Shutter on P&S cameras

Discussion in 'Digital Discussion & Q&A' started by iskoos, Jan 18, 2010.

  1. iskoos

    iskoos TPF Noob!

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    Some say P&S cameras don't have shutter. That's not true. Or maybe they say some of them don't have it. I have seen and owned a few P&S yet never seen one without a mechanical shutter.
    The ones I currently have Canon A70 (very old) and A640 have some sort of mechanical center shutter (must be a leaf shutter).

    I observed it very closely and the shutter is normally open(due to constant live view). It stays open during the exposure but it closes after the exposure ends while the camera processing the picture. Do you know why?

    And the second question is that do you know any P&S camera that doesn't have a mechanical shutter? Like camera cell phones...
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    I think you may be mistaken. :scratch:
     
  3. iskoos

    iskoos TPF Noob!

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    Well, then correct me as moderators do:)
     
  4. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    I just checked on a Nikon P&S camera I have here, and I do see something that looks like a shutter...go figure :blushing:

    I can't tell, but if it closes after the exposure, then it can't really be a true photographic shutter. But if it closes to end the exposure, then it really is the camera's shutter.
     
  5. iskoos

    iskoos TPF Noob!

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    Yep!.. When I did this test, I was so sure that I wasn't going to see any mechanical(physical object) shutter that would close the aperture hole but I did and this surprized me. And I timed it; picked a long exposure (like 10 sec.) and counted the seconds while pointing a flashlight into the lens so I can see what's going on. At the end of the selected exposure time, bam!.. something closed the hole... Camera then took a few more seconds to finish what it was doing (live view was unavailable all this time) and then restores the live view.

    I searched the web for hours basically but couldn't find enough info about it...

    I will see if somebody chime in on this...
     
  6. Garbz

    Garbz No longer a newbie, moving up!

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    Actually MOST P&S cameras don't have a mechanical shutter. I think you may be confusing the shutter with another very important part in the camera. The key alarm bell for me rang when you said "leaf".

    You may be getting the aperture mechanism in the lens confused with the shutter. All P&S cameras have some kind of aperture mechanism in the lens, but very few have shutters. For the most part they add cost and a heck of a lot of complexity to a very simple device. Or you may not. If as you say it closes after the exposure it's likely to be a shutter mechanism.

    Now that said there are some P&S cameras that do have shutters for an important image quality reason. CCDs (or was it CMOS, I can't remember now but I think CCDs) required that the sensor data is read out in the dark. I think this was to prevent the phenomenon called blooming which has a small but noticeable affect on the image quality. You will typically find these shutters in high-end point and shoot cameras.

    I've pulled apart a few very cheap Olympus cameras over the years (we're talking sub $150) and none of them had a mechanical shutter. Can't for the life of me remember the model numbers though.
     
  7. iskoos

    iskoos TPF Noob!

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    Thank you Garbz for taking time to reply. I would say I am pretty sure I am not confusing the aperture mechanism with what I think may be the shutter leaf. I can clearly see the aperture mechanism in the very back of the lens when I look up closely. Especially when the lens zooms in, it is much easier to see due to the magnification. It opens up and closes in circular motion just like an iris of a human eye. The other leaf (which I think might be the shutter but probably is not) that I am talking about closes in front of it. It is very fast and hard to follow. But it feels it starts from one side and goes all the way to other side (like a curtain) till it closes the lens opening etirely.
    Take a P&S camera and see it for yourself. I am pretty sure Mike did see the same thing on his Nikon P&S!..
    That is NOT the aperture mechanism!..

    On the other hand what you said in your 3rd paragraph makes sense. It could be the very reason why this mechanical part closes the lens opening after the exposure taking. If the sensor data needs to be read out in total darkness, there I have the answer why that piece closes the lens opening. But again the lens gets closed with something other than the aperture mechanism. I am sure of it. It is NOT the aperture mechanism that closes the lens. At least in my Canon P&S cameras...
     
    Last edited: Jan 19, 2010
  8. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    I also thought, at first, that there might be some confusion with the aperture blades...but no, I'm seeing an actual curtain travel vertically and close up the lens, in front of the aperture blades...but only after the exposure.

    Maybe it does have to do with CCD sensor needing dark as the date is pulled off the sensor. :scratch: (I don't know which, but it would make sense the it's CCD, not CMOS)
     
  9. iskoos

    iskoos TPF Noob!

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    Both of my Canon P&S cameras have CCD in them. So I guess I found the answer to my question in this thread. If CCD needs darkness to process the data, that cutain just does that.
    This is the reason why I love internet forums so much...:)
     
  10. Garbz

    Garbz No longer a newbie, moving up!

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    Needs, no. There are image improvements especially in high contrast situations to having a dark readout, but a CCD does not strictly need a shutter.

    Also "take a P&S and see for yourself" is a misnomer. As I mentioned before many of them have very different designs. The camera which I ripped to pieces was an Olympus C310Z that definitely had no shutter since after I failed with the IR conversion I decided to completely! dismantle it and count the number of components. Surprisingly simple device. On the flip side, my dad's Olympus C-730 bought about 5 months earlier but a higher quality camera does have a mechanical shutter which reacts just as you describe (closes for readout).
     
  11. iskoos

    iskoos TPF Noob!

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    Himmm... You confused me a bit with your above comment to be honest. First of what is "Needs, no."? I didn't understand what you were refering to with that.

    Second, why is it misnomer to say "take a P&S and see for yourself"? I just wanted you to see that what I was talking about is NOT the aperture mechanism as you thought I was thinking. Based on what I have seen so far (and also Mike saw the same thing), many (means not all of them) of the P&S cameras will likely have similar mechanism. So if you had one handy, there would be a good chance that you would see that curtain. And if you wouldn't see that curtain then, you would just tell us that the one you have doesn't have that mechanism.
    And the last thing I am confused is the statement about your dad's C-730. You are saying it has a mechanical shutter just like I described. Are you calling that curtain a shutter now? Because I was convinced that what I saw wasn't a shutter mechanism. At least it wasn't something to end the exposure.
    Well, the only purpose of this post is to find out what is right and what is not. That's all I am after...
     
  12. Garbz

    Garbz No longer a newbie, moving up!

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    To clarify. What I mean is that a camera with a CCD sensor does not strictly need a shutter or mechanism that allows readout to occur in the dark. It's a nice to have feature for the image improvements but it's not critical to create a functioning camera.

    The misnomer is just that the very first camera example I gave was one which didn't have a shutter, so I can't just pick up "a" P&S camera to see what you're talking about, I'd need to pick up one with a shutter. :lol:, anyway kind of a moot point so late in the thread.

    My dad's C-730 had something as you described. In this case it looks to be behind the aperture blades. I can't tell the configuration, could be a leaf, could be a curtain, but what is certain that it is damn quick and only used for the readout at the end of the exposure. I'd call any mechanical mechanism designed to blind the sensor a shutter. Whether it is used to control the exposure, or just for readout purposes, or both, I would still call it a shutter. I can't confirm exactly if that's what you're seeing because quite simply I don't have one, but it is a common design for a shutter to be used only at the end of the exposure.

    Interestingly enough the D70 (I think, ... possibly D40?) has the both configuration. The mechanical shutter works as one would expect all the way to the sync point. Beyond the sync point though the shutter opens before the CCD is activated, the CCD exposure is then terminated, followed by the curtain closing, and readout occurring. This allows a flash to sync with the camera up to the max shutter speed, 1/4000th of a second.
     

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