In article <01bbd1e5$0e7846a0$06d76cce@Axion.axionet.com>, goldoil@axionet.com says...

>As a newbie to photography, I've often wondered why both film and video
>images are different in character than the human eye. Film seems to be
>darker, less sparkling in quality than the human eye (except Safeway flyers
>and promotional calendars). Video images seem to be brighter with less
>contrast than the human eye. And when I see movies on TV, sometimes I see a
>film-like broadcast image, very dark and lacking in detail, and other
>times, the broadcast image is very sparkling in detail and vibrant (this
>tends to occur when the major networks run feature films that were recently
>run on theatres). Was video processing done to enhance the film print so
>that it looks more detailed when shown on TV?
>
>Could anyone please explain these differences? And can't they make film and
>video respond like the human eye? Kind thanks to anyone who can shed some
>light on this.

Hmmm, an excellent question, put in an unusual (but helpful) way....
I think it has to do with what I call "brilliance", defined as the
brightness difference (or wideness of the range) between maximum dark
and light tones in the image. Starting with the eye (due to some "signal processing" in the brain), we are able to see all at once a brightness
range that can exceed 20 stops range - while at the same time keeping
good local contrasts for a snappy-looking, but tonally very wide-range
image. Trying to do this in photography in a medium that places the image
on a piece of paper (which has a very limited range between maximum black
and white) results in a great narrowing of the differences between adjacent tones (contrast) in order to fit the wide range of tones into the limited
span of brightness. Switching to transparency materials extends the
available brilliance somewhat, but it allows only a slighty extended
tonal range if the contrast is kept constant (and the available brilliance range is determined by the brightness of the light behind the film, and by
the maximum black of the film - which is why movies can look dark [Having
enough light behind the film to illuminate a very large screen at a
relatively great distance at a very high brightness level would vaporize
the film!]). TV images are capable of great brilliance and good contrast,
if the TV is set up to provide it. Slides viewed at short distances on
a good surface projected with high light-level output slide projectors
(or on a bright light table) can also provide high brilliance images.
In commercial products, like advertising, video tapes, display photos,
etc., manipulations are often done to enhance "snap" and appearance
of sharpness (ever notice how sharp car commercials can look on TV,
when the available resolution is only about 270 lines total in the horizontal direction?!). So, the image appearance results from the available brilliance of the medium used, the contrast selected, the
color quality available (and used), and the "signal processing"
(non-linear manipulations) employed in making the image.
Hope This Helps