Further comments and a different perspective:
John A. Lind wrote:
At 11:10 5/22/02, you wrote:
This is probably a dumb question, but when people say "negative film has
more latitude than slide film", which stage(s) are they referring to
where
you gain/lose latitude?
Latitude is the difference between how much light creates "pure white"
and how little creates "pure black" on the film. It is the ability to
capture detail in both highlight and shadow. The wider the separation
between the two (higher contrast), the wider the latitude required
from the film to maintain detail.
Light from the subject is 'mapped' onto a range of densities on the
film. There are 4 important characteristics of this map that bear on
'latitude':
1. Absolute latitude, the range between the brightest incoming light
which the film can distinguish from the next less bright step (see #3)
of light. and the equivalent lowest brightness it can record.
2. The range of densities on the film to which the latitude is mapped.
3. The resolution of latitude, the smallest difference in incoming light
level which can be measured as a difference in density in the processed
film.
4. The linearity of the mapping.
Comparing Color negative and transparency films:
1. Color negative film has wider absolute latitude than color
transparency film.
2. It maps this wider latitude to a slightly smaller range of densities
than does transparency film.
3. While there is a theoretical question about loss of information
through mapping a greater range of brightness into a narrower range of
densities, it seems it isn't a practical problem, probably, at least in
part, because prints have even poorer latitude and resolution. Anyway,
I've never heard complaints about color negative film that sound like
this would be the cause. (I have heard complaints on this list about the
lack of smooth density mapping in some B&W negative films.)
4. Linearity shows up in comments such as those about the way shadows in
one film 'go green' while those in another 'go magenta' etc. I'm sure
film engineers study it. I suspect is is a significant factor in what we
users see as subjective differences between films.
These differences have practical consequences for photographers. For
someone like John who primarily works with 'conventional' printing to a
medium that has a lower latitude than film through projection printing
and chemical processing, you can tell a lot about the image with light
table and loupe or a projector, whereas color negatives have a very high
'gobbledygook' factor when viewed directly.
For a photographer who primarily electronically 'processes' film images
by scanning them, negative film has some advantages:
1. It's wider latitude means it contains more total information about
the original range of light that came through the lens. This gives more
control over the contrast/brightness characteristics of the final print.
2. It's narrower latitude mapping occurs in such a way that it's highest
density (brightest light input) is less than the highest density in the
darkest areas of transparency film. Since current technology in film
scanners tends to produce noise in the form of random light pixels in
the densest areas of the film being scanned, it is easier to get a noise
free scan of negative film.
3. From the lack of 'noise' about it, I assume that the film has equal
or better latitude resolution than the scanners, so it is a non-issue
with current technology?
4. ????
Having the widest possible latitude is not always a Good Thing. In
low contrast scenes it can make the image look "flat" and often
"muddy." Contrast between highlight and shadow is one of the visual
cues that gives two-dimensional graphic images a feeling of depth and
dimension (there are several others). It also enhances object/subject
shape and surface texture.
Since I can control brightness and contrast and decide what part of the
latitude to retain and what extremes of the brightness range to discard
(in Photoshop or whatever), I prefer wide latitude in the film. The more
information I bring back on the film, the better off I am.
<big snip> A print is a photograph of the negative (or transparency).
Just as the photographer can make errors in focus and exposure, the
"printer" can also make similar errors with print density (same as
exposure), enlarger focusing and color balancing.
In the case of a transparency (technically 'reversal' film) the
transparency is a chemical 'print' of a negative image. The color
chemistry first develops a negative image very similar to color negative
film (but without the orange mask). It then chemically reverses the
image to a positive. I believe limitations in this process are
responsible for the lower latitude of reversal film.
Printing from transparency is much easier; the transparency itself is
a "witness" for print density and color balance; the print either
looks like it or it doesn't.
This is true, it is relatively easy to see if the print matches the
transparency, and one can do the same when using digital
scan/process/print from transparencies. In digital scanning of negative
film, I do something similar. I scan without any color or contrast
adjustment in the scan, to produce a relatively neutral digital
reference image to start with. (I also use Vuescan so the removal of the
color mask is specific to the film type to minimize color balance effect
from unmasking.)
It is important to distinguish this matching process from matching the
print to the original scene. There is no process, theoretical or
practical, which can reproduce in the eye and brain of someone viewing a
photographic image the 'equivalent originals' in the eye and brain of
the photographer. Read all the endless discussions about the objective
and subjective qualities of various films and you will see that this is
true. Take a whole bunch of shots of the same scene with different
transparency films, show them to a bunch of people who saw the original
and you will have an endless discussion about which one(s) more
accurately reproduce the original. They will, of course, be comparing
two types of imperfect chemical memory of an event which no longer exists,
Given this truth, I am quite happy to attune my prints from color
negative film to my fallible memory of the original scene. I think this
is no more nor less 'accurate' than the choice of transparency film with
which to take the picture and choice of filters to use in taking it.
I used to take slides for 'serious' pics and negative for the rest,
often carrying an OM with slide film and an XA with print film. Now I
use negative for everything. This is just one person's perspective and
your's will likely vary. I agree with everything John says, from one
perspective, and see shading of difference from others.
Moose
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|