Perception of brightness (was Re: Good exposure)

[P3D <PTWW@xxxxxxx>]

>Gary Nored wrote:
>
>> More and more I am coming to believe that it is the SHADOWS
>> that determine our perception of brightness (at least as it is
>> recorded on film) -- not the relative brightness of the picture.
>(snip)
>> This experience, and others, have taught me to adjust the shadow exposure
>> in contrasty situations when I want to control the viewers perception
>> of brightly/dimly lit.
>> 
>> Just a thought -- or two
>
And Eric G. responds:
>
>And a very interesting one at that. This is clearly true for monochrome
>works, and I would agree that shadow is one of the key deliniators of
>light for color as well.
>
>The difficulty in practice comes with the narrow contrast range of film
>positive emulsions. It is less common to find an existing exterior
>composition with a contrast range within the 5-6 stops of slide film,
>and so practically adjusting exposure for the lower ranges places the
>higher ranges well above what the emulsion can handle.
<snip>

I don't know about anyone else, but the above exchange has left me
puzzled.  Gary states he adjusts the shadow exposure in contrasty
situations, but adds the qualifier "when I want to control the
viewer's perception of brightly/dimly lit."  In your shooting, Gary,
how often is your desire to control the perception of brightly/dimly
lit your dominant concern in caclulating exposure...as compared to,
say, recording as much detail as possible in both highlights and
shadows?  Does adjusting shadow exposure rise to the level of being
your general rule, or is it an exception for special situations?  I
have certainly seen slides where dark shadows *appeared* very well lit,
but the overall exposure was not particularly pleasing, *assuming* the
goal was to produce a "normal" or "realistic" image.

Eric, in noting your agreement with respect to "monochrome works," are
you referring to negative or positive film?

Eric goes on to point out that adjusting exposure for shadows pushes the
highlights well above what the (positive) emulsion can handle.  This
is the explanation I have heard as to why it is normally best when
shooting slides to "expose for the highlights and let the shadows fall
where they will."  And the reverse applies for negative film...expose
for the shadows and let the highlights fall where they will.  I suspect
most people think primarily of monochrome works as print format, which
makes adjusting shadow exposure a very good general rule. While I would
not expect it to make a good *general rule* for working with stereo
slides, I agree that it could be useful in the *special* situation
where the primary objective is to control the viewer's perception of
brightly/dimly lit, as Gary stated.

Paul Talbot, probably in the dark, but...


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