Digital BW, The Print

Steve,

The data may be "clear", but really doesn't give you much information as to
what it really means as related to the actual image.

If you look at the histograms, as I've suggested, of an RGB scanned B&W
image, you will see, what may appear to you, as small differences.  Then,
take a look at the actual image, and thumb through the individual channels,
and you'll see a significant difference.  Point is, it's hard to quantify
the actual differences in an image using the histogram...it merely shows
there really are differences, but gives most people no real idea what the
visual impact of those differences may be.  Sometimes it's clear, other
times, not so.

I think the original issue is, as I read why Stan did this in the first
place, is to determine if his scanners B&W is better/worse than doing a scan
in RGB and converting in PS.  I can't draw any conclusion to that question,
as the data for the scanners B&W scan wasn't presented (do you happen to
have this, Stan?) along with the actual RGB data, and the RGB data all by it
self isn't enough.

Whether any scanner's B&W mode will give you equal results to RGB mode is
really scanner dependant, as every scanner will do this differently.  Almost
all scanners scan B&W in RGB anyway, and then convert based on some "canned"
mix of the three channels.

Austin


>
> Stan's data seem clear, but all I can say is that when I scan B&W
> film as rgb, for some negatives, using the channel mixer to convert
> to grayscale makes a big difference.
>
> Steve
>
>
> --- In DigitalBlackandWhiteThePrint@y..., "Shire,Stanley"
> <sshire@c...> wrote:
> > Austin:
> > That was the first thing that I did (look at the channels in the
> histo display)
> > tiny, tiny differences.
> >   ----- Original Message -----
> >   From: Austin Franklin
> >   To: DigitalBlackandWhiteThePrint@y...
> >   Sent: Tuesday, December 03, 2002 1:51 PM
> >   Subject: RE: [Digital BW] Re: Convert to B&W plugins
> >
> >
> >   Stan,
> >
> >   You can just scan the B&W negative, in RGB, and bring it into PS
> and compare
> >   the three channels.  You can compare RGB using the histogram, as
> well as
> >   compare them visually by hitting <ctl> ~, 1, 2 and 3...for All
> Channels,
> >   Red, Green, Blue...  Depending on the image, you will see
> anywhere from
> >   small tonal differences, to quite noticeable tonal differences in
> the
> >   different channels.
> >
> >   Regards,
> >
> >   Austin
> >
> >
> >   > -----Original Message-----
> >   > From: Shire,Stanley [mailto:sshire@c...]
> >   > Sent: Tuesday, December 03, 2002 1:21 PM
> >   > To: DigitalBlackandWhiteThePrint@y...
> >   > Subject: Re: [Digital BW] Re: Convert to B&W plugins
> >   >
> >   >
> >   > BW neg scans in color neg mode
> >   >
> >   > Quick on-the-fly-between-classes test results
> >   >
> >   > 35mm tmax 100 neg
> >   > Tmax developer
> >   >
> >   > The scans were made on an Imacon 848 and a Coolscan 1000 (I
> >   > figured that the greatest differences would show with these two)
> >   >
> >   > Both scanners set to scan at 8 bit, color neg mode.
> >   > Scan sizes were matched as closely as possible to 25mb
> >   >
> >   > 4 Markers placed in the same areas on each file. Tried to place
> >   > them in areas of differing densities.
> >   >
> >   > Imacon 848 scan
> >   > Marker    R    G    B
> >   > 1            22    22    22
> >   > 2            255    255    255
> >   > 3            240    234    234
> >   > 4            166    165    159
> >   >
> >   >
> >   > Nikon Coolscan 1000
> >   >
> >   > Marker    R        G        B
> >   > 1            5        5        4
> >   > 2            255    255    255
> >   > 3            206    199    186
> >   > 4            174    171    166
> >   >
> >   > Did not correct for density differences between the scans as I
> >   > wanted make no changes to the raw data as it came from the
> scanners.
> >   >
> >   >
> >   > Interpret this data as you will. My conclusion is that yes,
> there
> >   > are slight differences with red being higher in density than
> >   > green and blue being ther lowest density.
> >   >
> >   > The similar density differences between the two scans might
> >   > indicate a slight warm color in the film base.
> >   >
> >   > Big conclusion (YMMV): Very minimal difference between scanning
> >   > in RGB and GS modes.
> >   > Very minor tonal changes when converting with the ConvertToBW
> Pro
> >   > plugin. Not enough (if I were shooting a lot of BW film) to make
> >   > me go with a file that's 3x larger.
> >   >
> >   > Any thoughts appreciated.