Someone recently asked if there was any discernible difference among the
low-medium-high settings with Ed's improved grain reduction filter in vuescan
7.2.3. I thought I'd try some small comparisons from a negative scan, a small
crop of sky and snow from a near-end-of daylight scene -- sky being a common
area where grain aliasing is noticeable and grain a reduction filter can assist
with image quality.
I think differences are noticeable. File sizes of almost same 200x200 pixel
crop are different: 28, 25, 23 and 21 KB for none, low, medium and high grain
filter setting (decreasing file size indicating a reduction in detail from the
filter action).
I also included the same crop processed by vuescan 7.1.23 and 7.1.25 (these
exhibit color differences too). The negative was scanned on a LS-30 at full
res (2700) using white balance color and IR clean. Six files are at
www.shomler.com/vuescan/
v7203n.jpg, v7203l.jpg, v7203m.jpg, v7203h.jpg, v7125h.jpg and v7123h.jpg are
approximately the same crop using, respectively vuescan grain reduction filters
7.2.3 none. 7.2.3 low, 7.2.3 medium, 7.2.3 high, 7.1.25 high and 7.1.23 high.
Scan was with IR clean on. There are some color differences between 7.1.23,
7.1.25 and 7.2.3. Scans are 48-bit mode, reduced to 24bit in photoshop 6.0.1.
Jpeg is from photoshop, compression maximum quality/12, color space AdobeRGB.
Complete image (September sunset on Mt. Shasta, California) may be seen at
www.shomler.com/other/0011329.jpg
Crop is from upper right quadrant.
--
Bob Shomler
