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Why do digital cameras need shutters?



 
 
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  #1  
Old February 22nd 06, 07:25 PM posted to rec.photo.digital.slr-systems
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Default Why do digital cameras need shutters?

I hope this isn't a silly question. Is it impossible or too expensive to
turn the sensor on and off or something instead of a mechanical shutter?
Just wondering.

Steve


  #2  
Old February 22nd 06, 07:31 PM posted to rec.photo.digital.slr-systems
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Default Why do digital cameras need shutters?

"Steve" writes:

I hope this isn't a silly question. Is it impossible or too
expensive to turn the sensor on and off or something instead of a
mechanical shutter? Just wondering.


It's possible, but slow and inaccurate. It is found on some cheap
(phone) cameras.

--
Måns Rullgård

  #3  
Old February 22nd 06, 07:45 PM posted to rec.photo.digital.slr-systems
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Default Why do digital cameras need shutters?


"Måns Rullgård" wrote in message
...
"Steve" writes:

I hope this isn't a silly question. Is it impossible or too
expensive to turn the sensor on and off or something instead of a
mechanical shutter? Just wondering.


It's possible, but slow and inaccurate. It is found on some cheap
(phone) cameras.

--
Måns Rullgård


Thanks

How can it be inaccurate? Isn't there a processor clock that could time
"shutter speed"? Just wondering and stubborn, too.

Steve



  #4  
Old February 24th 06, 05:42 AM posted to rec.photo.digital.slr-systems
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Default Why do digital cameras need shutters?

In article ,
"Steve" wrote:

How can it be inaccurate? Isn't there a processor clock that could time
"shutter speed"? Just wondering and stubborn, too.


The clock would be accurate enough, but the response time of the sensor
(both on and off) might not be.

Merritt
  #5  
Old February 22nd 06, 08:57 PM posted to rec.photo.digital.slr-systems
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Default Why do digital cameras need shutters?

Måns Rullgård wrote:

"Steve" writes:

I hope this isn't a silly question. Is it impossible or too
expensive to turn the sensor on and off or something instead of a
mechanical shutter? Just wondering.


It's possible, but slow and inaccurate. It is found on some cheap
(phone) cameras.


Not quite true. The Canon EOS1D used its CCD to control exposure while
the shutter was reduced to protecting the imager and keeping dust off,
it also meant you could use a 1/500th sec flash sync.

The MkII which replaced it (and MkIIN) use a CMOS imager so it's back to
using the shutter for controlling exposure, and sadly back to 1/250th
sec flash sync.

Cheers,
Tony
--
Newcastle upon Tyne, England

(Email address is valid ... for now)
  #7  
Old February 23rd 06, 02:49 AM posted to rec.photo.digital.slr-systems
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Default Why do digital cameras need shutters?

Rich wrote:

Flash synch, 1/4000th of a second. Not a DSLR.


Yeah, SLRs without electronic shutters can do that too. That's not really
flash sync.

--
Jeremy |
  #8  
Old February 22nd 06, 08:57 PM posted to rec.photo.digital.slr-systems
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Default Why do digital cameras need shutters?

On Wed, 22 Feb 2006 13:25:30 -0500, "Steve"
wrote:

I hope this isn't a silly question. Is it impossible or too expensive to
turn the sensor on and off or something instead of a mechanical shutter?
Just wondering.

Steve


Another reason is that it protects the sensor from things like
accidental exposure to the sun, as even if the camera was off you
could accidently point it at the sun and damage teh sensor.
  #9  
Old February 23rd 06, 02:29 AM posted to rec.photo.digital.slr-systems
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Default Why do digital cameras need shutters?

Steve wrote:

I hope this isn't a silly question. Is it impossible or too expensive to
turn the sensor on and off or something instead of a mechanical shutter?
Just wondering.


In addition to the other replies I believe the camera manufacturers also
use the shutter as a black reference to measure sensor native noise.

The Nikon D70 "electronically" shutter flash syncs up to 1/500 which is
on the "closing" side of the cycle, and I think that should be standard
on all high end DSLR's.

Cheers,
Alan

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  #10  
Old February 23rd 06, 02:50 AM posted to rec.photo.digital.slr-systems
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Default Why do digital cameras need shutters?

Alan Browne wrote:

The Nikon D70 "electronically" shutter flash syncs up to 1/500 which is
on the "closing" side of the cycle, and I think that should be standard
on all high end DSLR's.


You can only do that with a CCD sensor, not with a CMOS.

--
Jeremy |
 




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