Digital BW, The Print

From: "Daniel Staver" <daniel@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Sunday, November 30, 2003 7:25 PM
Subject: RE: Re[2]: [Digital BW]  Banding on a scanner


> > I've recently started scanning Polaroid type 55 negs using an
Epson
> > 3200 with Vuescan and have not seen the banding you
described.
>
> The example was from the 9900 that I returned, with the 3200
it's less
> pronounced. Here's one I just made from the 3200:
>
> Converted to grayscale and increased contrast:
> http://daniel.staver.no/img/3200.jpg
>
> Original:
> http://daniel.staver.no/img/3200_2.jpg
>
> You'll see that the BW version has vertical banding in the sky,
while
> it's not easily visible in the original.
>
> Rotating the transparency 90 degrees on a scanner makes the
problem even
> less visible.
>
> --
> Daniel Staver
> http://daniel.staver.no

Several things can cause banding.

The Epson uses 3 sensor strips after another that are slightly
offset to one another so a higher frequency of sampling can be
achieved. The sensor may not be calibrated to one another like
they are not calibrated to one another on the Nikon 8000, the
last suffers of banding too. Very regular and more visible in
certain monotone grey fields than in other areas. Some 8000's
have it more than others if the reports of users can be compared
with one another.

Then there's a test by C't of the Canon and Epson where the Epson
scores bad on lighting evenness and the Canon not much better. I
have no answer yet to what that term exactly refers too but it
could be that the lamp doesn't have a constant output during the
scan. To be honest my 3200 doesn't show that problem.

Not related to this I think but I have observed that the
planerity of the film influences the light distribution on this
scanner. There's fall off to the sides when the film bulges
downwards.

http://members.chello.nl/e.dinkla/Verhaal.pdf

Ernst