Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Ernst Dinkla" 
<E.Dinkla@c...> wrote:
> 
> 
> 
> >What is a good way to fine the proper focus for scanning on a
> 3200?
> 
> Sean<
> 
> I've made a spiral staircase of strips of slide glass 0.85 mm
> thick and on each step a brush stroke of grainy ink with some
> scratches through it. One side of the staircase starts at 0 mm
> and when turned over there's a 0.45 mm step first. So I can test
> the sharpness per 0.40/0.45 mm step. Best focus is approximately
> at 1.7 mm with my 3200. Others have found other distances from
> the glass bed.
> 
> The scanner has three planes where it should be more or less in
> focus. At the glass bed for reflective scanning, at 1 mm for the
> filmholder and at almost 3 mm for objects larger than the
> scannerbed (for reflective scanning again). Ideally it should be
> in best focus on the film at 1 mm and the DOF of almost 3 mm
> should take care of the reflective scans that normally are not
> scanned higher than at 600 ppi. I guess Epson thinks that the DOF
> will take care of the shifts in production tolerance as the
> actual focus can be higher or lower than the 1 mm above the
> glass. Finding the better focus isn't a dramatic quality increase
> but it helps especially when the scan is improved in Phothoshop
> later on. Even more important is the planerity that I get by wet
> mounting the film.
> 
> See Norman Koren's pages for the focusing measurements.
> 
> Ernst

Ernst, Sean

I did a test with slide glass on the 3200 and it was sharpest with 
the emulsion right on the scanner glass. Raising it the thickness of 
the slide glass softened it. So much for DOF and neg holders!    
Someone posted a test method of laying a ruler lengthwise on the 
glass with one end raised a few mm .  The prime was the sharpest 
point along the ruler.  

SilverFast allows variable USM sharpening and no sharpening.  I found 
that with zero pre-sharpening I couldn't get as crisp an image later 
with PS USM as I could with auto sharpen.  One thing to bear in mind -
 Epson 2400 & 3200 use a diffuse light source for film. This cuts 
film grain and dust but effects sharpening. 

Another concern is that all scans are RGB before conversion to 256 
grey. Does the pre sharpening effect each color differently?  Seems 
like: (1) pre-sharpening would toss out a lot of data conversion to 
256 grey could use. (2) sharpening after converting would 
be "cleaner" than doing three channels.   Looks like the trick 
already suggested is to find a combo, pre AND post sharpening 
technique, that suites the image. 

For the experience I'd like to try wet scans.  What is the chemical 
substance in the fluid?  Would Pec-12 work?  Seems very time 
consuming for occasional scans but for a large-volume scanner it 
would save spotting.  

RE quality of scan - it seems to me that, assuming operator skill is 
good, the difference between a scan of a 6x6 or larger neg from a 
E3200 and a N8000 would be tough to see in a  11 x 14  ink-jet 
print.  

I looked at the Epson 4870 at the store.  It has interesting film 
holders with milk-white plex above the film. The lamp travels the 
length of the film like a Umax.  I have a like-new 3200 for sale :-)

AZ


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