Re: shadow density in zone III

The problem with just making denser negatives is that it is a
generalization that makes no sense at all with many specific
combinations of films and processes, and in fact this practice can
have some negative consequences. It may make sense to overexpose with
films that have very long toes because increasing exposure puts more
of the curve on the straight line part of the curve. On the other
hand, films like TMAX-400 don't benefit at all from any increase in
exposure because the curve is already almost perfectly straight line.

Of course, some people deliberately over-expose on the rationale that
it is better to have too much shadow density than too little. But in
answer to your question, yes, there is a definite down side to
over-exposure in that it limits the maximum average gradient, or
contrast, of the negative, which can be a serious problem when
working with low contrast type films with low contrast scenes. Films
such as Tri-X and HP5+ are very definitely limited in their maximum
potential contrast, and if you waste some of this at the bottom of
the scale it can not be recuperated at the top with longer
development times. Once a film is developed to its maximum CI, any
further increase in time of development just gives denser negatives,
not more contrasty ones.

The Zone system is at best a very imprecise way of mapping
subject-negative-print tones and the testing procedures can take a
lot of time. If a person really wants to understand how to map these
values with any specific combination of film and process they should,
as Clay suggests, just bite the bullet and learn the language of
sensitometry. BTZS is a very good system for mapping values, but in
order to really use the system you need to have a basic knowledge of
sensitometry.

Sandy

>I just realized that I have another burning question about the zone
>system and zone III: what density is zone III in your negatives?
>
>For a long time I have been following Dick Arentz's suggestion that
>the density of zone III should be about .35-.4. But, as somebody
>mentioned earlier, very dense negatives can also make good prints,
>sometimes very good prints. If I raised the density of my shadows
>to, say, .70, then the highlights would have to be about 1.7, and so
>on. I have printed negatives like this and they look good. In fact
>it seems that the roll films that I have tested, if you shoot them
>at their rated speed and develop them at their recommended times,
>make denser negatives like that. Maybe that's to prevent people
>from underexposing their film. (But I normally shoot HP5+ in my old
>Rollei at 1600, in order to get the shadow densities down to .35 or
>.4.)
>
>Just curious: those people on this list that use densitometers to
>measure their shadow densities: what is your "goal" for your
>shadows? And what is the rationale behind that? Does it really
>matter what the density of the shadows is, as long as the highlights
>fall in the right place relative to the shadows? Maybe that .35-.40
>thing is completely arbitrary? And if there was a reason behind it,
>what is it?
>
>--shannon
Received on Thu Sep 29 10:01:46 2005