Purpose of shutter on digital camera?

Why is there a shutter on a digital cameras at all? Tradition, protect sensor, have a part to wear out? For the life of me I can't think of a reason to even have one. It would seem you would just turn the sensor on when you wanted to start recording light, turn it off when you wanted to stop.

not that easy, i guess some parts of the sensor would start up faster, amongst other issues!

I always wondered that myself, and actually, for those beginner DSLR users, it would probably allow them to use a "Live preview" by simply locking the shutter up by adding an option to the camera (although that's obviously not necissary, it would only be for those who like their P&S cameras very much). I always thought that the sensor could be turned off and on whenever needed, but I guess that must not be the case.

It works well on compacts, with thier smaller sensors, and I know sony made it work with a APS-C sized CCD sensor.

But, I don't know how well it would work on a full sized CMOS sensor?

That said, Sony success shows no need for a shutter in the DSLR brands that use CCD sensors.

I think it just shows they SLR's are old technology, and the manufactors are being very reluctant to change.
What I want to know is that reluctance coming from the consumer or the manufactor?

Moppie wrote in post #2638202
It works well on compacts, with thier smaller sensors, and I know sony made it work with a APS-C sized CCD sensor.

But, I don't know how well it would work on a full sized CMOS sensor?

That said, Sony success shows no need for a shutter in the DSLR brands that use CCD sensors.

I think it just shows they SLR's are old technology, and the manufactors are being very reluctant to change.
What I want to know is that reluctance coming from the consumer or the manufactor?

DSLR's use shutters and then you conclude they are "old technology"? There is so much more then a shutter that goes into a DSLR....

The start-up time is likely governed by the warm-up time of the sensor.

When shooting at 5 frames per second, and a not-fast shutter speed, there would be no time for the sensor to shut down and start up again, and keep up with 5 fps.

One would think that if Canon could eliminate the shutter, they would save a bit on the manufacturing cost of each camera, and that saving would be added to the bottom line of profits.

They haven't found a way to do it or they would have done it.

Don't counter with the argument that it would only save pennies per camera - that amount is added to the bottom line, and with a few million cameras sold, that's a lot of extra profit. Furthermore, it would make the camera silent, a big selling feature for many photographers.

Glenn NK wrote in post #2638419
The start-up time is likely governed by the warm-up time of the sensor.

When shooting at 5 frames per second, and a not-fast shutter speed, there would be no time for the sensor to shut down and start up again, and keep up with 5 fps.

One would think that if Canon could eliminate the shutter, they would save a bit on the manufacturing cost of each camera, and that saving would be added to the bottom line of profits.

They haven't found a way to do it or they would have done it.

Don't counter with the argument that it would only save pennies per camera - that amount is added to the bottom line, and with a few million cameras sold, that's a lot of extra profit. Furthermore, it would make the camera silent, a big selling feature for many photographers.

Well the startup/shut down argument doesn't hold water, the processor just ignores data, except when the imaginarry shutter is open, if there is no shutter.

Removing the shutter would make it quiter, but the mirror would still have to be moved each time, so it wouldn't be silent.

Only valid sounding reason I've seen is so they wear out, you remove the moving parts, the bodies will last a lot longer, wouldn't sell as many of them.

I was figuring I would get an answer like the sensors get overloaded if they are exposed to light all the time, but my searches haven't turned something like that up.

Steiglitz wrote in post #2638267
DSLR's use shutters and then you conclude they are "old technology"? There is so much more then a shutter that goes into a DSLR....

When was the first SLR put into production?
They are old technology.

Glenn NK wrote in post #2638419
The start-up time is likely governed by the warm-up time of the sensor.

When shooting at 5 frames per second, and a not-fast shutter speed, there would be no time for the sensor to shut down and start up again, and keep up with 5 fps.

Aha!
Now there something that makes sense.
Of course remember that the sensor has to be cleared between each shot, thats in a very short period of time.
Also, most shutter less compacts are able to run several frames per second, basicly once the sensor is charged up, they just keep it charged up, but dump the data off of it at the end of each exposure.

I wonder then if the problem then is not getting more frames per second (thats a simple matter of faster buffers and processors) but the time it takes to power up the sensor?

But, I can't imagine the sensor is kept running at full power the whole time the camera is turned on,.
Compacts with a live preview run the sensor at low power and get a low frame rate, low resolution feed for the live preview, then goto full power when the shutter is pressed.
Fuji now have a compact that will do that, and take the photo in a fraction of the time even the best SLR can.
So shutter lag is not an issue, currently a shutter less camera has the fastest response time.

sWampy wrote in post #2638475
Well the startup/shut down argument doesn't hold water, the processor just ignores data, except when the imaginarry shutter is open, if there is no shutter.

Removing the shutter would make it quiter, but the mirror would still have to be moved each time, so it wouldn't be silent.

Only valid sounding reason I've seen is so they wear out, you remove the moving parts, the bodies will last a lot longer, wouldn't sell as many of them.

I was figuring I would get an answer like the sensors get overloaded if they are exposed to light all the time, but my searches haven't turned something like that up.

Your reasoning that camera makers use mechanical shutters in order to sell more bodies is illogical. For one thing, these makers already expect to sell lots of bodies because DSLR's are still making improvements...they realize that nobody is going to wait for the shutter to wear out to replace their camera. People will want the replacement body because of lower noise, or more resolution, or faster start up, etc.

Also, a worn shutter does not mean a new DSLR is required....a shutter can be replaced for around $250 more or less depending on the body...this is not a lot of money.

So you see, I've listed at least two reasons why one cannot think that the use of mechanical shutters is for more body sales.

There are reason why DSLR's have mechanical shutters and not software driven....but I don't know, the others on this site don't know either and you should not expect us to know, unless there are camera designers/engineers present in this forum.

Moppie wrote in post #2638512
When was the first SLR put into production?
They are old technology.



Aha!
Now there something that makes sense.
Of course remember that the sensor has to be cleared between each shot, thats in a very short period of time.
Also, most shutter less compacts are able to run several frames per second, basicly once the sensor is charged up, they just keep it charged up, but dump the data off of it at the end of each exposure.

I wonder then if the problem then is not getting more frames per second (thats a simple matter of faster buffers and processors) but the time it takes to power up the sensor?

But, I can't imagine the sensor is kept running at full power the whole time the camera is turned on,.
Compacts with a live preview run the sensor at low power and get a low frame rate, low resolution feed for the live preview, then goto full power when the shutter is pressed.
Fuji now have a compact that will do that, and take the photo in a fraction of the time even the best SLR can.
So shutter lag is not an issue, currently a shutter less camera has the fastest response time.

DSLR's are new technology. The shutter design in these bodies are old technology, albeit improved. But having said that, the existence of an old shutter design in a 5D for example does not make the 5D old technology.

Otherwise one could say that the very first SLR had a shutter button, and the 1DS Mark II has a shutter button so then therefore the 1DS Mark II is old technology.

Steiglitz wrote in post #2638520
Also, a worn shutter does not mean a new DSLR is required....a shutter can be replaced for around $250 more or less depending on the body...this is not a lot of money.

Having rapair item that costs 25% of the cost of the original item, that almost breaks after warranty is up, with a none failure rate, that is cheap for you to replace, but impossible for others to replace, might not be logical to you, but I'm sure automobile makers, computer makers, appliance makers would differ with you.

Steiglitz wrote in post #2638520
Your reasoning that camera makers use mechanical shutters in order to sell more bodies is illogical. For one thing, these makers already expect to sell lots of ...............So you see, I've listed at least two reasons why one cannot think that the use of mechanical shutters is for more body sales.

Totaly agree with you there.
There is no money making conspiracy behind it.
After all compacts digitals have been sold in the millions of units, all with out mechanical shutters, and they still continue to sell in higher and higher numbers every year.

Steiglitz wrote in post #2638520
There are reason why DSLR's have mechanical shutters and not software driven....but I don't know, the others on this site don't know either and you should not expect us to know, unless there are camera designers/engineers present in this forum.

Its nice to speculate about such things, and there are some people here who are engineers, amature or otherwise, who Im sure must have some kind of a well educated reason for it.

Personaly, I think its simple a lack of will, either on the manufactors behalf, to develop a shutterless SLR (you would still need a mirror, so they might be thinking whats the point), or the consumers lack of will to accept something that differs from the long accepted norm.
If there is one thing I have noted from reading camera forums, its that SLR owners are often very stubburn and set in thier ways. A large enough number are resistant to change that the manufators might be scared to force it upon them.
You only have to look at the resistnace to digital that took 10 years for most photographers to deal with, and still exists in the minds of a number of people.
Or, the comments around this forum about the use of live preview on non-SLR cameras.
Even the amount of comments regarding Sigma lenses lately shows a strong resistance to try something new or different.

Steiglitz wrote in post #2638553
DSLR's are new technology.

The basic concept behind an SLR has not changed.
All they have done is replace the chemical sensor with a fixed digital one, and put faster and better electronic controllers in charge of things like focus and exposure.

But the basic concept has not changed, and is still universal even between different manufactors.

The only ones have tried something a little different have been Oylmpus with the E300 and E330, that used live preview by locking up the mirror and shutter at the switch of a button.
They are very nice, easy cameras to use, sadly they lack some of the image quality and feature sets avliable on conventional SLRs from Canon, Nikon and Fuji.

Remember, all the fast-response P&S cameras you're talking about have very small CCD sensors. This means at least one very important thing - there's much less distance for the electrons to travel in "reading" the sensor. There's a secondary factor in the difference between how CCD and CMOS sensors are read. IIRC, CCDs are read "row at a time" gulps, while CMOS are read in "pixel-by-pixel" sips. Between those, controlling the light influx to the CMOS almost requires a mechanical shutter if you hope to take advantage of the other pluses of CMOS. Remember, the 1D and several Nikons, with CCD sensors, have flash sync not limited by the mechanical shutter speed, suggesting that where the light can be controlled well enough that a mechanical shutter's not necessary. But with flash, there's typically a marked difference between ambient light and the flash light levels.

Jon wrote in post #2638695
Remember, the 1D and several Nikons, with CCD sensors, have flash sync not limited by the mechanical shutter speed, suggesting that where the light can be controlled well enough that a mechanical shutter's not necessary. But with flash, there's typically a marked difference between ambient light and the flash light levels.

Interesting, would certianly show a difference between use in CCD and CMOS cameras.

I also remember another thread on the topic of live preview, where the differences in CMOS and CCD showed the difficulty in useing CMOS for effective live preview.

So thats theres a valid excuse for Canon, now what about the other manufactors?