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Old Oct 24, 2005, 10:03 AM   #1
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Do dSLRs really have focal plane shutters? How about just a really fast on/off switch?

I see references to a Focal Plane Shutter in several of Steve's dSLR reviews, and I have a hard time understanding why a digital camera would need one.

Does that mean that dSLRs suffer from the same problems that film SLRs have? i.e. objects moving very quickly across the scene appear shortened if they are moving in one direction, and appear lengthened if they are moving in the other?

And if dSLRs have focal plane shutters, why is everybody worried about getting dust on the CCD when changing lenses, if the CCD is covered by the shutter?

Is it possible that, when people refer toa focal plane shutter, they are using terminology they are familiar with from their days of using film SLRs, rather than referring to an actual component of today's dSLRs?

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Old Oct 24, 2005, 3:17 PM   #2
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My old Fuji Finepix S602 had a quietelectronic shutter with max flash synch to 1/500th.

My new Canon 20D (I love it) issues a thunderous clap as the focal plan shutter opens and closes with a maximum flash synch of 1/250th.

Apparently the S602 does it's magic by "blanking out" the sensor as an effective shutter, whereas the Canon uses a mechanical shutter because it's bigsesnor can't be "blanked out" electronically.

As for longer and shorter, I have no comment.

But if my camera could make me look thinner and richer...

-- Terry


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Old Oct 24, 2005, 10:10 PM   #3
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TCav wrote:
Quote:
Do dSLRs really have focal plane shutters?
Yes, but not all

example:


http://www.digitalreview.ca/cams/CanonEOS20D.shtml
Quote:
New High Speed Shutter
The EOS 20D has a newly developed shutter with a top speed of 1/8000 sec., user-settable in 1/3 and 1/2 stop increments (in shutter speed priority AE and manual modes) and a maximum flash synchronization speed of 1/250 sec. First or second curtain flash sync is possible. The shutter's APS-C configuration allows a reduction in the size of the unit, smaller shutter blades with lower inertial mass, and shorter travel distance. Stronger magnets are used for each shutter curtain, permitting better control of the blades.
http://www.steves-digicams.com/2004_reviews/20d.html

Shutter type Electronically-controlled focal-plane shutter
Shutter speed 1/8000 sec. to 30 sec.(1/2 or 1/3 stop increments) plus Bulb
X-sync at 1/200 sec.



http://www.pcmall.com/pcmall/shop/detail~dpno~472929.asp

Shutter Type
Vertical-travel, mechanical, focal-plane shutter with all speeds electronically-controlled

Shutter Speeds
1/4000 to 30 sec. in 1/2- or 1/3-stop increments, bulb, X-Sync at 1/200 sec.

==================

This explain also why they have a slow flash sync speed, and use the same trick to High peed sync as film camera.


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Old Oct 24, 2005, 10:18 PM   #4
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In the same topic, my Kodak Retina Reflex III (vintage film 35mm reflex) does not have a focal plane shutter, instead, it uses a diagfram shutter .
The mirror "claps" to open the film plane , then stick up ,>> after you shoot, you can't see a thing anymore :G
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Old Oct 24, 2005, 10:44 PM   #5
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So, on this camera, the shutter speed will always be an even number, whereas cameras that use the electronics of the CCD to time the exposure will have exposure times of, like, 5/1143 seconds. Right?
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Old Oct 24, 2005, 10:47 PM   #6
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Yes. A friend of mine had a Kodak Retina SLR, and another friend of mine had a Kowa. Maximum shuttter speed was 1/500 and the lenses were expensive, but itwas a nice camera.
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Old Oct 24, 2005, 10:50 PM   #7
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hum... I have no idea :?
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Old Oct 26, 2005, 12:08 PM   #8
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The Nikon D70 still has a focal plane shutter but for faster speeds it uses an electronic shutter. The Nikon documentatio states that the flash sync speed is 1/500 but users have found that if you use a manual flash it syncs at any speed. There are some good examples in the Nikon Dslr forum http://www.stevesforums.com/forums/v...mp;forum_id=58
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Old Oct 26, 2005, 12:14 PM   #9
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So it's the cameras without the focal plane shutters that can get dust on the CCD, right?
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Old Oct 26, 2005, 2:31 PM   #10
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More info over at the thread, and corrects some common misconceptions:

http://forums.dpreview.com/forums/re...hread=15525267
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