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RE: filmscanners: LONG; Is: AcerScanwit but also generic calibration was: AcerScanwit

Well, since we have Acer listening now, I cannot but make a request:

Mr. Honda Lo and all the rest of interested filmscanner list members,

I have a 2720 that does not function properly. The problem is probably
background noise in the CCD. During calibration only the responsiveness to
the white light is calibrated for each CCD pixel. I think you can compare it
to determining the whitepoint for each pixel. I would like to have added the
blackpoint too. (I.e. read the response from the CCD with no light reaching
the CCD). Of course this would imply changes to the firmware if at all

I mailed Ed Hamrick on this issue and he agreed after several mails that the
error I was seeing is indeed a CCD response issue, but he could not help me
with added functionality to calibration (blackpoint calibration) as the
hardware of the scanwit does not offer a means yet to do so.

I think that is sensible to have first of all my Scanwit repaired, I have
the scanner for app. 10 months now so perhaps it's all under warranty, but
secondly it would be a nice feature if scanner calibration (regardless of
which brand) would also be done for both black and white point for each CCD
pixel. This may be especially useful after aging of the scanner.

Thank you in advance for your thoughts and time,

Jerry Oostrom

For the interested ones a part of the mail discussion with Ed and an example
(if the list lets me send it) of a negative scan out of many scans in which
the error is shown: yellow bands across the long edges in scans from
negatives (especially bad in the wedding dresses on my homepage's members
only section) and with regard to diafilm: light bands across the long edges
of dark dias (examples see windmills and airplanes page of my homepage:
mail 1:
        Dear Mr. Ed Hamrick,
        once again I have a question for you.
        My scanwit 2720 has a peculiarity. I believe it is the lamp that
does not function at 100%.
        As a result my scans look bad across the long side at the borders of
the frame: negative scans become yellowish there, which is especially bad
for buildings, white dresses and as in the example I sent you: snow. The
prominence of this problem is much more apparent when I use your software if
compared to Miraphoto (Scanwit's own software) which is probably due to your
software being of better quality. 
        Can you confirm that it is the lamp that is giving me problems? Or
is it some sort of reflection against the negatives.
        I have attached the vuescan log, the vuescan settings, a 4x
downsized crop file and an 8x downsized scan file. Scan was done using
version 7.0.3
        Is it possible for you to do a calibration that would countereffect
this behaviour? I.e. a calibration that takes into account the pixel
readouts for each pixel along the short edge of a scan.
        Should I place a piece of clear film in the small rectangular cutout
used for the calibration? 
        Is it possible to do a calibration against a whole frame (filled
with a clear negative)?
                Or is there something I can do with raw scans in a
photoeditor which will subtract e.g. a raw scan of a clean frame from a raw
scan with photocontent and then reread the result in Vuescan to get the
right colors?
mail 3:
        In a message dated 3/30/2001 1:51:54 AM EST,
Jerry.Oostrom@Alcatel.nl writes:

        > Is Vuescan automatic calibration performed only with the scanner
lights on
        >  or is it done with both scanner lights on and off?

        It's done exactly the same way as the Acer software - with the light
        The calibration data is read when the film holder is all the way
        the scanner.  It reads the CCD at the small, rectangular slot in the
        film holder.  If you have anything blocking this slot (i.e. film),
        calibration will be messed up.

        Ed Hamrick 
mail 5:
        In a message dated 3/30/2001 3:20:04 AM EST,
Jerry.Oostrom@Alcatel.nl writes:

        > no,  I haven't got anything blocking this slot. Please believe me
in this: I
        >  have not yet placed anything in the calibration slot and the slot
is still
        >  as it came from the factory: i.e. OK.

        I believe you, but it was worth checking.

        >  Is it possible and sensible for you to do a calibration as it is
done now 
        >  get the CCD response for lights on and add a second part to the
        >  in which you read the CCD for background noise (i.e. with the
        >  obscured) and integrate both readings in the scanner response?

        No, this isn't possible.  The way the hardware works is that I need
        to do it the current way - there's no provision for what you're
        for in the hardware.

        You might consider having your scanner serviced, since the
        problem occurs both with VueScan and with the Acer software.

        Ed Hamrick

> -----Original Message-----
> From: Honda Lo [SMTP:HondaLo@acerCM.com.tw]
> Sent: Tuesday, April 03, 2001 8:10 AM
> To:   filmscanners@halftone.co.uk
> Subject:      RE: filmscanners: AcerScanwit
> Importance:   High
> Best Regards,
> Honda Lo
> Product Manager / Sales of acer Film Scanner
> acer Communication & Multimedia / PGA

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