Re: LS30 prescan

Andreas Rick (rickand@gemse.fr)
Wed, 28 Jul 1999 14:58:32 +0200

"Ewald R. de Wit" wrote:
>
> Andreas Rick (rickand@gemse.fr) wrote:
>
> > When you put the film strip into the scanner
> > (Strip of up to 6 24*36mm slides/negatives )
> > the scanner does a very quick scan of the whole strip
> > to find out and store the positions of all images.
>
> Are you positive about this? I thought the prescan was to
> establish the density of the images on the filmstrip and
> to use the optimal exposure time for each colorchannel
> (to fill the full bit range). It can do the positioning
> without prescan too so that's why I was wondering.

When I said "quick scan" I didn't mean the "prescan".
The "quick scan" happens when you put in the film without
sending anything to the scanner on the SCSI bus.
I called it "quick scan" as it determines already something
based on the images on the film - I'm not sure whether the
scanner is actually scanning.
As you said: "Prescan" - which you have to ask for by a SCSI command once
you have positioned the film on one image - is to find the exposure time.

> Btw, is there anyway a frontend could extract the proper
> RGB exposure times from you backend?

Not in version 0.4.2 but I am working on the problem.
Do you really need these values or would it be sufficient
if you can change the exposure time in percent of the optimal
value determined by the prescan as it was for the LS-20?
I ask because my current developement version pre0.4.3 can
only change the exposure values relative and I was wondering
if I need to do more.

-
Andreas

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