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Why does the 1D use a mechanical shutter?

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I guess that the mechanical shutter is there to prevent dust from entering the ccd during lens changing. The ccd is only exposed to the elements when the shot is fired. Cleaning a CCD or CMOS is quite a delicate job so minimising dust ingression is of prime importance, especially on interchangable lens cameras

Skyline
Erik Magnuson said:
Yuval Meron said:
So a mechanical shutter is required after all to prevent the
captured photo from being degraded?

Note Erik Magnuson in this thread indicated the 1D doesn't use the
mechanical shutter - just for Bulb exposures
Click to expand...
Not that the quote does not say the shutter never fires -- just
that it's not the controlling factor in the exposure. There is not
a lot of information available on the 1D CCD, so we don't know what
requirements it has.

--
Erik
Free Windows JPEG comment editor
http://home.cfl.rr.com/maderik/edjpgcom
Click to expand...
--
Skyline
 
Skyline said:
I guess that the mechanical shutter is there to prevent dust from
entering the ccd during lens changing. The ccd is only exposed to
the elements when the shot is fired. Cleaning a CCD or CMOS is
quite a delicate job so minimising dust ingression is of prime
importance, especially on interchangable lens cameras
Click to expand...
As we've been discussing, it seems likely that the mechanical shutter is doing more than this since:

1. The mechanical shutter is used at every shot. (If there were no point in having a mechanical shutter, it could simply be left open during high speed shooting, which would reduce vibration.)

http://www.canon.com/camera-museum/tech/report/200112/report.html

2. All interline transfer CCDs, like the one in the 1D, have electronic shutters, but the ones for which we have data sheets (Sonys) indicate that a mechanical shutter should still be used in conjunction with the electronic one to eliminate smear during readout.

You can check out data sheets for some of Sony's sensors here:

http://www.sony.co.jp/~semicon/english/90203.html

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
 
Any SLR worth it's salt, including digital, uses a sliding curtain...actually a pair; one leading and one trailing. This allows them to produce the very high shutter speeds they have by sliding a narrow slot of light across the image. Cheaper consumer digicams uses leaf shutters. Leaf shutters are generally limited to 1/500th of a second or slower.

Danny
lfoxracer said:
You are getting some bad info here. The exposure on digital SLR
cameras is indeed controlled by the "electronically controlled,
mechanical shutter" Meaning the little metal blades move to expose
the chip to light for a selected amount of time to create the
exposure. Why? Shutter release lag is eliminated. When you fire
the shutter on a consumer camera, the shutter must charge
elctronically and that takes more time than it does for the
mechanical shutter to react. This delay is unacceptable in pro
applications and that is why mechanical shutters are used. The
reason that the shutter speeds of the digital SLR cameras are
higher (and synch speeds too) is because of the smaller chip size
used. This allows the curtain expose the chip quicker and give
higher flash synch speeds. When full frame chip SLR cameras come
out, the speeds be the same as 35mm SLR's

http://www.MotorImages.com
Click to expand...
 
Hmmmmm that's interesting. Does D60 do the same? I have an option for high speed shooting and still another to have the shutter opened prior to taking the photo in order to reduce vibration. Having said that, the shutter curtain should remain open in high speed shooting. If shutter mirror were to remain up then you will have a blank viewfinder throughout. Guess its a matter of money, as the sony eye view finder is CCD (which I hate) giving what the main ccd is seeing

Skyline
Ron Parr said:
Skyline said:
I guess that the mechanical shutter is there to prevent dust from
entering the ccd during lens changing. The ccd is only exposed to
the elements when the shot is fired. Cleaning a CCD or CMOS is
quite a delicate job so minimising dust ingression is of prime
importance, especially on interchangable lens cameras
Click to expand...
As we've been discussing, it seems likely that the mechanical
shutter is doing more than this since:

1. The mechanical shutter is used at every shot. (If there were
no point in having a mechanical shutter, it could simply be left
open during high speed shooting, which would reduce vibration.)

http://www.canon.com/camera-museum/tech/report/200112/report.html

2. All interline transfer CCDs, like the one in the 1D, have
electronic shutters, but the ones for which we have data sheets
(Sonys) indicate that a mechanical shutter should still be used in
conjunction with the electronic one to eliminate smear during
readout.

You can check out data sheets for some of Sony's sensors here:

http://www.sony.co.jp/~semicon/english/90203.html

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
Click to expand...
--
Skyline
 
Member said:
Any SLR worth it's salt, including digital, uses a sliding
curtain...actually a pair; one leading and one trailing. This
allows them to produce the very high shutter speeds they have by
sliding a narrow slot of light across the image. Cheaper consumer
digicams uses leaf shutters. Leaf shutters are generally limited
to 1/500th of a second or slower.
Click to expand...
My Olympus 2100's Leaf shutter could expose up to 1/1,150 sec, and of course sync with the flash at this speed.
 
Skyline said:
Hmmmmm that's interesting. Does D60 do the same? I have an option
for high speed shooting and still another to have the shutter
opened prior to taking the photo in order to reduce vibration.
Having said that, the shutter curtain should remain open in high
speed shooting. If shutter mirror were to remain up then you will
have a blank viewfinder throughout. Guess its a matter of money,
as the sony eye view finder is CCD (which I hate) giving what the
main ccd is seeing
Click to expand...
Are you sure you aren't confusing mirror lockup with opening the shutter? My understanding that was that you could lockup the mirror on the D60 to reduce mirror slap, but that this did not imply that the shutter was also open.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
 
You are right, I just tried it now... It only locks the mirror up but not the shutter curtain! I thought shutter curtain does not control exposure, and that this was controlled by energizing and deenergising the CMOS.
Ron Parr said:
Skyline said:
Hmmmmm that's interesting. Does D60 do the same? I have an option
for high speed shooting and still another to have the shutter
opened prior to taking the photo in order to reduce vibration.
Having said that, the shutter curtain should remain open in high
speed shooting. If shutter mirror were to remain up then you will
have a blank viewfinder throughout. Guess its a matter of money,
as the sony eye view finder is CCD (which I hate) giving what the
main ccd is seeing
Click to expand...
Are you sure you aren't confusing mirror lockup with opening the
shutter? My understanding that was that you could lockup the
mirror on the D60 to reduce mirror slap, but that this did not
imply that the shutter was also open.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
Click to expand...
--
Skyline
 
Skyline said:
You are right, I just tried it now... It only locks the mirror up
but not the shutter curtain! I thought shutter curtain does not
control exposure, and that this was controlled by energizing and
deenergising the CMOS.
Click to expand...
Well, that's probably the main factor in controlling exposure, but it appears that having the sensor covered during readout can prevent smear - with at least some sensors. We don't know for sure about the 1D or even the D60.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
 
You're right again! Smear is really marked on CCD and less on CMOS. I had a sony F707 and the viewfinde was all smeared up, yet the photos came out OK. A point worth noting is that an exposed CCd or CMOS heats up if it is exposed. This leads to noise and hot pixels. A few degrees of temperature increase leads to double hot pixels! Astronomy ccds are cooled down to about -30 deg cel in order to reduce noise. Was thinking of putting mine in the freezer for a couple of days!!!
Ron Parr said:
Skyline said:
You are right, I just tried it now... It only locks the mirror up
but not the shutter curtain! I thought shutter curtain does not
control exposure, and that this was controlled by energizing and
deenergising the CMOS.
Click to expand...
Well, that's probably the main factor in controlling exposure, but
it appears that having the sensor covered during readout can
prevent smear - with at least some sensors. We don't know for sure
about the 1D or even the D60.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
Click to expand...
--
Skyline
 
Ron Parr said:
Shervin said:
The 1D uses a mechanical shutter for long exposeures only.
Otherwise it is not used!
Click to expand...
The shutter is "used" on every 1D exposure:

http://www.canon.com/camera-museum/tech/report/200112/report.html#t3

The only question is whether the fact that it's closed during
readout helps reduce smear.
Click to expand...
Ron, if you read that link that you posted closely, it would appear that the shutter is not really involved in the taking of a picture on the 1D in most cases. Here is the quote from your link:

"...All shutter speeds, from 30 sec. to 1/16,000 seconds are controlled by electronic charge accumulation ON/OFF switching of the image sensor (the focal-plane shutter is fully opened immediately before the electric charge accumulation and closed immediately after completion at maximum speed of 1/125 sec.). The focal-plane shutter covers and protects the CCD sensor during standby, and controls the length of bulb exposures."

It would appear that the focal plane shutter is only moving up to 1/125 sec so it can't really have an impact on images taken at speeds faster than that. Although, I suppose it all depends on how you defined "the shutter is used" in your message :)

My take on this is that the focal plane shutter is indeed used but doesn't really have an impact on the image, smearing or otherwise at speeds above 1/125 sec. If it really helped with smearing during readout, wouldn't they have drastically increased the focal plane shutter performance?

Mark

--
Truly great madness cannot be achieved without significant intelligence.
Henrik Tikkanen
 
Dr_ML said:
My take on this is that the focal plane shutter is indeed used but
doesn't really have an impact on the image, smearing or otherwise
at speeds above 1/125 sec. If it really helped with smearing during
readout, wouldn't they have drastically increased the focal plane
shutter performance?
Click to expand...
The readout speed can be an order of magnitude or two slower than the electronic shutter speed, so it can still be useful to cover the CCD during readout even if the mechanical shutter is open longer than the electronic one.

So, what you're saying is that you think there's no problem in having the CCD exposed to light while this is happening, i.e., no charge will spill over from photosensitive areas of the chip and no photons will manage to penetrate the shielding protecting the charge transfer areas. This could all be true, but it would imply a level of shielding that goes beyond what I've been able to find documented in current consumer/digital SLR sensors. Note the smear specifications on Sony's new interline transfer sensor (likely intended for the Nikon D100):

http://www.dpreview.com/news/0202/02021602sonyicx413.asp

(Note that interline transfer implies electronic shutter capability, but in this case does not obviate the mechanical shutter.)

So, I'm not ruling out that Canon designed a sensor with a level of shielding that is so much greater than what we've seen documented from others, but I'm not yet convinced either. I would be interested in seeing specifications for sensors other than Sony sensors to see if this is a peculiarity of Sony's technique, or if the extra space consumed by the shielding isn't worth the benefit.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
 
Isn't it safe to assume the exposure in D30/D60 is controlled by the mechanical shuter only - otherwise why implement a mechanical shutter capable of 1/4000 top speed, using two curtains moving slit? You could do with a slower mechanism (leaf) if exposure was actually electronically controlled by "energizing and deenergising the CMOS"
Member said:
Skyline wrote:
Click to expand...
I thought shutter curtain does not control exposure, and that this was controlled by energizing and deenergising the CMOS.
Ron Parr said:
Well, that's probably the main factor in controlling exposure, but
it appears that having the sensor covered during readout can
prevent smear - with at least some sensors. We don't know for sure
about the 1D or even the D60.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
Click to expand...
 
There is no way the 1D is limited to 1/125th shutter speed (unless I'm misinterpreting what you are saying.) Even the cheapest EOS Rebel has dual leading and trailing curtains. This is not a feature that would not be on a 1D.

Danny
Erik Magnuson said:
Daniel Lauring said:
allows them to produce the very high shutter speeds they have by
sliding a narrow slot of light across the image.
Click to expand...
But this does not apply for the 1D. The info Ron found indicates
that its mechanical shutter is limited to no more than 1/125
precisely to avoid using a sliding slit for exposure.

--
Erik
Free Windows JPEG comment editor
http://home.cfl.rr.com/maderik/edjpgcom
Click to expand...
 
I recall the Nikon 9xx series could also fire at 1/800 or so with some type of simple leaf shutter. Perhaps this is possible in conjunction with the built in electronic shutters of the CCDs. Perhaps it has something to do with the smaller CCDs they use. The Oly E10 is limited to 1/640. I recall most 35mm P&S being somewhat slower...like 1/400.

Danny
Forrest said:
Forrest41926 said:
Any SLR worth it's salt, including digital, uses a sliding
curtain...actually a pair; one leading and one trailing. This
allows them to produce the very high shutter speeds they have by
sliding a narrow slot of light across the image. Cheaper consumer
digicams uses leaf shutters. Leaf shutters are generally limited
to 1/500th of a second or slower.
Click to expand...
My Olympus 2100's Leaf shutter could expose up to 1/1,150 sec, and
of course sync with the flash at this speed.
Click to expand...
 
Yuval Meron said:
Isn't it safe to assume the exposure in D30/D60 is controlled by
the mechanical shuter only - otherwise why implement a mechanical
shutter capable of 1/4000 top speed, using two curtains moving
slit? You could do with a slower mechanism (leaf) if exposure was
actually electronically controlled by "energizing and deenergising
the CMOS"
Click to expand...
I don't know. In CMOS, you always have an electronic shutter capability, but it can either be the slow "rolling shutter" kind or the fast "global shutter" kind. I see your point that if they had the fast kind on chip, they probably wouldn't need such a fancy mechanical shutter - a good point.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
 
Daniel Lauring said:
There is no way the 1D is limited to 1/125th shutter speed (unless
I'm misinterpreting what you are saying.) Even the cheapest EOS
Rebel has dual leading and trailing curtains. This is not a
feature that would not be on a 1D.
Click to expand...
Erik is saying that the mechanical shutter is limited to 1/125, which is consistent with Canon's comments on the matter:

http://www.canon.com/camera-museum/tech/report/200112/report.html

I suspect that this means the actual round trip time and not the duration of exposure or else the shutter would not be able to keep up with the 8fps shooting rate. However, it's pretty clear the mechanical shutter is slow and that, at most, it's shielding the CCD to keep it cool and possibly prevent smear during readout.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
 
So I will get to the actual point!!! I have damaged the shutter curain whilst trying to clean the CMOS. If it were a normal film camera ,all the shots would be overexposed, but the fact that i get perfect exposure with a damaged shutter made me doubt as to what extent the shutter curain is important. I have a fixation of having a clean CMOS, I even used about 3 bars of compressor pressure to do it! Yet when dust combines with moisture the cmos becomes smudged and this cannot be solved by blowing 20 bars of pressure onto the cmos. I do need a chemical and appropriate cmos cloth to clean it. I also tried to dismantle the camera, but having bought it a couple of days ago I did not want to void the guarantee.

Any info would be greatly appreciated.

thanks for your support
Ron Parr said:
Yuval Meron said:
Isn't it safe to assume the exposure in D30/D60 is controlled by
the mechanical shuter only - otherwise why implement a mechanical
shutter capable of 1/4000 top speed, using two curtains moving
slit? You could do with a slower mechanism (leaf) if exposure was
actually electronically controlled by "energizing and deenergising
the CMOS"
Click to expand...
I don't know. In CMOS, you always have an electronic shutter
capability, but it can either be the slow "rolling shutter" kind or
the fast "global shutter" kind. I see your point that if they had
the fast kind on chip, they probably wouldn't need such a fancy
mechanical shutter - a good point.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
Click to expand...
--
Skyline
 
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