Digital BW, The Print

Those are Newton rings. They occur when the film curls.  Heat causes the film's emulsion to shrink and the film to curl in a concave shape.  The backing is only 1mm away from the glass bed for an Epson scanner if the film is perfectly flat. When it curls it can bring the center portion of the film in contact with the glass bed.  Newton rings only occur towards the center of the film, near where the film makes contact and disappear towards the edge where the film is kept away from the carrier.  A little humidity prior to the scan will curl the film in an opposite way so that the scanner lamp will curl it back to flat during the scan.  The same happened with the Canon scanner you returned, it was not defective, sorry Canon!  Reversing the film will make the rings disappear since the curl will bring the central portion of the film away from the glass bed however there will be slight degradation in the image.  The sharpest results will be with the emulsion facing up. I turn the scanner off after the scan to prevent the lamp from heating the films too much.  With Silverfast the transp light goes off when the image is transferred to PS but it lights up again during prescan and stays lit until the scan and transfer and that can be ample time for curling to develop. If you do not want to turn the scanner off, remove the film in the carrier or the carrier from the scanner to prevent additional curling.

Julio Fernandez
  ----- Original Message ----- 
  From: Daniel Staver 
  To: DigitalBlackandWhiteThePrint@yahoogroups.com 
  Sent: Sunday, November 30, 2003 11:31 AM
  Subject: RE: Re[2]: [Digital BW]  Banding on a scanner


  > No banding on the negs, also I have made gelatin silver 
  > prints in a wet darkroom that look fine. David Aschkenas

  I get banding in the light sky areas of my 6x7 transparencies scanned
  with the Epson 3200. I had the same problem, but even worse, with my
  previous CanoScan 9900f, and returned it for that reason.

  Does it by any chance look something like this?
  http://download.petraflux.com/img/streaks2.jpg

  --
  Daniel Staver
  http://daniel.staver.no




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