multiple scan with SilverFast AI

[steven]

Hi,
I bought an Epson Perfection 4990 to scan (a.o.) 6x6 and 4x5 negatives.
I tried the multiple scan feature of SilverFast AI (demo). I scanned a 6x6
at 6400dpi in single scan and 4x scan. While the 4x scan shows less noise, I
found that the successive scanned images weren't well aligned, which results
in a final image looking like suffering from camera shake. Sharp edges are
gone. Under those circumstances one can expect to have less noise, but so
will (gaussian) blur.
So, not quite happy with first results.
Comments any1? Other experiences?
TIA

Steven

 

[Don]

Hi,
I bought an Epson Perfection 4990 to scan (a.o.) 6x6 and 4x5 negatives.
I tried the multiple scan feature of SilverFast AI (demo). I scanned a 6x6
at 6400dpi in single scan and 4x scan. While the 4x scan shows less noise, I
found that the successive scanned images weren't well aligned, which results
in a final image looking like suffering from camera shake. Sharp edges are
gone. Under those circumstances one can expect to have less noise, but so
will (gaussian) blur.
So, not quite happy with first results.
Comments any1? Other experiences?

Misaligned scans are a common problem when trying to scan the same
image multiple times in order to get rid of noise.

What you are really trying to do is known as HDR (high definition
range). Google for that to get more info.

If you search the archives there was a messages entitled "Twin scan" a
while back where one such method is described. Even though it has been
improved since, it's an introduction to the idea.

If you prefer an automatic solution you may want to try this free
program:

http://www.ict.usc.edu/graphics/HDRShop/

It has some shortcomings but you can start and experiment. Also, do
download the accompanying "tone mapping" plug-in to be able to export
the resulting image to regular TIF instead of the native floating
point format.

Don.