Vuescan: my new advanced workflow

I've been busting my brain trying to make Vuescan do what I want it to do.
Using the specified "advanced workflow" consistently produces muddy shadows
and never enough room on the toe of the curve. My new advanced workflow is
as follows: Preview, Lock Exposure at 1.0 (ie. ignore whatever value the
program comes up with), do a preview, lock image colors, presto plenty of
toe room for playing with in Photoshop's levels control. The only noticable
effect is that the Film Base values all seem to creep up a little. Anyone
else find Vuescan works best this way?

Im Posting von Alan Smithee <AlanSmithee@nowhere.com> stand:

> I've been busting my brain trying to make Vuescan do what I want it to do.
> Using the specified "advanced workflow" consistently produces muddy shadows
> and never enough room on the toe of the curve. My new advanced workflow is
> as follows: Preview, Lock Exposure at 1.0 (ie. ignore whatever value the
> program comes up with), do a preview, lock image colors, presto plenty of
> toe room for playing with in Photoshop's levels control. The only noticable
> effect is that the Film Base values all seem to creep up a little. Anyone
> else find Vuescan works best this way?

This depends largely on the used scanner. If exposure 1.0 is enough to
have the scanner look into the densest parts it will work. Most likely
it will not work for dense slides, but for C41 material, which has a
far lower density, it should, at least if the scanners standard
exposure is near to the optimum one.

For C41 I have another super-advanced workflow only applicable to Nikon
scanners: Do normal advanced workflow, then in color tab look at the
film base color values. Take the largest one and divide by the next
one. Take the result as a multiplier for the corresponding channel
analog gain value. Do the same for the remaining channel.

If f.e. your channels have film base color values: Red 0.9, Green 0.6
and Blue 0.5 the resulting analog gain values will be Red 1.0, Green
1.5 and Blue 1.8. Unlock film base color, do another preview and lock
again. The film base color values on color tab should be all more or
less the same. If they differ you can repeat the steps.

This way you get a pretty neutral negative. Now you can increase all
(locked) film base color values to 1.0 and scan the whole roll of film
with these settings. In my experience this neutralization of film base
color by different channel exposure works much better than the
mathematical one and you get almost clipping-free image data.

--
Erik Krause
Digital contrast problems: http://www.erik-krause.de/contrast

Erik Krause wrote:
> Im Posting von Alan Smithee <AlanSmithee@nowhere.com> stand:
>
>> I've been busting my brain trying to make Vuescan do what I want it
>> to do. Using the specified "advanced workflow" consistently produces
>> muddy shadows and never enough room on the toe of the curve. My new
>> advanced workflow is as follows: Preview, Lock Exposure at 1.0 (ie.
>> ignore whatever value the program comes up with), do a preview, lock
>> image colors, presto plenty of toe room for playing with in
>> Photoshop's levels control. The only noticable effect is that the
>> Film Base values all seem to creep up a little. Anyone else find
>> Vuescan works best this way?
>
> This depends largely on the used scanner. If exposure 1.0 is enough to
> have the scanner look into the densest parts it will work. Most likely
> it will not work for dense slides, but for C41 material, which has a
> far lower density, it should, at least if the scanners standard
> exposure is near to the optimum one.
>
> For C41 I have another super-advanced workflow only applicable to
> Nikon scanners: Do normal advanced workflow, then in color tab look
> at the film base color values. Take the largest one and divide by the
> next one. Take the result as a multiplier for the corresponding
> channel analog gain value. Do the same for the remaining channel.
>
> If f.e. your channels have film base color values: Red 0.9, Green 0.6
> and Blue 0.5 the resulting analog gain values will be Red 1.0, Green
> 1.5 and Blue 1.8. Unlock film base color, do another preview and lock
> again. The film base color values on color tab should be all more or
> less the same. If they differ you can repeat the steps.
>
> This way you get a pretty neutral negative. Now you can increase all
> (locked) film base color values to 1.0 and scan the whole roll of film
> with these settings. In my experience this neutralization of film base
> color by different channel exposure works much better than the
> mathematical one and you get almost clipping-free image data.

Very interesting. I'm going to try this. So to repeat what you've already
said.
1) go though the Advanced Workflow.
2) Divide Red base/Green base= 1.5, Divide Red base/Blue base = 1.8, which
yields working values of R=1.0 G=1.5, B=1.8
3) Unlock Film Base Color, Preview, Lock Film Base Color again.

What's going on with the RGB Exposure during all this?

"Alan Smithee" <somewhere@asdf.com> wrote in message
news:ElYye.1875764$Xk.596605@pd7tw3no...
SNIP
> What's going on with the RGB Exposure during all this?

The ratio of R, G, and B exposures is preset by VueScan when scanning
color negatives, and differs between scanner models. On Nikon Scanners
the ratio can be changed by the user. These ratios are supposed to
neutralize the color of the film mask.

Bart

Bart van der Wolf wrote:
> "Alan Smithee" <somewhere@asdf.com> wrote in message
> news:ElYye.1875764$Xk.596605@pd7tw3no...
> SNIP
>> What's going on with the RGB Exposure during all this?
>
> The ratio of R, G, and B exposures is preset by VueScan when scanning
> color negatives, and differs between scanner models. On Nikon Scanners
> the ratio can be changed by the user. These ratios are supposed to
> neutralize the color of the film mask.
>
> Bart

Good to hear from you Bart. I have an Epson 3200. I just see one RGB value
on my input tab, do Nikon scanners show three where I see one? What exactly
is the film base setting(s) doing? Does it adjust gamma or is it changing
the exposure ratio for each channel? In later releases of Vuescan I can now
choose to scan using just one color channel, doesn't this effectively give
me the ability to change the RGB ratio?

Alan Smithee <somewhere@asdf.com> wrote:

> I have an Epson 3200. I just see one RGB value
> on my input tab, do Nikon scanners show three where I see one?

Yes. They are called 'analog gain' but they simply are a channel
specific exposure multiplier.

> What exactly
> is the film base setting(s) doing? Does it adjust gamma or is it changing
> the exposure ratio for each channel?

None of that. It simply is subtracted from the pixel values.

> In later releases of Vuescan I can now
> choose to scan using just one color channel, doesn't this effectively give
> me the ability to change the RGB ratio?

Can't say anything about that, since I don't own an epson scanner...

--
Erik Krause
Digital contrast problems: http://www.erik-krause.de/contrast

Alan Smithee <somewhere@asdf.com> wrote:

> > This way you get a pretty neutral negative. Now you can increase all
> > (locked) film base color values to 1.0 and scan the whole roll of film
> > with these settings. In my experience this neutralization of film base
> > color by different channel exposure works much better than the
> > mathematical one and you get almost clipping-free image data.
>
> Very interesting. I'm going to try this. So to repeat what you've already
> said.

As I wrote previously this works only for Nikon Scanners that allow
adjustment of channels specific exposure ("analog gain")

> 1) go though the Advanced Workflow.
> 2) Divide Red base/Green base= 1.5, Divide Red base/Blue base = 1.8, which
> yields working values of R=1.0 G=1.5, B=1.8
> 3) Unlock Film Base Color, Preview, Lock Film Base Color again.
>
> What's going on with the RGB Exposure during all this?

It stays constant. Since the analog gain for at least one channel will
stay 1.0 and analog gain is an exposure multiplier it is a kind of base
exposure.

--
Erik Krause
Digital contrast problems: http://www.erik-krause.de/contrast

"Alan Smithee" <somewhere@asdf.com> wrote in message
news:Gpeze.1892120$Xk.1886357@pd7tw3no...
> Bart van der Wolf wrote:
>> "Alan Smithee" <somewhere@asdf.com> wrote in message
>> news:ElYye.1875764$Xk.596605@pd7tw3no...
>> SNIP
>>> What's going on with the RGB Exposure during all this?
>>
>> The ratio of R, G, and B exposures is preset by VueScan
>> when scanning color negatives, and differs between scanner
>> models. On Nikon Scanners the ratio can be changed by the
>> user. These ratios are supposed to neutralize the color of the
>> film mask.
>
> Good to hear from you Bart. I have an Epson 3200. I just see
> one RGB value on my input tab, do Nikon scanners show three
> where I see one? What exactly is the film base setting(s)
> doing? Does it adjust gamma or is it changing the exposure
> ratio for each channel?

Neither, it determines (in addition to the scanner default R/G/B
exposure time ratio) the scan's white-point clipping/settings (before
inverting to positive and Gamma adjustment). Only the Nikons can be
R/G/B exposure time ratio adjusted by the user.

> In later releases of Vuescan I can now choose to scan using just one
> color channel, doesn't this effectively give me the ability to
> change the
> RGB ratio?

Yes, but only if you individually/manually reassemble the R+G+B scans,
and without registration errors.

Bart