Re: [Leica] Mitchell Colorbrator (was Enlarger Lenses)

["Gary Todoroff" <datamaster@humboldt1.com>]

After Bill asked me about the Colorbrator in a private e-mail today, I
thought maybe the LUG might be interested in this discourse on a useful
little enlarging tool:

> From: Bill Welch <
> 
> 
> Gary, I was interested in your post on this subject on the LUG . . . 
> How do you like the Mitchell Colorbrator and PM2M? I'm doing color
>printing with my CPE2 and judging by eye. I've been wondering about both
of >those items, and if you find them useful. 

Hi Bill -

Interesting timing to your post. I just talked an hour ago to Glenn Evans
in Chicago to order a custom dichro head that will fit both my 1c and D3.
The 300 watt bulb should blast thru those Velvia shadows on 16x20's!

The Mitchell Colorbrator is simply a standard slide or negative of
"ring-around" colored boxes and can be used without a color analyzer. You
expose the Colorbrator slide (or color neg) onto a 4x5 sheet of paper with
the
recommended filter pack, develop and dry (I use a microwave with Ilfochrome
test prints for quick results). Then use the Mitchell gray "Comparator" to
find true neutral gray in one of the 49 "ring-around" colored boxes, which
vary by 5cc in all color directions. Then use the chart in the Mitchell
booklet to see how many cc's the gray box is removed from the true neutral
gray box in the middle of the ring-around boxes. Adjust your filter pack
that many cc's and repeat until you get the middle box to create a true
gray. After that, your regularly lighted flash or daylight photos should
print very well.

With a color analyzer it is simpler. 

1. After your first Colorbrator test print, put your color probe under the
projected colored box that the Comparator says is true gray. Then adjust
your
color analyzer CYM dials to "zero" in the gray. 

2. Now move the analyzer probe to the Colobrator projected colored box at
the center ("real" gray). Adjust your *filter pack* until the analyzer
reads "zero" again (don't adjust anything on the *analyzer*). Bingo, you
now have an adjusted filter pack for your enlarger and paper that will
print a perfect copy of the Colobrator (altho you don't need to do that)
and will also print properly anything that was photographed under "normal"
lighting. You may need very slight adjustments for different brands of
color transparencies. I don't know about color neg.

As an alternative to step 2, you can look for neutral gray on your
actual slide or neg which you want to print. Put your analyzer probe under
that projected piece of gray in the image, and adjust the filter pack to
get your analyzer to read zero. For example, if you shoot in a mixed
lighting situation, be sure to photograph a neutral gray card somewhere on
the roll under that set of lights. Then use that test photo slide or neg to
adjust your filter pack until the analyzer reads zero (according to how you
set it up in step 1 above). The neutral gray card doesn't even have to be
in focus or very large, just properly exposed and big enough that your
probe can read it. If you start taking color pictures under a different set
of lights, then just take another shot of your gray card and adjust your
filter pack for it before doing prints of the actual photos in the
different light.

This is a nutshell of a series of articles by Bob Mitchell in "Photo
Techniques" two or three years ago - I think the title was "Everything I
know about Color Printing."

I talked to Bob Mitchell 2-3 years ago when I bought a Colorbrator from him
over the phone. He seemed like a real nice guy, and I was sad to hear that
he died about a year ago. I think B&H and others still carry the Colobrator
tho. Be sure to specify whether you want slide or neg version.

Hope this helps some LUGgers besides Bill. . .

Gary Todoroff
Tree LUGger