Digital BW, The Print

Going through the last print exchange (I'm not rubbing this in but am 
studying it) - I noticed that several used the channel mixer to 
convert to greyscale.

Could a few people comment on why they might use the channel mixer 
vs. Image/Greyscale (dump color info) &/or simply desaturate?

Thanks,

Cleavis in AZ

> Going through the last print exchange (I'm not rubbing this in but am
> studying it) - I noticed that several used the channel mixer to
> convert to greyscale.
> 
> Could a few people comment on why they might use the channel mixer
> vs. Image/Greyscale (dump color info) &/or simply desaturate?

Control. 

When you use CHMX you control the blend ratio of the RGB channels. If your
original started out as color film this gives you a huge amount of tonal
control, less so if your original was BW. (In both cases a color scan is a
given however).

Image/grayscale is based on a blend of roughly 60% RED/ 29% Green/ 11% Blue.
Channel mixer allows you to choose your blend ration.

I'm not sure what desaturate is based on, but I'd guess it's the Luminosity
channel from LAB.

If it's not than that makes a fourth option. Additionally you could take any
single RGB or CMYK channel too, as another option.

Bottom line is that the other options just give you what they give you while
CHMX allows *you* to play with it. They're all viable options, and which
gives the best result may vary from one image to another.

If you have the interest to get into a channel by channel understanding of
PS I recommend Professional Photoshop 6, by Dan Margulis. Expect to read it
a couple of times. It ain't for the faint of heart, but it really gets into
the architecture of a digital image.

Todd

In the pre-digital era, photographers would shoot b&w film through filters
to achieve certain effects. They might use a red, green, or blue filter. Now
look at a color image in Photoshop using the Channels pallet to select the
Red, Green, or Blue channel (make sure "Color Channels in Color" is
unchecked in "Display & Cursors" Preferences). We can shoot in color and use
the channel mixer to achieve those filter effects.

Suppose you like the red channel's effect on the sky & the green channel's
effect on the trees - by using Photoshop's selection tools you can apply one
channel mix to the selection & another channel mix to the inverse of that
selection. Say you have a green & red shirt that when desaturated looks like
a gray shirt - use the channel mixer to increase the contrast between the
colors.

The Channel Mixer gives you control.  -BK

> -----Original Message-----
> From: Cleavis [mailto:lyonscox@...]
> Sent: Sunday, December 02, 2001 11:15 AM
> To: DigitalBlackandWhiteThePrint@yahoogroups.com
> Subject: [Digital BW] methods of conversion to B/W
>
>
> Going through the last print exchange (I'm not rubbing this in but am
> studying it) - I noticed that several used the channel mixer to
> convert to greyscale.
>
> Could a few people comment on why they might use the channel mixer
> vs. Image/Greyscale (dump color info) &/or simply desaturate?
>
> Thanks,
>
> Cleavis in AZ
>
>
>
>
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Todd,

> Image/grayscale is based on a blend of roughly 60% RED/ 29%
> Green/ 11% Blue.

I like the way you wrote that.  The more I read what you write, the more I
like you ;-)

Austin

on 12/2/01 7:14 PM, Austin Franklin wrote:

> Todd,
> 
>> Image/grayscale is based on a blend of roughly 60% RED/ 29%
>> Green/ 11% Blue.
> 
> I like the way you wrote that.  The more I read what you write, the more I
> like you ;-)
> 

You mean 'cause I'm getting to the point where my numbers actually add up to
100 ;-)

Todd

> > Todd,
> >
> >> Image/grayscale is based on a blend of roughly 60% RED/ 29%
> >> Green/ 11% Blue.
> >
> > I like the way you wrote that.  The more I read what you write,
> the more I
> > like you ;-)
> >
>
> You mean 'cause I'm getting to the point where my numbers
> actually add up to
> 100 ;-)
>
> Todd

Todd,

No, no, that wasn't what I meant...but that's pretty funny...I meant that
you put RED in all capital letters.  It is the devil's channel when it comes
to converting to B&W ;-)

%60 RED is just going to give you the mushiest grayscale image you can
imagine...you may as well shoot with a Holga!

Austin

on 12/2/01 7:24 PM, Austin Franklin wrote:

> 
>>> Todd,
>>> 
>>>> Image/grayscale is based on a blend of roughly 60% RED/ 29%
>>>> Green/ 11% Blue.
>>> 
>>> I like the way you wrote that.  The more I read what you write,
>> the more I
>>> like you ;-)
>>> 
>> 
>> You mean 'cause I'm getting to the point where my numbers
>> actually add up to
>> 100 ;-)
>> 
>> Todd
> 
> Todd,
> 
> No, no, that wasn't what I meant...but that's pretty funny...I meant that
> you put RED in all capital letters.  It is the devil's channel when it comes
> to converting to B&W ;-)

Opf, I didn't even notice I did that. That is funny. Just one of several
typos. ;-)
 
> %60 RED is just going to give you the mushiest grayscale image you can
> imagine...you may as well shoot with a Holga!

Legend has it that this was the ratio Tomas Knoll (sp?), who was the
original PS programmer, felt best emulated the tonality of Plus-X film -
(probably Plus-X *without* lens filtration).

But you're right, he was probably spoiled by drum scans. At least he kept
the Blue to a minimum. ;-)

Todd

I've been scanning my way thru 100+ sheets of 4x5 I shot in the Eastern
Sierra and Yosemite in October. It's mostly Portra160VC color neg, and
I've been using the channel mixer to get b&w. Sometimes I've used 100%
red,and often a a ratio close to what Todd said -- generally to get the
sky values where I want them.

At the start of the trip, I spent a weekend with Steve Kiser around Mono
Lake & Bodie. He was shooting with a Holga. :)

Richard Wolfson
rwolfson at LyricDesign.com
   Austin and Todd wrote:


  > > Todd,
  > >
  > >> Image/grayscale is based on a blend of roughly 60% RED/ 29%
  > >> Green/ 11% Blue.
  > >
  > > I like the way you wrote that.  The more I read what you write,
  > the more I
  > > like you ;-)
  > >
  >
  > You mean 'cause I'm getting to the point where my numbers
  > actually add up to
  > 100 ;-)
  >
  > Todd

  Todd,

  No, no, that wasn't what I meant...but that's pretty funny...I meant
that
  you put RED in all capital letters.  It is the devil's channel when it
comes
  to converting to B&W ;-)

  %60 RED is just going to give you the mushiest grayscale image you can
  imagine...you may as well shoot with a Holga!

  Austin


[Non-text portions of this message have been removed]

> I've been scanning my way thru 100+ sheets of 4x5 I shot in the Eastern
> Sierra and Yosemite in October. It's mostly Portra160VC color neg, and
> I've been using the channel mixer to get b&w. Sometimes I've used 100%
> red,and often a a ratio close to what Todd said -- generally to get the
> sky values where I want them.

Hi Richard,

What are you scanning them on?  If it's a CCD scanner, the red channel is by
far the worst of all three...it's typically about twice as fuzzy as the
green.  If you want to try scanning some of your film with my Leaf, which
scans B&W IN B&W (unlike most every other scanner, it does so by using an ND
filter, not scanning in RGB and converting), you're more than welcome to do
so!

Regards,

Austin

>
>  > Could a few people comment on why they might use the channel mixer
>  > vs. Image/Greyscale (dump color info) &/or simply desaturate?
>
>
>
>Image/grayscale is based on a blend of roughly 60% RED/ 29% Green/ 11% Blue.

Interesting. I have read that the Blue channel is especially prone to 
noise. But given what Blue or Green filters do to skintones in BW 
film photography, i.e exaggerate skin pigmentation and flaws, I'd 
have to guess those percentages were in part chosen to optimize skin 
tone reproduction. In a landscape image, more equal green/red might 
be better.

Optically, though, RG and B represent different wavelengths, and 
slightly different focus planes unless the optics are fully 
corrected, ala "apo" process and enlarging lenses. As green is mid 
spectrum, choosing it from RGB for grayscale, especially from BW 
negs, would seem to put the least demands on the scanner's lens. 
Comparing RG and B versions of a BW image might also reveal something 
about focus accuracy. Might well be different from scanner to 
scanner, too.



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