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finding the optimal exposure setting on high contrast scene?

Last response: in Graphics & Displays
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January 23, 2005 7:37:25 PM

Archived from groups: rec.video.desktop (More info?)

Whenever I videotape a stage show with my DV camcorder (a trv900), I always
have problem finding the optimal exposure setting.

I can't use auto exposure because due to the dark theater, this tends to
overexpose the actors. So I use manual.

Using the "zebra" pattern isn't perfect either. If I set the exposure so
that most objects do not have the zebra pattern, it usually end up
underexposing most objects because there are usually some very bright
objects on stage (e.g. an actor's white dress).

Using the LCD on the camcorder is no help either. Not only does it have
higher contrast than my TV (what seems like clipping on the LCD is actually
not), viewing it from different angle yields different brightness.

The only way I found is to haul in a small CRT based TV to use as a field
monitor. But even a small CRT TV is still very bulky. Is there a better
solution? Are there small LCD TVs with a much wider viewing angle than the
camcorder's and has adjustable contrast/brightness (so I can match it to my
TV)? How do the professionals do this? Do they have camcorders with wider
dynamic range?

I don't mind using post processing for minor correction. However,
underexposed video usually have poor S/N and overexposed video cannot be
fixed.
January 23, 2005 7:37:26 PM

Archived from groups: rec.video.desktop (More info?)

As you point out, over-exposure is fatal. Noise at the other end can
be managed. I think that's what makes a better (quieter) camera worth
the money - it still has the bright-end limitation, but survives the
dark end better.

Too bad there's not enough interest in the problem to create a
standard with a greater dynamic range. I'd guess it's not happening at
the CCD, else high end cameras would have high-end CCD solutions. But
the place the problem is worst - poorly lit 'stage' situations - are
of little interest to the larger community.

"peter" <nospam@nospam.com> wrote:

>Whenever I videotape a stage show with my DV camcorder (a trv900), I always
>have problem finding the optimal exposure setting.
>
>I can't use auto exposure because due to the dark theater, this tends to
>overexpose the actors. So I use manual.
>
>Using the "zebra" pattern isn't perfect either. If I set the exposure so
>that most objects do not have the zebra pattern, it usually end up
>underexposing most objects because there are usually some very bright
>objects on stage (e.g. an actor's white dress).
>
>Using the LCD on the camcorder is no help either. Not only does it have
>higher contrast than my TV (what seems like clipping on the LCD is actually
>not), viewing it from different angle yields different brightness.
>
>The only way I found is to haul in a small CRT based TV to use as a field
>monitor. But even a small CRT TV is still very bulky. Is there a better
>solution? Are there small LCD TVs with a much wider viewing angle than the
>camcorder's and has adjustable contrast/brightness (so I can match it to my
>TV)? How do the professionals do this? Do they have camcorders with wider
>dynamic range?
>
>I don't mind using post processing for minor correction. However,
>underexposed video usually have poor S/N and overexposed video cannot be
>fixed.
>
>
Anonymous
January 24, 2005 4:47:42 PM

Archived from groups: rec.video.desktop (More info?)

On Sun, 23 Jan 2005 16:37:25 GMT, "peter" <nospam@nospam.com> wrote:

>Whenever I videotape a stage show with my DV camcorder (a trv900), I always
>have problem finding the optimal exposure setting.
>
>I can't use auto exposure because due to the dark theater, this tends to
>overexpose the actors. So I use manual.

The spotlight auto setting may work OK. Better than using the
default, it tries to make a very bright small area have normal
exposure, and others darker.

>Using the "zebra" pattern isn't perfect either. If I set the exposure so
>that most objects do not have the zebra pattern, it usually end up
>underexposing most objects because there are usually some very bright
>objects on stage (e.g. an actor's white dress).

Since overexposure is fatal -- you can never get back the details
within that area -- this is about the best you can manage on manual.
If the brightest objects are just shy of overexposure, you've done
what you can.

>Using the LCD on the camcorder is no help either. Not only does it have
>higher contrast than my TV (what seems like clipping on the LCD is actually
>not), viewing it from different angle yields different brightness.

LCD quality varies, the newer ones have better TV-like contrast, but
otherwise, it takes some practice to learn how to interpret it.

>The only way I found is to haul in a small CRT based TV to use as a field
>monitor. But even a small CRT TV is still very bulky. Is there a better
>solution? Are there small LCD TVs with a much wider viewing angle than the
>camcorder's and has adjustable contrast/brightness (so I can match it to my
>TV)? How do the professionals do this? Do they have camcorders with wider
>dynamic range?

Only a CRT looks like a CRT. There are small nicer LCDs, but I
don't think you'd gain enough from going to them rather than a CRT.
The built-in LCD is much more convenient.

Pro cameras don't have more dynamic range per se. What they do have
is variable gamma, the ability to brighten the darker areas without
affecting the brighter spots. You need enough low light detail
collected with the CCD in order for this to give any true increase in
detail.

You can do the same thing via post processing.

>I don't mind using post processing for minor correction. However,
>underexposed video usually have poor S/N and overexposed video cannot be
>fixed.

The only solution to poor S/N is a camera with better low light
gathering ability. Without changing cameras, and with no influence on
the scene lighting (the lighting director could add more lights for
video recording), the manual method you've been using, using the zebra
to spot the brightest areas, is about as good as you can do. Doing a
close in zoom in order to set the exposure on the actors, then leaving
the exposure set manually, can work *if* the stage lighting remains
fairly constant.


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