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Electronic vs mech shutter with examples

Discussion in 'This or That? (MFT only)' started by Kiwi Paul, Sep 26, 2012.

  1. Kiwi Paul

    Kiwi Paul Mu-43 Top Veteran

    729
    Aug 15, 2011
    Aberdeen Scotland
    I must admit I was initially confused why an electronic shutter (G5) and a mechanical (focal plane) shutter should perform differently, after all a shutter speed is a shutter speed right??? So I did some reading and once I understood what was going on did some testing to prove what I'd just read.

    For those of you who who don't understand how a focal plane shutter works then I suggest reading this article and then do a Google search on how a CMOS sensor is used as an electronic shutter.

    The bottom line is that a mechanical shutter (focal plane) takes typically 1/250secs to move from the top to bottom of a sensor, in other words at shutters 1/250 and faster the top of the sensor is exposed 1/250secs before the bottom of the sensor, the exposure is controlled by the gap between 2 curtains that set the time any portion of the sensor is exposed.

    In the case of the G5 electronic sensor the way the data is read off the sensor results in the top of the sensor been read before the bottom of the sensor and it appears this is slower than 1/250 of the mech shutter. The exposure is set by the time period the pixels are exposed before being "read" but it still takes more than 1/250secs to read the whole sensor.

    This results in photos been smeared or distorted if the odject is too fast moving or the camera is moved too fast and the effect is waaaaay more pronounced with an electronic shutter.

    The point of all this is just make you aware of the limitations of the G5 electronic shutter, be wary when shooting fast moving objects or when panning, I use the electronic shutter and it's great as long as its used in the right conditions. You will just have to experiment to suss out where the limits fall.

    Below are samples...all 35mm, 1/250sec, I move the camera left to right as I took the photo...

    Mech shutter



    Electronic shutter


    1/2000 mech shutter


    1/2000 electronic shutter



    Paul
     
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  2. RobWatson

    RobWatson Mu-43 Hall of Famer

    I don't know exactly how the electronic shutter is implimented but it looks like it is intended to be used as part of the video process so as to work well with progressivescan video.

    A very poor way to make a general electronic shutter. I have some CCD cameras in which the electronic shutter works in such a way as to freeze motion with none of the 'distortions' seen in the previous post (even down to 1/10,000 sec). I see no reason why the same could also not be used in a progressive scan video unless the downstream signal processing simply cannot handle the datastream except sequentially (which matches very well with progressive scanning).

    Quality video cameras are not still cameras nor vice versus.
     
  3. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Dara
    Thanks for posting this comparison. Yes - this is a standard limitation of the current electronic shutter implementation. The so-called 'global shutter' does not have this problem as it reads all photosites of the sensor simultaneously.

    The flip side is that there is no shutter vibration with the electronic shutter. A number of folks have reported that lenses with the double-image problem (the Panasonic 14-42X and 45-175X for example) have far less trouble with the electronic shutter.

    DH
     
  4. Kiwi Paul

    Kiwi Paul Mu-43 Top Veteran

    729
    Aug 15, 2011
    Aberdeen Scotland
    Yep, thats what I've found too with the 45-175.
    It's a pity it's not a global shutter though.

    Paul
     
  5. jloden

    jloden Mu-43 Hall of Famer

    May 15, 2012
    Hunterdon County, NJ
    Jay
    I've played around with the electronic shutter since I got my G5 and this pretty much matches my experience. I've found it somewhat difficult to successfully shoot pictures of people or other moving objects with the electronic shutter. On the plus side the totally silent shutter is a boon for keeping people relaxed, and not just for candids/street photos. I noticed that even taking posed photos it's easier to catch people relaxed (and smiling naturally) with the electronic shutter on, which is a nice feature.

    I will continue to rely on the regular mechanical shutter the vast majority of the time, but when shooting pictures where the shutter sound would be unwelcome or even lose me a photo op, I do appreciate having the option with the G5.
     
  6. meyerweb

    meyerweb Mu-43 Hall of Famer

    Sep 5, 2011
    Note that you can get similar distortion even with focal plane shutters if the subject is moving fast enough, like a race car.

    And if modern digital cameras still used CCD sensors it might be much easier to build a "global shutter." Unfortunately, CCD sensors have significant other limitations compared to CMOS sensors. In general CMOS sensors are superior for quality photographic imaging.

    CMOS shutters read out one row at a time, which is why you see this distortion. A moving image is at a different position on the lower row as compared to a higher row when read.

    It would seem building a global readout CMOS sensor is proving to be very, very difficult, since I'm not aware of any manufacturer that has a commercially available camera equipped with one.
     
  7. phrenic

    phrenic Mu-43 All-Pro

    Sep 13, 2010
    Thanks for the comparison. Definitely worth keeping in mind.

    And that's a great reason to have it as an option to toggle on and off. For moving fast moving objects and pans, mechanical is the way to go, but I think I like the silence and reduced vibration on most of the time and will probably keep the electronic shutter on by default.
     
  8. RobWatson

    RobWatson Mu-43 Hall of Famer

    I'll not debate CCD vs. CMOS.

    CMOS has amplifier and readout on every pixel so there is no reason one cannot impliment a global shutter on CMOS. CMOS shutters do not have to read out as you describe. Generally speaking CMOS is much more flexible compared to CCD in many areas and it is shame to see so little creative deployment in this respect. APS (active pixel sensor) style implimentation does have global (and other) shutter modes.

    Having hardware with appropriate bandwidth to manage the possible datastreams from CMOS are not so redily available in consumer (or pro) grade cameras (as opposed to specialty scientific grade cameras). The sequential read modes (ala progressive scan) that are used are actually a bottleneck i nthe datastream. CMOS can simultaneously dump all pixels - that is a lot of data.

    Frame transfer CCD might have decent global shutter potential (still significant problems here). Interline transfer CCD certainly has global shutter action. Full frame CCD is going to be limited to mechanical shutters.


    FYI These guys off both global and rolling shutter action in CMOS.
     
  9. heedpantsnow

    heedpantsnow Mu-43 Veteran

    332
    Jul 24, 2011
    So which cameras have which kind of shutter? Or is the electronic shutter a common feature that you simple "turn on/off" when you don't want to use the mechanical shutter?
     
  10. gcogger

    gcogger Mu-43 Veteran

    342
    May 25, 2010
    UK
    Graeme
    The Panasonic G5 is the only micro 4/3 camera with the electronic shutter. It's an option you can turn on in the menus.