Re: aliasing was Re: filmscanners: Review of the Nikon CoolScan 4000

["Dave King" <kingphoto@mindspring.com>]

> "Dave King" <kingphoto@mindspring.com> wrote:
> > Do you mean jaggies are all through the image, or along the edges?
>
> The jaggies are through the entire image but are most noticeable on
high
> contrast edges within the image.  By "edge" I presume you mean the
outer
> boundary of the entire image.  The jaggies are regular slippage of
the
> scan lines in a sawtooth pattern.  They are apparently caused by the
> scanner mechanism moving at a particular speed - one which happens
> most often when using Nikonscan that scans in 64K blocks.  Ed has
> coded Vuescan to scan line by line with a delay to prevent the
> vibration that results in the jaggies.
>
> If you're lucky enough to have an LS2000 you could probably also
> eliminate the problem by using the multiscan option since it causes
> the scanner to scan each line multiple times, slowing the mechanism
> down.  The LS30 doesn't support single pass multiscanning.
>
> Rob

I asked because I wasn't sure what you referred to.  The term
"jaggies" is usually used to mean "pixelization", which of course is a
problem of too low resolution for a given output size, and it occurs
in all digital images at some point.

Nikonscan has two artifacts I can see, I believe both related to ICE.
One is the "serrated edge" effect caused by scanning film in mounts,
and it only occurs at the edges of the frame.  The other I'll call
"shark's tooth", and it looks like tiny spikes at regular intervals on
high contrast edges.  I think it only occurs in one direction, going
from memory.  To be clear what we're talking about, do you mean the
tiny spikes?  I'm asking for further clarification because from your
discription, "regular slippage of the scan lines in a sawtooth pattern
through the entire image", I'm not sure my particular scanner suffers
from this problem.

Dave