How do digital cameras work?

[boobbbers]

I never thought of it until now. Many point and shoot digital cameras have removed the view finder and just use the LCD screen. My Panasonic is like that. So in order to have the live view on the LCD screen that would mean the shutter is open and the sensor is continuously capturing light! What I don't understand is exactly how the shutter works! When you capture an image on a DSLR the shutter opens and the sensor captures light, but in a point and shoot where the sensor is continuously capturing light, the shutter is open, and when you press the shutter button, its already open! Doesn't that mean the camera is not relying on an actual/physical shutter to cut off the light since it can't. The only thing I can think of is the shutter is digital/virtual, and pretty much processed in the memory.

Can anybody clear this up for me if anybody knows?

[Olivier H]

Your guess is pretty accurate.

The camera actually uses what is called "electronic shutter" which means "take the light from the sensor for x seconds and then shut if down".

[Olivier H]

By the way, if anybody can give a more accurate answer, that would be great.

[dognutmom]

I was under the impression that the point & shoots didn't actually show you the view through the shutter. The viewfinder and the live screen aren't exactly the same as what the shutter would capture. In old film point and shoot cameras, the viewfinder was slightly above the shutter and sometimes the picture would cut off people's heads and such as the camera would take a picture slightly lower than what was seen in the viewfinder ... I had a camera like that <g> ;)

So ... I don't think that the shutter actually opens until you press the shutter button.

But I could be wrong :p

[JAHphoto]

Yeah, digital cameras don't have physical shutters. You'll note that you cant hear a real shutter sound when using a point and shoot digital camera (you never, ever want to leave one pointing at the sun with the lens cap off, my dad did that, fried the sensor)
The "shutter" sound you hear on a DSLR is just the mirror going up and down.

So when a point and shoot is showing you the live view, its basically in movie mode. :p

[mattdm]

Most digital SLR cameras certainly do have physical shutters. And at least some P&S cameras do too (although as noted above the shutter is actually open most of the time).

A distinction needs to be made between a "digital shutter" (no real shutter, just wipe and read from the CCD) and an electronic shutter, because the latter term is usually used to refer to a mechanical shutter with an electronic timer.

[inkista]

I never considered this. But my google-fu is strong, and I found this discussion thread on photo.net (http://photo.net/bboard/q-and-a-fetch-msg?msg_id=00HP8O) which pretty much clarifies matters.

The physical shutter is used to help clear the sensor prior to a shot being taken, and to keep additional light afterwards from creating a "smear" on the image. It's typically open most of the time, but when you actually press the shutter button, the physical shutter closes, and the sensor's buffer/charge is cleared out so no residual image information (from the live preview) will affect the shot. Then, the shutter opens, the electronic shutter switches to "on", and the exposure is taken. Both shutters close, while the camera recycles, the physical shutter is opened again.

Ever wondered why a P&S has a shutter delay while a dSLR doesn't? :)

[hpebley3]

The "shutter" sound you hear on a DSLR is just the mirror going up and down.

It's true that P&S cameras don't have a physical shutter. But I believe DSLRs still do. You can hear them when you shoot with mirror lock up; first you can hear the mirror move out of the way, then you can hear the shutter trigger.

[mattdm]

Try this: turn your camera around and look in the lens as you hit the shutter button. If it has a physical shutter, you'll see it. My Fujifilm Finepix F31fd certainly has one.

I can also hear the little click of the shutter -- and I definitely have the fake shutter sound option turned off.

This exercise is a bit easer if your camera has has an aperture priority mode -- set the aperture to the widest (smallest number) so that you're not distracted by the aperture diaphragm stopping down.

[Jamesc359]

It's true that P&S cameras don't have a physical shutter.
My Sony Cybershot has a shutter. I can see it snap shut for a fraction of a second before it takes the photo. I can also here soft, but distinct little double click as well. I do believe it's possible that some lower end P&S might not have a shutter though.


&lt;offtopic&gt; What I've always wondered about is how a D/SLR auto focuses. I know the technical aspects of it having a small strip of photo sensitive cells (a CCD) that measure the contrast of the current image, but where do they place them in an D/SLR? I mean, they can't be behind the mirror, otherwise the camera would have to operate like a P&S. In front of the mirror everything would be out of focus. ... So where do they put them? &lt;/offtopic&gt;

[boobbbers]

Try this: turn your camera around and look in the lens as you hit the shutter button. If it has a physical shutter, you'll see it. My Fujifilm Finepix F31fd certainly has one.

I can also hear the little click of the shutter -- and I definitely have the fake shutter sound option turned off.

This exercise is a bit easer if your camera has has an aperture priority mode -- set the aperture to the widest (smallest number) so that you're not distracted by the aperture diaphragm stopping down.

I tried that a couple days ago on my panasonic lumix dmc-fx3. When looking threw the lens, the physical shutter closes when the button is pressed. Its odd because it doesn't open back up until the photo is finished and is already half way done threw preview.