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Why does the 1D use a mechanical shutter?

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Yuval Meron

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Forgive me if this is an obvious question, but I was wondering why D-SLRs use mechanical shutters instead of electronic ones.

Are mechanical shutters better in any respect than electronic ones? The 1D I understand has an electronic shutter, and so can reach 1/500 x-sync speed and 1/16000 top shutter speed. These are awesome numbers that cannot be supported by a mechanical shutter. So why does the 1D have a mechanical shutter to begin with?

Isn’t it safe to assume that future D-SLRs will have only electronic shutters – and perhaps also an onboard soundcard to imitate that orgasmic sound of the mechanical shutter firing? :)

Yuval
 
You don't need a soundcard unless you are generating sounds on the fly (that aren't pre-recorded). a fake shutter sound can be encoded into a small piece of hardware, and then just played back through a small speaker without the need for a sound card. :)

and with this, my G1 (and i am assuming the G2), has a "shutter sound" setting where you can turn on and off a fake mechanical shutter sound. :)

It sounds cheesy. :)
Yuval Meron said:
Forgive me if this is an obvious question, but I was wondering why
D-SLRs use mechanical shutters instead of electronic ones.

Are mechanical shutters better in any respect than electronic ones?
The 1D I understand has an electronic shutter, and so can reach
1/500 x-sync speed and 1/16000 top shutter speed. These are awesome
numbers that cannot be supported by a mechanical shutter. So why
does the 1D have a mechanical shutter to begin with?

Isn’t it safe to assume that future D-SLRs will have only
electronic shutters – and perhaps also an onboard soundcard
to imitate that orgasmic sound of the mechanical shutter firing? :)

Yuval
Click to expand...
 
Ron Parr said:
The 1D has an electronically controlled mechanical shutter. All
current digital cameras (except the $100 kind) have mechanical
shutters to prevent smear during readout.
Click to expand...
http://www.usa.canon.com/EOS-1D/faqs.html

Q: Were the maximum 1/16,000-second shutter speed and 1/500-second X-sync made possible by a mechanical shutter?

A: No, they were realized by an electronic shutter that changes the duration of time that electric signals are stored in the CCD sensor. The mechanical shutter employed in the EOS-1D works only when controlling the bulb exposure length, and also functions as a cover that protects the CCD sensor.

--
Erik
Free Windows JPEG comment editor
http://home.cfl.rr.com/maderik/edjpgcom
 
Yuval Meron said:
This is interesting - what do you mean by "smear during readout" ?
Click to expand...
If you've used a camera with a full-time preview LCD, you may have noticed that when you point the camera at a bright light source, the bright areas seem to bleed into the surrounding areas on the LCD. This isn't a function of the LCD, but a function of the sensor. It's called smear.

I'm not an expert on this, but I've noticed that datasheets for Sony's CCDs all indicate that you need to use a mechanical shutter to eliminate smear. Here's a page that I found which describes some sources of smear:

http://213.198.67.7/html/pdf/papers/smear_e.pdf

I can't vouch for it's accuracy, but it seems plausible and consistent with what Sony is claiming. I believe that CMOS may be more resistant to smear than CCDs, but I don't know for sure.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
 
So in essence you're saying the mechanical shutter is no more than a sensor protector, and that electronic shutters can deliver superior performance to mechanical shutters. And being electronic they must be more reliable as well. This is very interesting and indicates mechanical shutters are to be replaced by electronic ones as technology progresses.

Well then, there goes my beloved shutter sound. I guess I will have to settle for the mirror flip sound... :)
Member said:
Q: Were the maximum 1/16,000-second shutter speed and 1/500-second
X-sync made possible by a mechanical shutter?

A: No, they were realized by an electronic shutter that changes the
duration of time that electric signals are stored in the CCD
sensor. The mechanical shutter employed in the EOS-1D works only
when controlling the bulb exposure length, and also functions as a
cover that protects the CCD sensor.

--
Erik
Free Windows JPEG comment editor
http://home.cfl.rr.com/maderik/edjpgcom
Click to expand...
 
I see. But then having a mechanical shutter prevents full-time LCD preview altogether doesn't it
Ron Parr said:
Yuval Meron said:
This is interesting - what do you mean by "smear during readout" ?
Click to expand...
If you've used a camera with a full-time preview LCD, you may have
noticed that when you point the camera at a bright light source,
the bright areas seem to bleed into the surrounding areas on the
LCD. This isn't a function of the LCD, but a function of the
sensor. It's called smear.

I'm not an expert on this, but I've noticed that datasheets for
Sony's CCDs all indicate that you need to use a mechanical shutter
to eliminate smear. Here's a page that I found which describes
some sources of smear:

http://213.198.67.7/html/pdf/papers/smear_e.pdf

I can't vouch for it's accuracy, but it seems plausible and
consistent with what Sony is claiming. I believe that CMOS may be
more resistant to smear than CCDs, but I don't know for sure.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
Click to expand...
 
There are other ways to achieve full-time LCD preview. Its been discussed considerably in this forum. I'm of the opinion that you can introduce another 'prism' between the shutter and the OVF to direct some of the light to a second, very small, CCD or CMOS sensor. This will allow you to have a full-time LCD preview without degrading the image quality of the captured photo.

Joo
Yuval Meron said:
Ron Parr said:
Yuval Meron said:
This is interesting - what do you mean by "smear during readout" ?
Click to expand...
If you've used a camera with a full-time preview LCD, you may have
noticed that when you point the camera at a bright light source,
the bright areas seem to bleed into the surrounding areas on the
LCD. This isn't a function of the LCD, but a function of the
sensor. It's called smear.

I'm not an expert on this, but I've noticed that datasheets for
Sony's CCDs all indicate that you need to use a mechanical shutter
to eliminate smear. Here's a page that I found which describes
some sources of smear:

http://213.198.67.7/html/pdf/papers/smear_e.pdf

I can't vouch for it's accuracy, but it seems plausible and
consistent with what Sony is claiming. I believe that CMOS may be
more resistant to smear than CCDs, but I don't know for sure.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
Click to expand...
Click to expand...
--
  • Canon EOS D-30 & PowerShot S100
  • Maybe one day I'll take a decent picture. In the meantime, I'll blame the equipment. :)
 
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
Joo said:
There are other ways to achieve full-time LCD preview. Its been
discussed considerably in this forum. I'm of the opinion that you
can introduce another 'prism' between the shutter and the OVF to
direct some of the light to a second, very small, CCD or CMOS
sensor. This will allow you to have a full-time LCD preview without
degrading the image quality of the captured photo.
Click to expand...
 
Erik Magnuson said:
Ron Parr said:
The 1D has an electronically controlled mechanical shutter. All
current digital cameras (except the $100 kind) have mechanical
shutters to prevent smear during readout.
Click to expand...
http://www.usa.canon.com/EOS-1D/faqs.html

Q: Were the maximum 1/16,000-second shutter speed and 1/500-second
X-sync made possible by a mechanical shutter?

A: No, they were realized by an electronic shutter that changes the
duration of time that electric signals are stored in the CCD
sensor. The mechanical shutter employed in the EOS-1D works only
when controlling the bulb exposure length, and also functions as a
cover that protects the CCD sensor.
Click to expand...
As I mentioned in a response above, all of Sony's CCDs, even the one rumored to be in the new Nikon D100, need a mechanical shutter to reduce smear during readout despite having electronic shutter capability on chip.

It's not clear if Canon is merely emphasizing the role of the electronic shutter in their design or if they're saying that they really put enough light shielding in the charge transfer area to do this completely electronically. Since readout time is much longer than esposure time, the mechanical shutter can still help reduce smear even if it's slower than the electronic one.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
 
vtrac said:
and with this, my G1 (and i am assuming the G2), has a "shutter
sound" setting where you can turn on and off a fake mechanical
shutter sound. :)
Click to expand...
makes that stupid sound also(my wife has one). Luckily you can turn it off.

-John
 
Ron Parr said:
It's not clear if Canon is merely emphasizing the role of the
electronic shutter in their design or if they're saying that they
really put enough light shielding in the charge transfer area to do
this completely electronically.
Click to expand...
The 1/50,000s max speed and 1/500s sync speed can only be obtained with using the CCD electronics as the shutter. No mechanical shutter can perform like this. (The term "electronic shutter" is badly overloaded as it's also used to indicate mechanical shutters that are electronically controlled as opposed the older type that used a clockwork like mechanism.) As the poster was asking specifically about the 1D and I had recently come across this link, I thought I'd share it.
Member said:
Since readout time is much
longer than esposure time, the mechanical shutter can still help
reduce smear even if it's slower than the electronic one.
Click to expand...
Certainly the quote from Canon only talks about "controlling the exposure". It says nothing about how the shutter fires otherwise. I suspect that the higher shutter speeds on most digital cameras result from the CCD. For one thing, I don't think you would want to expose the CCD via a moving slit like most focal plane curtain shutters do for speeds > 1/250th. If that's the case, than the mechanical shutter on the 1d may be limited to 1/250th.

If anyone wants to lend me their 1D, I'll promise to perform extensive field testing to determine exactly how it operates!

--
Erik
Free Windows JPEG comment editor
http://home.cfl.rr.com/maderik/edjpgcom
 
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
 
Erik Magnuson said:
Ron Parr said:
It's not clear if Canon is merely emphasizing the role of the
electronic shutter in their design or if they're saying that they
really put enough light shielding in the charge transfer area to do
this completely electronically.
Click to expand...
The 1/50,000s max speed and 1/500s sync speed can only be obtained
with using the CCD electronics as the shutter. No mechanical
shutter can perform like this. (The term "electronic shutter" is
Click to expand...
1/50,000???

In any case, it wasn't my intention to imply that the mechanical device was the only thing invovled in exposure. It's known that the 1D uses an interline transfer CCD, which implies an electronic shutter capability.
Member said:
badly overloaded as it's also used to indicate mechanical shutters
that are electronically controlled as opposed the older type that
used a clockwork like mechanism.) As the poster was asking
specifically about the 1D and I had recently come across this link,
I thought I'd share it.
Click to expand...
I'm glad you posted the link.
Member said:
Member said:
Since readout time is much
longer than esposure time, the mechanical shutter can still help
reduce smear even if it's slower than the electronic one.
Click to expand...
Certainly the quote from Canon only talks about "controlling the
exposure". It says nothing about how the shutter fires otherwise. I
suspect that the higher shutter speeds on most digital cameras
result from the CCD. For one thing, I don't think you would want
to expose the CCD via a moving slit like most focal plane curtain
shutters do for speeds > 1/250th. If that's the case, than the
mechanical shutter on the 1d may be limited to 1/250th.
Click to expand...
I think the exposure is indeed controlled by the CCD, except for some of the full frame Kodaks. However, I also suspect that having the shutter closed during readout is important. My understanding of CCD design, which I admit is still rather limited, suggests that it requires a good bit of shielding to get a fully electronic shutter that does not also require a mechanical shutter to prevent smear. This shiedling adds complexity and consumes space that would otherwise be used for photodetection.

Here's a link to a Sony web page that (badly) describes their efforts to reduce smear:

http://www.sony.co.jp/en/Products/SC-HP/SG/CCD/newstructure.html

It's noteworthy that even with their improvements, their interline transfer CCD still has detectable smear (-110 dB) when used without a mechanical shutter.

FWIW, Canon's CCD source is rumored to be the same as Nikon's, which is rumored to be Sony.

--
Ron Parr
FAQ: http://www.cs.duke.edu/~parr/photography/faq.html
Gallery: http://www.pbase.com/parr/
 
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
 
That is indeed a different view than what was expressed by other folks here, and it does sound convincing. However What Ron says also sounds plausible...
 
Most DSLRS use a mechanical shutter to reduce the amount of noise that is generated when a CCD or CMOS powers up. What they do is that the CMOS or CCD's data is not read until the shutter opens.

The 1D uses a mechanical shutter for long exposeures only. Otherwise it is not used!
 
Ron Parr said:
1/50,000???
Click to expand...
Sorry, typo. Only 1/16,000.
Member said:
http://www.sony.co.jp/en/Products/SC-HP/SG/CCD/newstructure.html
Click to expand...
Ooh, another good link. Nosing around that site gives this quote which kind of confirms my supposition that higher speeds are implemented with CCD shutters:

"The Sony CCD employs the world's first inter-line transfer system with a variable speed electronic shutter. The shutter speed is continuously variable from 1/60 second to 1/10000 second, making it possible to clearly photograph a fast moving object..."

( http://www.sony.co.jp/en/Products/SC-HP/SG/CCD/sensor-frame.html )

That site also has some very interesting diagrams that help shed light (pardon the pun) on the angular sensitivity issues.

--
Erik
Free Windows JPEG comment editor
http://home.cfl.rr.com/maderik/edjpgcom
 
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