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<p>Thanks for the additional info.</p>
<p>I don't have a machine running Windows so USB captures from that
platform aren't possible at the current time.</p>
<p>Jon</p>
<div class="moz-cite-prefix">On 7/31/26 12:18 PM, Ralph Little
wrote:<br>
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cite="mid:119f625d-f8d1-44af-b727-8e35ec6665a8@gmail.com">
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Hi,<br>
There are other backends that support transparency but the genesys
chips are pretty much a world of their own. On the upside, the
GL646 is pretty well documented.<br>
I believe the main ways in which the transparency support would be
invoked would be via the source and options related to capture
type. I don't see any specific image capture type-related options
in the backend but some would have to be added I suspect (e.g. for
selecting between positive and negative, IR etc).<br>
<br>
The main challenge with genesys-based devices is that every model
is different to every other in implementation. The Genesys chips
are very flexible and offer all sorts of driving options and they
need to be set up for the particular hardware that they are
matched with. The main way to tackle this task is to observe
Windows driver behaviour through capturing traffic and looking at
the register values that are set. It's a little more involved but
that is the main gist.<br>
<br>
I have had some dealings myself with looking at a GL646 device
before although it was a fairly superficial look at motor stepping
tables but I may be able to look at it in the future sometime.<br>
One thing you *can* do (if you have the inclination) is to make
some USB captures on Windows and post them to an issue at our
GitLab issue tracker (<a class="moz-txt-link-freetext"
href="https://gitlab.com/sane-project/backends/-/work_items"
moz-do-not-send="true">https://gitlab.com/sane-project/backends/-/work_items</a>),
if you don't intend to do the implementation yourself. That way
someone could pick up the issue at some point. Ideally a developer
needs the hardware at hand, but a rough stab could be made by
looking at the traffic.<br>
<br>
Cheers,<br>
Ralph<br>
<br>
<div class="moz-cite-prefix">On 2026-07-31 10:01, <a
class="moz-txt-link-abbreviated moz-txt-link-freetext"
href="mailto:7xsuazlhhtls@gmail.com" moz-do-not-send="true">7xsuazlhhtls@gmail.com</a>
wrote:<br>
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cite="mid:2d3d1219-1365-4b09-a4ea-feeb08e72f10@gmail.com">
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<p>Ralph,</p>
<p>Thanks for the reply.<br>
<br>
I looked at the Genesys Datasheet for the chip (GL646USB) that
is used in the HP4850. I see the register that appears to
control the slide scanning lamp.</p>
<p>Is there another backend that has support for a similar
feature? Possibly I could use that as a template to better
understand how support for this feature might be implemented
in the genesys backend.</p>
<p>Thanks again,</p>
<p>Jon</p>
<p><br>
</p>
<div class="moz-cite-prefix">On 7/31/26 11:21 AM, Ralph Little
wrote:<br>
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<blockquote type="cite"
cite="mid:7c8c105f-1b7d-4461-8a20-e6cb83788192@gmail.com">
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Hi,<br>
According to our Supported Scanners list (<a
class="moz-txt-link-freetext"
href="http://www.sane-project.org/sane-supported-devices.html"
moz-do-not-send="true">http://www.sane-project.org/sane-supported-devices.html</a>)
the genesys backend doesn't yet support the slide scanning
feature of this device. It requires additional code to drive
the extra hardware involved.<br>
We don't have an active maintainer for the genesys backend at
the moment unfortunately, so I don't know when someone would
be able to get to this task in the future. :(<br>
<br>
Regards,<br>
Ralph<br>
<br>
<div class="moz-cite-prefix">On 2026-07-30 20:58, <a
class="moz-txt-link-abbreviated moz-txt-link-freetext"
href="mailto:7xsuazlhhtls@gmail.com"
moz-do-not-send="true">7xsuazlhhtls@gmail.com</a> wrote:<br>
</div>
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cite="mid:d0f9e851-d9f4-44fd-b3c2-eb6699345df3@gmail.com">
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<p><code>I recently acquired an HP Scanjet 4850 scanner.
The document scanning works with no problems. This
particular scanner has a negative/slide scanning
component built in to the lid of the device. This
includes a separate lamp to illuminate the film for
scanning. The lamp in the lid comes when I run a
hardware self test procedure but I have not discovered
any way to have the lamp come on when scanning using
sane.<br>
<br>
Is this capability supported?<br>
<br>
info about my setup ---<br>
<br>
HP Scanjet 4850<br>
<br>
$ scanimage -V<br>
scanimage (sane-backends) 1.4.0; backend version 1.4.0<br>
<br>
genesys backend<br>
<br>
Fedora Linux 44 (Workstation Edition)<br>
Linux 7.1.5-200.fc44.x86_64</code></p>
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