> 1. Is there a good reference to begin to learn about this subject?
Phil Davis has a good publication entitled "Beyond the Zone System"
I believe that it is in its 3rd edition now.
It is a progressive text that builds up a knowledge on all aspects of the
Zone System.
It has extensive discussion of the practical aspects of Densitometry
as they apply in the making of negatives and subsequent prints.
The book can be a difficult read since a lot detail is presented but it is
worth
the effort.
Before tackling Phil Davis's book, I would recommend reading a more
concise treatment of the Zone system. The best explanation I found
was in Ansel Adam's book on Polaroid Photography. It has been out of print
for a while, but your local library might have a copy. (Of course his other
publications *are* still in print and readily available and, are also
are good bedtime reading).
>2. Could someone summarize briefly the practical aspects of learning and
> using densitometry to analyze negatives and thereby improve the print
I think that others have answered this one quite well.
>3. If I decide to "get into" this densitometry thing; does it require an
> expensive densitometer; what type is recommended? are there alternatives?
There are two kinds of densitometers: reflection and transmission type. Some
models do only one others can do both readings. You will be using
transmission
type for negatives and reflection for prints. Modern units also have
separate channels
for measuring cyan magenta and yellow colours.
Of course you can use an expensive densitometer but you don't have to.
Phil Davis presents a plan that adapts a spotmeter for use as a densitometer.
If you befriend your local mini-lab they have the equipment to make these
readings from your negatives.
I know that a company called Darkroom Innovations, will make readings from
your
negatives. Darkroom Innovations also sells densitometers and a neat little
pocket computer that sets exposure times and development times for each
negative. Its programming is based on the Phil Davis book.
Finally, if you have *no* money, Kodak has a cardboard card that is covered
in
various calibrated grey tones. There is a hole in the middle of each grey
patch.
You visually match the shade of grey to the calibrated patch.
I found that it worked almost as well as a $1,000 reflection densitometer. I
am away from home now so I don't have the Kodak publication number for this
card. I think that it is a few dollars, but Kodak sent me a complimentary
copy a few years ago.
> 4. I have a line on a Tobias transmission TCX with digital readout; does
>anyone know anything about this particular instrument.
No, but before you buy it test it with a calibrated negative to check the
accuracy of
the unit. I know that X-Rite is a popular brand name especially at the
mini-labs.