A Photography forum. PhotoBanter.com

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » PhotoBanter.com forum » Digital Photography » Digital SLR Cameras
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Why do digital cameras need shutters?



 
 
Thread Tools Display Modes
  #11  
Old February 23rd 06, 03:28 AM posted to rec.photo.digital.slr-systems
external usenet poster
 
Posts: n/a
Default Why do digital cameras need shutters?

In message ,
Alan Browne wrote:

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.


For "noise reduction mode" for long exposures; yes. For normal
purposes, cameras may use blind pixel borders on the sensor. The 20D,
for example, has a vertical strip of 74 pixels wide on the left side of
the image, and a horizontal strip 12 tall on the top. The data from
these is where the JPEG engine and RAW converters get their black values
from (and they serve a s a noise sample as well). They are actually
contained in the RAW .cr2 file, and black is left with the offsets still
in them and in the exposed image (average is typically 128.2 to 128.4).

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.


1/500 sync would be great; it would reduce the ambient softness when I
use flash fill with long focal lengths.
--


John P Sheehy

  #12  
Old February 23rd 06, 04:19 AM posted to rec.photo.digital.slr-systems
external usenet poster
 
Posts: n/a
Default Why do digital cameras need shutters?

Alan Browne wrote:
Jeremy Nixon 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.


I didn't know that. Source?


You can technically have an electronic shutter with CMOS, but not without
compromise; it's a pretty standard feature of CCD sensors. A quick google
turned up:

http://www.dalsa.com/shared/content/..._Litwiller.pdf

Page 2 of that article has a pretty good description of the difference.

--
Jeremy |
  #14  
Old February 24th 06, 05:42 AM posted to rec.photo.digital.slr-systems
external usenet poster
 
Posts: n/a
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
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
NY Times: "Digital Moves to Top-Tier Cameras" Jeremy 35mm Photo Equipment 5 February 22nd 06 12:15 PM
Why digital cameras are no good Scott W Digital Photography 26 April 12th 05 10:14 AM
Price War Hits Digital Photos MrPepper11 Digital Photography 3 March 19th 05 01:32 AM
Best Price on Digital Cameras. Joe Walsh Medium Format Equipment For Sale 0 August 18th 04 09:52 AM
Which is better? digital cameras or older crappy cameras thatuse film? Michael Weinstein, M.D. In The Darkroom 13 January 24th 04 10:51 PM


All times are GMT +1. The time now is 11:06 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Copyright 2004-2021 PhotoBanter.com.
The comments are property of their posters.