"Re: Re: physiology vs. sensitometry
-Comment: for help, contact stevea@sedal.usyd.edu.au
"Terry, I agree that the human eye can perceive a much wider range of tones
while
scanning and adapting to the details of the original scene than can be recorded
on film or even be printed on paper. We should ask an optician to know how much
it really is... ""
Nobody is disputing that. The question I have been asking is how wide a
brightness range can we perceive if we are at a single point and do not move
from it. No matter how much we scan, if an area is on zone 9 and the area next
to it is on zone 1 and we are looking at them both at the same time we will not
be able to see the detail in zone 1 although both can be recorded on film. If we
wish to record the scene as we saw it we would not include the detail from both
the extremes in the print. If we do make a print recording detail in both those
zones, and it is easily done by a skilful printer, something of the mystery of
the scene may be removed. A straight exposure from that negative can be printed
on platinum with some loss of detail in the shadows commensurate with our
natural visual abilities. We cannot do the same with silver gelatine. That is
what the spat was about.
And yes: a velvet-like platinum black may look deeper than the glossy bromide
black. But no: the rain-image with glittering lights I mentioned could not have
been printed the same way on bromide paper: On the bromide, I am sure, the
viewer would have searched the 'lost' detail in the shadows, because the
material is known to be 'perfect'.
The subjective reactions of an unknown observer ?
" I have in front of me an original Sudek
silver bromide print which I just got for restoration: Some kind of
impressionist, misty, soft landscape, sunset at a lake against the light with
some silhouettes of trees (undated). The first third of tones from white to
bright mid-grey in the sky and water and no detail in the black trees at all. I
am sure this print would be much more impressive, if Sudek had printed it in
platinum or gum. Now the shadows simply look dead and lifeless."
But they do not in the plates in my books. It is the mystery of those shadows
that often gives the prints their aesthetic appeal.
" And I am not
sure wether Irving Penn's platinums would look 'flat' when printed on silver
bromide paper. In fact similar prints - one platinum, one silver - were hanging
side by side in an exhibition I saw some years ago and they were all
'brilliant'. But the platinums somehow were on another level of perception..."
But to me many of them looked flat and had no mystery, while others, the
cigarette stubs, were, to m, beautiful. And I am not claiming that you have to
have a full density range in a platinum print.
"Peter Marshal wrote: "The number of tones is not really a measurable entity in
any case, but it is one of the choices we may make - if you like by the zone
system - on both silver and platinum prints.)
There are various tools we can use - such as step wedges. I think it is
important to realise what they do tell us and also their limitations.""
I suspect that there is no dispute between Peter Marshall and myself; it is just
that we are talking at cross purposes.
"Maybe that is an explanation of what makes the difference in the perception of
'perfect' bromide technology and 'imperfect' hand-coated materials: The better
the potential imaging quality (in a sensitometric sense), the less the viewer
accepts 'lost' tones and the more the photographer is forced to fullfill the
viewers requirements of seeing as much as possible from the original scene."
That is just one of the points. If the printer is presenting more than we can
see of the scene the viewer, he is imposing his own view of the syntax on the
viewer, and it is a distortion. The real point remains that platinum can accept
more of the scene, as we see it, directly from the negative than can the silver
gelatine print.
" The
'worse' the imaging quality and the less detail and tonal values are offered,
the more the viewer's phantasy is asked for, allowing to appropriate the image
to himself according to his individual experiences and imagination. That is what
both, Demachy and Kuehn had in common, although their photography was
different."
True
As I don't have my books around here in Dessau, I can't give the exact
explanation of the Weber-Fechner law. It says that to measure the
physiologically perceived difference between certain light or sound impressions,
you cannot compare just the amount of lux or db but have to use their
logarithms. Kuhn got the honorary doctorship from the Insbruck university
because he showed that a reversed s-shape curve in photographic materials would
apply better to human perception: Although we see reality according to the
Weber-Fechner law, we want to 'remember' it in (printed or painted) images with
contrastier shadows, brighter mid-tones and contrastier highlights.