[PLUG-TALK] Art Institute of Chicago exhibit

Michael Rasmussen mikeraz at patch.com
Wed Jun 29 00:15:45 UTC 2005


Jeme A Brelin wrote:
> >[1] Is it possible to do interesting long-exposure stuff with digital
> >   cameras?  Or do the stupid embedded computers and their
> >   programmers get in your way?
> 
> I'm pretty sure you can't do it.  Long exposure is an analog thing where 
> intensity of light "builds up" on the film over time.  Sensors in cameras 
> check instantaneous voltages.  You could fake it, but you may as well just 
> take thousands of little pictures and add the light intensity at each 
> pixel point over time.

The problem isn't with the stupid embedded computers and programmers.  The 
problem is keeping the chip cool.  After an extended period of exposure there
is heat buildup in the sensor chip gates that changes there properties and 
generates random volatage leaks through the gates. 

This problem is faced by astro photogrphers.  They solve it with active cooling
of the sensor chip and then doing a rack and stack of multiple exposures.  They
tend to also do seperate gamma and RGB exposure runs.  

Jeme, it's not that the camera sensors check instataneous voltages, they actually 
sum up the energy of photos hitting the sensors over time.  There  is no "instantaneous
voltage", there is a current measured over time with the current equating to a
level of photos striking the cells.


-- 
    Michael Rasmussen, Portland Oregon  
  Be appropriate && Follow your curiosity
 http://meme.patch.com/memes/BicycleRiding
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This is clearly another case of too many mad scientists, and not enough
hunchbacks.




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