Digital BW, The Print

On 07-02-14 05:19, lestihor@... wrote:
> When scanning black and white 35 mm film with my Epson V750 Pro I
> found the focus not as sharp as expected. I tried scanning as colour
>  positive, then inverted in CS3. Then in Channel Mixer I applied in
> turn various coloured filters. I found that the blue or green filters
> produced very sharp results, while the yellow, orange and red filters
> produced progressively poorer focus. Does this mean that the scanner
> is focusing the red, blue and green scans in different planes? If so,
> is this a defect or is it normal?
>
>
> Les
>

Most of this you will know. First of all the V750 has no active
focusing. You have to find its sweet spot by adjusting the height of the
film carriers. It could be that for the V750's two lenses there is a
difference in height so carriers normally used for the 150mm wide scan
path get a different tweak compared to the wide carriers like the wet
mounting type. The 35mm carrier is just covered by the smaller field lens.
You might use only the two center strips and cover the outside strips
with black paper if there is some gain in that. Doug Fisher's Betterscan
(wet mounting) carriers are easier to adjust for focus. I wet mount
films on both the Nikon 8000 and the V700 that I have. Doug has a link
to something I wrote on wet mounting years ago.
Harder to do with 35mm frames. I think the V750 is not really up to the
task of scanning 35mm frames anyway, The 8000 here is used for 35mm
scans and normally dry but difficult takes get a wet mount treatment.

My theory is that flatbeds like the V750 use the lens with a very small
stop so near/in diffraction to cover the width of the scan path with equal
resolution. That and resolving "grain" or better to reduce "aliased grain"
goes along with using shorter wave light, Blue or Green. However Green
light lies in the middle of the spectrum the lens should cover so one
may expect better performance there, whether the focusing results in a
plane field is harder to conclude, though wet mounted larger frames scans
suggest it is quite plane. Deconvolution sharpening like one can find
in the smart "lens" sharpening in PS or ACR does a better job to
recreate the original information of the take than other sharpening
routines. It will reduce the flaws of both optical systems, of the
scanner and of the camera.

I use Vuescan with all my scanners. It's B&W scan setting favors the
Green channel. My method with the Nikon 8000 B&W scanning goes further
than that. The RGB LEDs can be controlled with Vuescan that only the
Green or Blue LEDs are used. Both gave better resolution than the full
RGB LED method. Right now I use the Green LEDs, wet mount, Vuescan DNG
RAW export but negative reversed to positive, PS ACR import and the
deconvolution (lens) sharpening used there. Grain reduced with Neat
Image in PS afterwards.

There are narrow band Green or Blue CCFLs that fall in the sweet spot of
sensor sensitivity for Blue and Green. If I can lay my hand on a cheap
secondhand V700 or V750 there would be a good chance I would replace the
white CCFL in the scanner's lid. A very nice dedicated B&W MF to 8x10
film scanner could be made that way.

So Yes, Blue or Green channels can make a difference.


-- 
Met vriendelijke groet, Ernst

http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
January 2014, 600+ inkjet media white spectral plots.