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Re: [OM] Be careful where you sit...

Subject: Re: [OM] Be careful where you sit...
From: John Hudson <OM4T@xxxxxxxxxxx>
Date: Sat, 03 Jan 2009 21:45:46 -0400
----- Original Message ----- 
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
To: "Olympus mail list" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Saturday, January 03, 2009 9:16 PM
Subject: [OM] Be careful where you sit...


> ... 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>


Wow !

jh



> 
> 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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