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

Subject: Re: [OM] Be careful where you sit...
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Sun, 04 Jan 2009 11:41:10 -0500
This discussion of light sources vs subjects has made me realize that I 
don't understand the physics of the situation at all.  I can readily 
understand why a point source like the sun has its intensity drop off as 
the square of the distance.  A fixed quantity of light is expanding to 
fill an ever larger virtual sphere whose surface area is increasing 
according to the square of the radius (4*pi*r^2).  What I don't 
understand is why, once the light has struck and reflected off the 
subject, why the subject is not treated as the "light source" for the 
reflected light that's emanating from it in the same sense as the sun is 
a light source.

Chuck Norcutt


C.H.Ling wrote:
> I mean you stack two RAW developments of the same image.
> 
> C.H.Ling
> 
> ----- Original Message ----- 
> From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
> 
>> Sound fine for a static subject with the camera on a tripod.  :-)
>>
>> Chuck Norcutt
>>
>> C.H.Ling wrote:
>>> If you need to reduce the overall exposure to avoid the faces from 
>>> burn-out
>>> that means you have over exposed your images. The background of the scene
>>> could be dark but your subject is the people so you should expose for it. 
>>> To
>>> bring some shadow details out you may max two different developed images,
>>> one exposed for the people and the other slightly increase the exposure a
>>> little bit.
>>>
>>> C.H.Ling
>>>
>>> ----- Original Message ----- 
>>> From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
>>>
>>>> Good thought but I think my chance of talking to the stage manager is
>>>> about zero.  It raises an interesting question in my mind about how the
>>>> DVD turned out.  This event is always recorded on video and a DVD is
>>>> made available for sale after the event.  My son doesn't buy it because
>>>> it's too expensive and my granddaughter is only on stage for about 5-10
>>>> minutes out of a 2 hour long production.  I just wonder how the video
>>>> cameras (with long lenses shooting from the back of the auditorium) fare
>>>> under the same lighting conditions.  Actually, since they do sell the
>>>> DVD, I have been surprised for the past two years that they have never
>>>> objected to me coming in with the 5D and a big lens.
>>>>
>>>> After adjusting the color temperature for most shots into the 2800-3500K
>>>> range the overly bright red was considerably subdued but still too
>>>> bright to be completely recovered with just the "recovery" slider in
>>>> ACR.  Most of it could be handled by dropping the overall exposure along
>>>> with the recovery slider but then the overall exposure was much too 
>>>> dark.
>>>>
>>>> The 5D treats me well most of the time so I think I'll keep it despite
>>>> its shortcomings.  :-)
>>>>
>>>> Chuck Norcutt
>>>>
>>>>
>>>> C.H.Ling wrote:
>>>>> May be you can talk to the stage manager, @ ISO3200 F2.8 1/60s is just
>>>>> too
>>>>> dark for enjoying the performance! The Chinese Opera I just shot was
>>>>> having
>>>>> a minimum light level of ISO400 F4 1/60s, four stops brighter than 
>>>>> yours.
>>>>>
>>>>> For the difference in RGB channels, did you set the WB to 2800-3200K?
>>>>> Some
>>>>> lower power stage light may be just too warm. Finally, if everything 
>>>>> just
>>>>> didn't work out, send me your 5D and purchase a 5D Mark II, which 
>>>>> should
>>>>> give you extra one or two stops to work with ;-)
>>>>>
>>>>> C.H.Ling
>> -- 
>> _________________________________________________________________
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>>
> 
-- 
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