Sorry, I don't understand, if you have not use flash, your shooting positing
should not affect the exposure value. The only posssibility is the stage
lighting has power reduced.
C.H.Ling
----- Original Message -----
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
> ... in the auditorium that is. Some of you may recall this series of
> shots from my grandaughters' dance recital in 2007.
> <http://www.chucknorcutt.com/dance_recital_2007/index.htm>
>
> There was a similar recital in 2008 but I didn't like any of the shots
> and hadn't processed them at all. Actually, "didn't like them" is a
> serious understatement. Motion blur was everywhere due to low light
> levels and very slow shutter speeds. Finally my oldest granddaughter
> bugged me to prepare some 33 images for her where she either appeared in
> them or she liked them for other reasons. Those can be seen here:
> <http://www.chucknorcutt.com/dance_recital_2008/index.htm>
>
> In going through them I became even more painfully aware of the
> difference in light level between the two events but couldn't figure out
> why it should be. In 2007 I had set the camera at ISO 3200, shutter
> speed at 1/160 (for a 28-80/2.8 lens) and ended up shooting most images
> at from f/4 to f/5.6. In 2008 I tried the same thing but quickly found
> that I couldn't maintain 1/160 shutter speed. I was shooting at either
> f/2.8 or f/3.2 and at 1/80 or 1/60 second or even much slower. With
> fast moving dancers it was very difficult. I found myself trying to
> anticipate when the dancers would be be coming to a halt in order to
> reverse direction but not always very successful at all.
>
> Finally I extracted the EXIF data from all the photos from both years.
> I averaged the shutter speeds and apertures from all the images and
> found that there was approximately 1-2/3 stops difference between them.
> I also noticed that in the 2008 series that I had (very soon in the
> shooting) accidentally set a -1/3 stop exposure compensation level by
> brushing that silly big dial on the back of the Canyons because I hadn't
> locked the settings.
>
> The next question was: Why would there be such a great difference in
> illumination level? Certainly the light level varies from scene to
> scene on the stage but for the overall performance to have much dimmer
> stage lighting didn't seem to make sense. I queried Dr. Flash on the
> subject who reminded me that all light (not just flash light) falls off
> in proportion to the square of the distance. "I know", says me "but I'm
> pretty sure I was sitting about where I was the previous year". "Prove
> it" he says.
>
> I asked my wife where she thought we were sitting in 2008 relative to
> 2007. "I think maybe 3 rows further back" she says. That squared with
> my impressions as well. So I dragged out a couple images from both
> years, both shot at 80mm and compared the image height of people at
> center stage. Knowing their approximate height allowed me to estimate
> that the center of the stage in 2007 was about 40 feet away from us.
> But the center of the stage in 2008 was about 65 feet away. Well, that
> was a big surprise. 25 feet was a lot more than 3 rows back. In fact,
> that's about 1-1/3 stops. Close enough to tell me that my gross
> estimates of exposure and distance were close enough to explain the
> cause of the problem.
>
> So, when you take your camera into the auditorium sit as close as you
> can to the stage. Just like flash, seemingly small changes in distance
> can have a major effect on the amount of light you have to work with.
> In my case it went from pretty good to awful by moving back 25 feet.
>
> Chuck Norcutt
> (with assistance from Dr. Flash)
> --
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