On 12/4/01 2:30 AM, EdHamrick@aol.com <EdHamrick@aol.com>, wrote:
>In a message dated 12/4/2001 2:07:36 AM EST, julianv@mindspring.com writes:
>
>> Here are two sample scans (one from VueScan, one from Nikon Scan) that
>> show the benefit of a manually selected focus point:
>>
>> <>
>
>No, there are too many other differences for this to be a useful
>test. It isn't clear if sharpening has been applied to the NikonScan
>result, and the range of intensities is different in the NikonScan
>and VueScan images which makes them look different.
As it says on the web page, no sharpening was applied to either image.
The only adjustment I applied was a small tweak (using Photoshop's levels
tool) to reduce a blue cast in the Nikon Scan image.
To my eyes, the differences between the two images are more than
intensity/contrast differences. There are details visible in the NS
version which are blurred or totally absent in the VS version.
>A more useful test would be to first use the Advanced Workflow
>suggestions to lock the exposure, film color and image color.
>
>Set "Device|Auto focus" to "Scan" and scan the whole slide.
>Then crop to a smaller area and scan again with auto focus
>on the smaller area. Then change "Device|Auto focus" to
>manual and manually offset the computed focus value by some
>numbers while scanning the smaller area.
I am not sure that I understand your methodology, probably because I am
unclear on how VS determines the focus point. How do I set "autofocus on
the smaller area"? I do not know where VS is choosing the autofocus
point, and I know of no way to change it. Is the autofocus point always
at the same point on the slide, or does it change when the crop or region
rectangle is changed?
You said in an earlier message that VS sets the focus point at one third
of the way in from a corner. A corner of which rectangle? (total scan
area? region rect? crop rect?) Which corner? One third of the way to
what? (to the center? opposite corner?) Does the corner change,
relative to the image, when VueScan is set to rotate or mirror its
display?
How do I "manually offset the computed focus value"? Do you mean that I
should change the "Auto focus" popup menu to manual, and enter numbers in
the "Focus" box, rescanning and comparing the focus at each position?
--
Julian Vrieslander <mailto:julianv@mindspring.com>
