Purpose of shutter on digital camera?

Lol. Cool noise ftw!

Just to add to the arguement, but aren't Camera Phone CMOS based???

chris clements wrote in post #2639430
Since the Alpha is Sony's only DSLR to date, how else was I to interpret "Sony success shows no need for a shutter in the DSLR brands that use CCD sensors."

It means they were able to use the same type of sensor as used in DSLR's in a compact camera with no shutter or mirror
All it needed was a Konica Minolta lens mount, but it was before that aquisition.

sando wrote in post #2639590
Moppie, Fuji P&S's have 1/4000 shutter speeds. Just so you know! Which is far from 1/8000, but you know what I mean.

SLR's have shutters because they're SLR's. By definition they have shutters and mirrors. They just have. So there.

I think it was Moppie who discussed this ages ago with soemone else, saying that SLR's are dinosaur technology, which is true but doesnt mean that the technmology is rubbish. A shutter allows very fast start-up times, faster shutter speeds, faster FPS in continuous shooting and the biggie: It makes a cool noise.

1/4000th isn't that far off 1/8000th

Iv refered to SLR's as Dinosaurs several times, and its a statement I maintain
But, I also think the internal compustion engine, and a whole host of other technologies should be relegated to museums.
But then I happen to think Dinosaurs are cool, just like 60s and 70s British cars!

While I accept what is being said with regard to the phsical limitiations of the technology, and I consider the SLR concept to be a very clever and effective solution to a problem, I can't help wondering if there is an alternative, but it hasn't either been thought of, or developed beyond an idea because of attitudes with in the photography world?

If it ain't broke don't fix it, dosn't mean we can't improve it

Moppie wrote in post #2639693
While I accept what is being said with regard to the phsical limitiations of the technology, and I consider the SLR concept to be a very clever and effective solution to a problem, I can't help wondering if there is an alternative, but it hasn't either been thought of, or developed beyond an idea because of attitudes with in the photography world?

If it ain't broke don't fix it, dosn't mean we can't improve it

DSLR technology is being improved all the time.

I'd be very surprised if the R&D boffins in several of the camera companies haven't been looking at developing technology that delivers the performance of shutter based DSLRs without the need for moving parts.

Remember the wheel is prehistoric technology and it still works!

Yeap and we went from burning our meats to nuking our meats!!! So someday we won't need wheels and we would be able to fly!!!

Moppie, that's my exact thoughts on it, great example with the internal combustion engine. I agree... if it aint broke, dont fix it but try to improve it, which is what is done constantly.

ScottE wrote in post #2639658
IF noise was the important factor, wouldn't it be more effective to leave out the mechanical shutter and put in a Dolby sound system that sounds like a real shutter?

I'm not an EE, but I imagine it is easier or more accurate to measure all the light reaching each sensor site for the brief time the shutter is open than to coordinate the measurement of light reaching all the sensors for the same period of time. This may result in a cleaner image with less noise.

I like your Dolby sound system idea!! This would be 7.1, I presume.

On the question about shutters on P&S cameras whether they use mechanical or electronic shutters, the answer is YES. Well, OK, I ought to clarify this, I suppose. It was mentioned that you can view an image in not-quite-real time on the LCD display so how does that jibe with having a mechanical shutter. The answer is that the mechanical shutter is open while viewing the image on the LCD and the sensor is being refreshed at some periodic rate. When the shutter button is pressed, the mechanical shutter closes at the desired shutter speed following the previous refresh. That may not be the way that all P&S cameras work, but some of them work like that anyway.

This sounds like a pretty good idea, so why don't DSLR cameras use it also. The answer is that the P&S cameras make some sacrifices in picture quality for this convenience. In one of my previous posts, I mentioned an analogy to a rain gauge for each light sensor. Although not everyone thought that this analogy held water, the actual term is well overflow and it is a phenomenon where a saturated detector essentially spills over onto adjacent pixels producing an effect called bloom. A sensor that is continually exposed to bright light will not be able to completely reset during a refresh cycle. This residual charge makes a pixel register an incorrect exposure level and also be more susceptible to bloom. The other related phenomenon is dark current noise. Each sensor element will have a certain amount of noise which exists even in the absence of light, but when continually exposed to light, the sensor temperature increases which also increases the dark current noise.

There are supercooled sensors which dramatically reduce noise, but these are for specialized scientific use and not practical in any any imaginable way for photographers. I imagine that these technical issues will be greatly improved some day, but the question then would be -- will it be as good as using the improved sensor in conjunction with the mechanical shutter system? I bet that the classical SLR shutter system will be around for a while yet.

Awsome answer Bill, thanks very much

Looks like I will have to be happy with my classic camera design, now all I need is the classic car to go with it.

My understanding is that a P&S sensor really acts like a video cam, taking multiple frames per second, but each is a distinct frame (which is why most can give you video as well). This contributes to the shutter lag that causes me to find P&S cameras completely frustrating - partly you're waiting for the camera to initiate a new frame. It's also why the rear LCD doesn't show a smooth flowing image while you move the camera.

With the SLR the sensor can be powered, but not initiate a "frame" until the exact moment (give or take a few milliseconds) when you press the shutter release, providing a precise exposure to the shutter at the moment you're wanting it.

I'm pretty sure about the first part, but the second is my extrapolation.

Greg

Compacts to work much like a video camera, taking multiple frames and feeding them to the LCD.
But, they only do so at a low resolution, basically they only use a small number of the sensors total pixel count, usually its 640x480, or what ever the video resolution is.
Then when the exposure is taken the rest of the sensor is powered up for the duration of the exposure, then shut back down again to low resolution live preview mode.

As Bill mentioned some cameras do this with the sensor covered by a shutter, usually the aperture shuts all the way, although is often easy to think this is happening, when its really just stopping down to take the photo.

sWampy wrote in post #2639073
Sorry but as an EE with a masters in computer science, this holds as much water as the theory that the earth is flat.

Well, what's your explanation? I don't have it - I flunked out of EE.

this is quite an interesting thread. the reason for the shutter in the film days was to prevent light from hitting the film when you didnt want it to. what if the real purpose of the shutter is to further protect the sensor, not from light, but from dust?

please correct me if im wrong, and if i am wrong ... spank me! thank you m'lord, may i have another? !

roeddel wrote in post #2640810
please correct me if im wrong, and if i am wrong ... spank me! thank you m'lord, may i have another? !

Ok, who gave you permission to think outside the box?

I think we can close this thread now, and I shall retract all my previous statements.


:p

thank you m'lord, may i have another? LOL!

roeddel wrote in post #2640862
thank you m'lord, may i have another? LOL!

yes baldrick, you may.

*SMACK*