Sent: 22 February 2006 19:09
To: alt-photo-process-l@usask.ca
Subject: 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

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