I followed up with some observations to the thread originally posted as
There were some very informative follow ups to my post (thank you!) which
caused me to look further into the issue of yellow stains of on the edges of
scans from ACER Scanwit 2720s.
First I need to say I was wrong in my original post where I stated these
stains did not appear in my scans. I have now produced scans with this
effect and I am now distressed by what I see.
Second, this issue may also relate to the on going discussion around "grain
aliasing". See the web page below for example images.
Instead of posting everything I did and samples here, I have put the images
and dialog on a web page at http://www.theNichols.net/scanner and I hope
some of you will take the time to look at it and see if you have the same
issues with your scanner!
I also hope someone from ACER will take a look and respond - while the
Scanwit is capable of producing good scans from good negatives, I think
either I have a broken unit, or they have some problems in their
auto-exposure control system.
(Newbie - and probably completely confused - but I am not sure.)