Vuescan problem?
I recently spotted a problem with some of my scans on the Plustek 7500i, using Vuescan Pro (version 9.7.76 initially). I had scanned a roll, and printed off a few candidates, preparatory to posting on twitter (my resolution this year). Close inspection of one print showed some really odd vertical line artefacts near some high contrast edges:
Blow up of image section
I’ve been in correspondence with Ed Hamrick, the author of Vuescan. He asked me to try older versions. So far we have established that the problem was certainly occurring early last year:
(When I first saw this feather image, I was very confused, but decided it must have been some sort of weird ice effect!)
The last version I could find that did NOT show the problem was 9.4.67.
Since my Plustek started to be a bit unreliable registering second passes (resulting in weird, sort-of-double-exposure scans), I have been scanning at twice the desired resolution and using the “reduce by 2” option in the output tab. Specifically, I usually want 2400 samples per inch scans, so I’ve been scanning at 4800 spi.
We have established that the problem occurs:
- at 4800 reduced by 2
- at 4800 not reduced
- at 7200 reduced by 4 (which produces both vertical and horizontal artefacts)
- at 4800 reduced by 4 (which only produced vertical artefacts)
The problem does not occur:
- at 7200 not reduced
- at 3600 not reduced
- at 3600 reduced by 2
So all that is pretty weird. IMHO the problem is likely due to a change in the reduction/interpolation algorithm that allows non-native resolutions etc, but that is speculation and un-confirmed.
At the moment all is quiet from Ed; I haven’t heard if it’s my problem or Vuescan’s (I did do a scan with a trial version of Silverfast 8, but it didn’t allow me to select 4800, which I think is NOT a native resolution for the Plustek). I have just asked him a follow-up question.
My last roll I scanned as I used to, ie a 2400 spi scan with two passes, and it worked OK, so I may do that again today.
So, my advice? If you have been scanning with Vuescan Pro in recent years using non-native resolutions or the size reduction option, I would go back and look closely at some of your scans. These artefacts are generally not very noticeable at first glance (the feather above was an exception), generally just giving a feeling of surprising softness to the image. Look particularly for edges at a slant. I have found the problem in all sorts of images once I looked more closely!
I will keep you informed.