Why do we still have a shutter?

[ahmadof]

maybe i'm issing something obvious, but why is there a need for a shutter in a digital SLR? can't you just turn the sensor on and off? would this not dramatically icrease "frames" per sec. and render the flash sync irrelevant? just wondering

[Blues67]

Tradition, thats the way it is, accept it.

[vvizard]

Because if we start removing things like mechanical shutters and mirrors, our SLR's will be muted, and then there's no reason in owning them over a prosumer can. If they where to remove the noise from shutter/mirror, they might as well remove the "_CLICK_" when you mount a lens, and nobody want's that :/

No seriously, there's more to it. Consumer/prosumer cameras don't have shutters. Instead they are "continously taking pictures with their image-sensor", and the photographer kind of just selects which one to store, by clicking down the "shutter-button". If you imagine each pixel in the sensor as a bucket of water, except that you replace water with light, this approach mean that the "buckets" are never really full, their content is discarded very quickly after it get there, so you get like "little water" in you bucket each time.

DSLR's with mechanical shutters really doesn't start to fill until the shutter is opened, and then they're filled until the shutter is closed again, giving you the opportunity to actually "fill the buckets" up with light, giving more color-depth than the prosumer-models.

I'm I high? Nope, I actually think in a very simplified way, you can "kind of" explain it this way. I know I read it sometime (on dpreview.com if not wrong) and I think it was explained something like this. If you start asking critical questions to this explanations, I'll just have to ask you to google it up, or try browsing the articles at dpreview, cause I have no deep technical information to back this up out of my mind. :cry:

But again, more imporant.. THX! "The audience is listening", "sound is everything", etc, etc. I'll rather pay $200 a year to replace a shutter than to live without it's sound :wink:

[ron chappel]

The sensors used in canon DSLR's are made to transfer the signals from each pixel as soon as it is exposed to light.There are a whole bunch of technical reasons why they do it this way but it is all so thay can get the best quality signal on the chip
They COULD make them so they work all the time like a shutterless digicam but obviously that's not possible yet while still retaining the extremely high image quality that DSLR's have.

I've heard some say that it's simply because CMOS sensors can't be 'allways on' while CCD's can but that's simply false.
All major DSLR's have shutters including the ones that use CCD's
and alot of webcams use CMOS and are allways on

Some day all DSLR's will probably be made without shutters and will allow screen preview plus movie mode while still giving extremely clean noise free images 8) 8) 8) 8)

[vvizard]

I hope that day never comes, though I'm fearing it will, sooner than I hope :( The first salesman ever trying to throw that last salesargument at me while in the shop demonstrating a DSLR to me... if he then say: "Did I mention it can take 60sec of 15fps movie-clips?" I'll walk out, and will _NEVER_ return ;) Screen-previews is possible today though, but it requires letting some light through the mirror, resulting in less light in your viewfinder. Much like there exist sport-cameras that don't flap it's mirror, but let light through at the expense of 1/3 aperture-stop or so. Great for panning motorsports, as you never have any "blackouts", since the mirror is always down.. Don't know if, and if so, how much it affects image-quality though.

[Jim_T]

I'm guessing it's still cheaper to use a shutter..

The electronics and components involved in the on and off timing of shots would be cheap, but building what's needed (scanning ability or whatever) into the sensor itself might be prohibitive..

Just guessing though.. :)

[perfectpixel]

perish the thought!
I like the sound the shutter makes :D And no, the fake shutter sound playbacks don't come close to serving as a substitute for the real thing.
It's almost therapeutic to hear that shutter go swish swish swish :D :D

[PhotosGuy]

I like the sound the shutter makes And no, the fake shutter sound playbacks don't come close to serving as a substitute for the real thing.

On the other hand, the "Duck Guys" would probably like to program it to quack!
:lol:

[Ikinaa]

Are you sure, a P&S, etc don't have shutters?

Here (http://www.kenrockwell.com/tech/2dig.htm) is stated :

... their electronic leaf shutters ... in the part about P/S.

so ?

[ahmadof]

, but i am also all for revolution. I understand how keeping the sensor on at all times and only selecting the frame you want doesn't measure up quality wise. I am not interested in that or in movies. I would propose to keep the sensor off until pressing the shutter, then keeping the sensor on for 1/20, 1/100, 1/1000 of a sec or whatever. Should'nt the quality remain the same and allow for infinite shutter speeds? The other reason i see ths as a revolution is that it will allow you to vary stutter speeds on the same shot in different areas. Those tricky lighting situations will become less so. no?

[Ikinaa]

Hmmm isn't the sensor like all electronic devices/chips. If it's off, it's cold, if it turns on, it warms and changes slightly behaviour, if it's on all the time, it has always the same temperature and behaviour stays the same.
I imagine a slow shutter-shot, let's say 5 secs.
You open the shutter, the ccd turns on. it's cold, it warms up during the 5 secs and changes behaviour continously, I see see herein a change of quality during the exposure... or am i wrong?

[ahmadof]

i do not have the technical knowledge to say. does anyone know the specifics of how the canon sensor works and if this is the same as all DSLR's these days?

[IanD]

I like the sound the shutter makes And no, the fake shutter sound playbacks don't come close to serving as a substitute for the real thing.

On the other hand, the "Duck Guys" would probably like to program it to quack!
:lol:
My wife's A70 makes chirping sounds when you turn it on. Think we can hack that for the 10D shutter release :lol: :lol:

[vvizard]

Are you sure, a P&S, etc don't have shutters?

Here (http://www.kenrockwell.com/tech/2dig.htm) is stated :

... their electronic leaf shutters ... in the part about P/S.

so ?

Some "might" have, but none I know about. To make a guess that I'm quite positive will be true in 99% of all P&S camera-cases at this date: If the camera has the ability to use the LCD as a viewfinder, it doesn't use a shutter. And I certainly don't know any cameras other than DSLRs (or reeeeeeally old ones) that can't use the LCD as a viewfiinder.

I might be wrong, but I'm willing to bet you money that you won't find more than a handfull digital P&S's with shutters inside.

[Tom W]

Well, there's a couple of reasons that might be valid.

One is power consumption - a constant-on sensor and LCD will drain your batteries rather quickly.

Another is exposure control - the shutter is hard to beat. Its operation is nearly perfected.

Heat - constant pixel stimulation (for lack of a better way of saying it) probably produces a little heat in the CMOS/CCD sensor. While this heat may not be of importance to typical P&S applications, it probably serves to degrade a picture when the camera is used at higher ISO settings.

The potential for sensor damage through large, wide aperture glass. I might be stretching it a bit, but I'd hate to have my sensor exposed to direct sunlight through a 200 mm f/2.8 lens for any appreciable length of time. (actually, I'd hate to do this with my little digicam as well, but at least it can be replaced for considerably less money).

[kb244]

What if the start up of the sensor cannot start up as quickly once turned off for a interval to take the shot, as opposed to a shutter flip. Also wouldnt removing the mechanical shutter, cause more power usage, also a mechanical shutter, can insure no stray light comes in during the time of metering right before the shutter release. Also consider this, if you are trying to shoot one of those sunset scenes, wouldnt it be more dangerous to have no shutter, with the sun constantly burning the sensor thru the lens, than to have a mechanical shutter that will pop up, only for the split second needed to take the shot. I dont know bout you, but I personally do not feel we've advanced far enough to remove the mechanics out of photography, it could very well be the reason why non-DSLR cameras have the "shutter lag"

[kb244]

hehe posted at the same time as Tom W ( 8:36 )

[Andy_T]

Now that may be s simplistic approach, but ...

If it wasn't necessary for top quality, then Canon most likely wouldn't build it into their 1D cameras ... :lol:

Seriously though, I think that the signal you get from a mechanical shutter is a lot 'cleaner' than from 'turning on and off' an electronic sensor.

And if that didn't convince you yet ... You also can't compare a great Single Malt Scotch made in a pot still to that American stuff they boil in their continuous stills...

Best regards,
Andy

[Tom W]

Well, that was almost simultaneous posting, Karl. :)

[Tom W]

Whoops - you beat me that time!

[vvizard]

The potential for sensor damage through large, wide aperture glass. I might be stretching it a bit, but I'd hate to have my sensor exposed to direct sunlight through a 200 mm f/2.8 lens for any appreciable length of time. (actually, I'd hate to do this with my little digicam as well, but at least it can be replaced for considerably less money).


It's a valid point. My old prosumer Minolta Dimage 7i have an explicit warning in the manual as to _NOT_ point it into the sun. It uses a 28-200 2.8-3.5 Minolta GT-lens, and no shutter/mirror in between.

[ahmadof]

as i said, I don't know the details. But, if i read you all correctly, I've conflicting issues. If the sensor is cold, it takes time to warm up. if the sensor is always on, it uses more power and heats up causing bad pictures. what is going on with the sensor currently ( is it always on behind that shutter?) Also, if you leave a CCD in the Off state in direct sunlight, does it hurt the sensor? furthemore , how can i get a click, quack, click sound javascript:emoticon(':wink:')

[Tom W]

as i said, I don't know the details. But, if i read you all correctly, I've conflicting issues. If the sensor is cold, it takes time to warm up. if the sensor is always on, it uses more power and heats up causing bad pictures. what is going on with the sensor currently ( is it always on behind that shutter?) Also, if you leave a CCD in the Off state in direct sunlight, does it hurt the sensor? furthemore , how can i get a click, quack, click sound javascript:emoticon(':wink:')

Well, I'm not sure that a sensor needs to warm up. Given that people are getting cleaner high-ISO pictures in colder weather, I'd think that cool is the way to go.

Heck, I don't know the details either - this is all an educated guess.

[Andy_T]

The potential for sensor damage through large, wide aperture glass. I might be stretching it a bit, but I'd hate to have my sensor exposed to direct sunlight through a 200 mm f/2.8 lens for any appreciable length of time.

It's a valid point. My old prosumer Minolta Dimage 7i have an explicit warning in the manual as to _NOT_ point it into the sun. It uses a 28-200 2.8-3.5 Minolta GT-lens, and no shutter/mirror in between.

I'd have more thoughts of exposing my unshielded eye to direct sunlight focused through a potent lens system than the sensor (which is made from silicium, which is quite tougher than a human eye and can be replaced for, say, 500 US$)

Just my thoughts....
Andy

[ahmadof]

and it's not so good. i have seen it with a slr user, so be careful about that.

[Ikinaa]

as i said, I don't know the details. But, if i read you all correctly, I've conflicting issues. If the sensor is cold, it takes time to warm up. if the sensor is always on, it uses more power and heats up causing bad pictures. what is going on with the sensor currently ( is it always on behind that shutter?) Also, if you leave a CCD in the Off state in direct sunlight, does it hurt the sensor? furthemore , how can i get a click, quack, click sound javascript:emoticon(':wink:')

Well, I'm not sure that a sensor needs to warm up. Given that people are getting cleaner high-ISO pictures in colder weather, I'd think that cool is the way to go.

Heck, I don't know the details either - this is all an educated guess.

sure it's not good that the heat up, I think I've read somewhere that in astro-photography, they cool them down (http://www.licha.de/AstroWeb/reviews_fullsize.php3?iRevId=24)
I think that the more hot the sensor is, the more noise you have...

[ron chappel]

By the way,the 300D can play weird shutter sounds and turn on sounds i think.The choices are in the breezbrowser 'settings' menu somewhere...i've seen them but can't use them because the my computer is not setup for sound and that doesn't even allow me to upload any...

[scottbergerphoto]

perish the thought!
I like the sound the shutter makes :D And no, the fake shutter sound playbacks don't come close to serving as a substitute for the real thing.
It's almost therapeutic to hear that shutter go swish swish swish :D :D
Absolutely! The 1D Mark II would have to be $1000 less, if it didn't have that magnificent shutter snap!
Scott

[martcol]

I hope my kids never see this thread.... :shock:

You guys just go to prove how nerdy we can get. :oops:

Oh, how we strive for perfection of the craft but just don't take away my Cher-chung! :lol:

Martin

[defordphoto]

No shutter? May the Photo Gods be still! Millions of passed on photogs just turned in their graves!

The sound of a shutter in an SLR is akin the cocking of a shotgun. Heck, half the fun of shooting these cameras is the cool shutter sound! ;) It definitely does not match the digital shutter-sound my FujiFilm S5000 makes.

[hmhm]

Actually, most digital cameras do have a form of mechanical shutter, and that includes SLRs and the mini point-n-shoots. It is possible to do an "electronic shutter" sort of deal with a CCD by clearing the CCD and then shifting out the contents of the CCD at the end of the "shutter period", but it takes non-zero time to read the contents of the CCD, and meanwhile light continues to hit the CCD and effect the results while the data is being shifted out. This can lead to odd image artifacts, an effect called "smear". The workaround for this is a mechanical shutter to block the incoming light while the CCD is being read.

If you could make a "good" electronic shutter, that would be a great win for an SLR, as it would allow you to "shutter" the entire frame all at once, unlike mechanical focal plane shutters which at fast shutter speeds expose the frame using a "moving slit" along the frame, which introduces the notion of a flash "sync speed", i.e. a maximum shutter speed that can be used with flash. The original Canon 1D had a mechanical shutter, but still had the ability to use "electronic shutter" in the CCD itself, this gave it the ability to use really fast flash sync speeds. Note that the 1D Mark II, which has a CMOS sensor, "gave back" this functionality, i.e. the sync speed isn't quite as fast as the Mark I.

Now, compact digitals don't typically have separate shutters and diaphragms like SLRs do, they use the diaphragm as the shutter itself.

At least, that's how I understand it all...
-harry

[DAMphyne]

My old Epson P&S was so quiet I couldn't tell when it took the picture.
I had to turn on the "Crrick" sound.

[Lamplight]

I don't think I could bear to part with the click*click of the shutter. My old P&S made only a little beep when it fired. It felt so...empty. :(

[theoldmoose]

Oh my...

Without getting *too* technical, there are essentially two distinct ways to build an image sensor. One has essentially connections to all the individual cells, and the other is connected as a 'bucket brigade', either horizontally along rows or vertically along columns.

You may see either of these types in both P & S and DSLRs (the D70, for instance, has both a mechanical and 'electronic' shutter modes, to support comparatively high flash sync speeds).

In either type of sensor, there are stages that the chip goes through.

Basically, the photosites (cells) are pre-charged to some set voltage level, setting a reference black level. Then, an 'integration' (exposure) time is allowed (electronically or mechanically), and the chip leaks charges by counting the photon hits in each cell. The energy in the photons 'leaks off' the charge in the cell, so at the end of the exposure time, the cell voltage is inversely proportional to the photon count (if it hits zero, you have 'blown out the highlights').

Now, you need a readout time, in which the cell charges are transferred somehow to the Analog to Digital converter (ADC). In either case, somehow the cell charge levels must be frozen, either by copying it to another cell, or at least by blocking the cell from receiving any more photons. In the case of an 'all cells wired' sensor, the individual cells are addressed in an X,Y fashion and the charges are read out to the ADC. In the case of a 'bucket brigade' sensor, the charges are actually transferred to the adjacent row/column of cells by a clocking signal, and the ones at the edge of the chip are read out to the ADC. This process is repeated until all the accumulated charges are read out. Ultimately, the ADC output is encoded into 0=black, 255=white, if 8-bit sampling is used, or white=4095 if 12-bit is used.

Either an additional exposure cycle has been overlapped with the readout, or a new one will begin immediately (P & S continuous LCD display) or will commence on the next mechanical shutter opening.

Now, the 'bucket brigade' type of cell practically demands a mechanical shutter or some other means of blackening the scene (in machine vision, we used a bright flash or strobe of light microseconds in duration during integration [to freeze the motion of the part], then leave the scene dark during readout), so that cells that are being used to carry information for their neighbors don't accumulate more photon hits, which would smear the image.

Why build 'bucket brigade' cells? They require a *lot* less chip real estate, metalization layers and connections, use less power, and are capable of better inter-cell spacing (less dead space between cells).

The state of the art is moving very fast these days, mainly due to the boom in digital cameras. Ten years ago, CCD/CMOS sensor technology was relatively static. In another year or so, we may see all the above descriptions become obsolete as new technologies are introduced.

[pradeep1]

In about 10-20 years, this thread will be posted somewhere as a funnies section of how people thought back in the day when digital photography was new. Kind of reminds me of the time when cars first came into existence and they had wooden horses attached to the sides so as to not scare the real horses the cars rode along side with. The shutter is akin to those wooden horses on the side of your new digital wonder.

The current generation of kids being born will probably never touch a film camera, much less an all mechanical one where the shutter is like a steel trap making noise. So all this will fade into distant memory. Sorry. :wink:

[quickben]

vvizard wrote :

"" Some "might" have, but none I know about. To make a guess that I'm quite positive will be true in 99% of all P&S camera-cases at this date: If the camera has the ability to use the LCD as a viewfinder, it doesn't use a shutter. And I certainly don't know any cameras other than DSLRs (or reeeeeeally old ones) that can't use the LCD as a viewfiinder.

I might be wrong, but I'm willing to bet you money that you won't find more than a handfull digital P&S's with shutters inside. ""


ALL of Canon's "A, G, S, and Pro" series P&S cameras have shutters. Also most Nikons, Minoltas and Olympus higher-end cameras have shutters. They all use a mechanical shutter in con-junction with an electronic shutter. I assume the electronic one takes over when the shutter speed gets to a certain level and can't be effectively accurate ( although my G5 shutter is active all the way to 1/2000). They just don't make that satisfying click very loudly.

[Tom W]

In about 10-20 years, this thread will be posted somewhere as a funnies section of how people thought back in the day when digital photography was new.
....
:wink:

After reading theoldmoose's explanation, I'm thinking that some of the earlier posts are already funny.

[robertwgross]

After reading the piece by theoldmoose, I see that we have some oldtimers here.

Back in the early 1970's, medical imaging was trying to go digital. We had a device called a flying spot scanner to scan X-ray films, and we had to put a static light source behind the film that contained 16 different fluorescent tubes. Once scanned, the image processing required a PDP-11 minicomputer, and the entire lab staff supporting all of this was about a dozen.

Just think, now we can shoot digitally with a handheld camera. Amazing!

---Bob Gross---

[karusel]

It's almost therapeutic to hear that shutter go swish swish swish :D :D

Oh yes, it makes you want to do it again and again and again. Very addictive. There is NO comparison to that fake electronic buzzzklaktchhhklak.

[ahmadof]

that was exactly what i needed to understand. basically, if i understand correctly, we are just waiting for the chip transfer speed to become faster than a shutter. right? we have to keep the chip from collecting more data before we get the original data off it.

[kb244]

that was exactly what i needed to understand. basically, if i understand correctly, we are just waiting for the chip transfer speed to become faster than a shutter. right? we have to keep the chip from collecting more data before we get the original data off it.

Well not only the speed of it but probally even the sentivity while still maintaining clarity. I mean it slike a TV, except the trick is letting the TV run for hours, turn it off, then try to quickly turn it back on then back off. If you notice the TV doesnt just instantly pop up, but rather has to warm into shape. This is how I think the shutter is on some degree.

[theoldmoose]

that was exactly what i needed to understand. basically, if i understand correctly, we are just waiting for the chip transfer speed to become faster than a shutter. right? we have to keep the chip from collecting more data before we get the original data off it.

I suppose. Another way to think of it is the difference between static and dynamic memory.

Static memory is potentially very high speed (currently sub-nanosecond), but requires many more components per bit in the memory array, making it more expensive, more power hungry, and less dense (per square mm of chip area). It will hold its state though, for as long as power is applied to the circuit, without any funny clocking signals required.

Dynamic memory uses only one transistor per bit, and a low-leakage capacitor to bias the junction on the transistor on or off. The charge on the capacitor needs to be 'refreshed' every so often, though, to keep the charge from leaking away and changing the state of the bit. But, dynamic memory can be built much denser, and uses a lot less power. Also, because the bits can be packed closer, the line lengths are shorter, and the speed of the memory can be boosted some (currently in the single-digit nanoseconds), which partly makes up for the slowness of the memory from all the time-consuming refreshing and row/column addressing that goes on to read out and maintain the memory state.

Each technology has its pluses and minuses, and will tend to get used in whatever application it seems to suit most. CCD and CMOS imaging arrays are examples of the 'if the shoe fits...' philosophy.

Currently, if the right support circuitry is used, a DSLR could be built that gives a continuous LCD display. But a number of folks may not care for it. For one thing, the battery usage would go way up, and you wouldn't be able to walk around and snap several hundred shots off of one battery charge, like you can now with the 10D or 300D. For another, it would require what is known as a 'pellicle' or half-silvered mirror, so that while the mirror was down, half the light would penetrate the mirror to the sensor, and half would reflect up to the viewfinder chamber, so that you could still get a 'through the lens' view. Of course, when you split the light in half, you get half the light. Not only would this make the viewfinder dim(mer), it would affect the sensitivity of the autofocus system, and the sensitivity of the live LCD display.

A couple of recent 8 MP quasi-SLR (non-removeable lens) cameras have tried to solve this by using a high-definition electronic view finder (EVF). Unfortunately, most folks that encountered the current crop of hi-def EVFs still find them wanting. They still prefer a true, optical viewfinder for critical work.

New technology at 11... :wink:

[kb244]

The other problem i've found with EVF, is that pixelation of the EVF seems noticible, where as true optical TTL is much clearer to identify. Another thing about mechanical shutters, is that it is a method tried and tested for generations. Also it would be easier for a Mfr to repair a broken mechanical shutter, than to identify why the photosytes are not "shuttering"

[Canuck]

Late entry...
I was out shooting with the 10D and one of the 3 lenses and a friend with one of the FujiFinePix S series cameras and I laughed at the dare I call it mock-shutter sound. It was really fruity. I guess on some levels there is something more satisfying with a real shutter actuation and even the KA-THUD the full frame DSLRs/35mm cameras make. The 10D makes one too but is is very much less pronounced. That took a little getting used to, but it is still an SLR. :)

[Tom W]

Late entry...
I was out shooting with the 10D and one of the 3 lenses and a friend with one of the FujiFinePix S series cameras and I laughed at the dare I call it mock-shutter sound. It was really fruity. I guess on some levels there is something more satisfying with a real shutter actuation and even the KA-THUD the full frame DSLRs/35mm cameras make. The 10D makes one too but is is very much less pronounced. That took a little getting used to, but it is still an SLR. :)

Heh Heh - my S-400 has a fake shutter sound. It sounds more like someone ripping a postage stamp in half real quick.

On the other hand, the shutter on my FT sounds like a bank vault (OK, its probably the mirror slap, but it is substantial).

[kb244]

Well just bout allt he canon powershots have programable shutter sounds, i remeber you could set it to a bird tweet. Or something even more annoying.

[Tom W]

Well just bout allt he canon powershots have programable shutter sounds, i remeber you could set it to a bird tweet. Or something even more annoying.

There isn't much that could come out of such a small speaker that wouldn't be annoying. :)

[blackviolet]

i'm suprised some of the more 'pro' p&s don't have simulated shutter shake to go with the artificial sound. then they could provide simulated mirror lockup. and why stop there, they could also simulate sensor cleaning, etc. - omg, it just popped into my head... what would it sound like if a p&s had the 8+ fps of the mk ii?!!


but then again, my wife simulates shutter lag - she seems something she wants to take, it registers, then she takes the photo.


oblio