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In the picture below you can see that the rolling shutter moves downwards...i.e., it exposes the light to the sensor from top to bottom.

.enter image description here

So the information that the sensor recieves is a bit earlier at the top of the sensor and at the bottom it is a bit late..

But the image is flipped(inverted) by the time it reaches the sensor...

so the sensor recieves lower part of the image earlier than the upper part..

But in this image below...as you can see the shadow of the cork appears even before the cork had come out ...this means that the upper part of the image reached earlier than the lower part....how is this possible..??

I'm new here...I'm really sorry if i went wrong anywhere....I hope you answer my question...

enter image description here

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    \$\begingroup\$ Is your shutter demo definitely for the camera in use? do you know whether the camera was mounted "upside down" when the photo was taken? or even sideways? Need more info. \$\endgroup\$
    – Carl Witthoft
    Jul 12, 2016 at 11:37
  • \$\begingroup\$ Yup....the camera in use is the same one...and it is perfectly upright \$\endgroup\$
    – Knight
    Jul 12, 2016 at 11:45
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    \$\begingroup\$ But that image wasn't created using the mechanical shutter - it is a video frame grab. \$\endgroup\$
    – Michael C
    Jul 12, 2016 at 14:37
  • \$\begingroup\$ The top of the camera is the bottom of the image. It's inverted as you can see from a View Camera. \$\endgroup\$
    – JDługosz
    Jul 12, 2016 at 21:32

3 Answers 3

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You are correct that the image is inverted as it is projected on the sensor and that the mechanical shutter reveals the bottom of the scene before the top of the scene. What you have missed is that the image (with the shadow of the cork falling on the red shirt at a later time than the the actual cork is seen flying through the air) is not a still frame taken using the mechanical shutter - it is a frame capture from a video recording.

During video recording the mechanical shutter stays open. It doesn't cycle between frames. The sensor itself is read out electronically in the opposite direction from the direction that the mechanical shutter normally moves - the sensor is read starting from the bottom of the sensor as it sits in the camera which is the top of the scene in front of the camera due to the lens' inversion. As the host in the video that your image is from explains, the photo in your question is a frame grab from a video recorded with the camera, not a still image recorded using the mechanical shutter.

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    \$\begingroup\$ Thank you Michael....this is the answer I've been waiting for...Thank you \$\endgroup\$
    – Knight
    Jul 12, 2016 at 15:37
  • \$\begingroup\$ The readout would be the same as the shutter's movement which is bottom to top in the image. If the electronic clearing or readout is used to replace one of the curtains for stills, it is necessarily the same as the mechanical shutter. If used in different mode only, there is o reason for it to be the same and it may be whatever worked best for the way the chip was made. In a hybrid shutter design like the sony alpha 6000 or the Canon 70D, it needs to match. Does it vary by camera, or is video "rolled" intentionally from the image top to bottom for effect? \$\endgroup\$
    – JDługosz
    Jul 13, 2016 at 1:40
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    \$\begingroup\$ I just experimented with my 7D without a lens. When using the Silent Shooting modes in Live View the first curtain is electronic. But the exposure is ended by moving the first curtain from open (which it already is when using the LCD screen in Live View) back up to the reset position. The second curtain never moves. So the first curtain ends the exposure by moving from the bottom to the top of the camera (top to the bottom of the inverted image) rather than by moving the second curtain from top to bottom of camera (bottom to top of image). The sensor is always read out the same direction \$\endgroup\$
    – Michael C
    Jul 13, 2016 at 2:21
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    \$\begingroup\$ To reiterate: During Live View the second curtain does not move. Ever. Neither for stills or video. The first curtain is in the open position prior to the shot so the sensor is exposed and can be used to provide the Live View image on the LCD screen. To mechanically end a still frame the first curtain is moved from open to closed by the same movement used to reset it to the top of the light box during conventional still shots. Thus the movement of the mechanical shutter curtain is from the bottom to top of the light box (top to bottom of the inverted image). \$\endgroup\$
    – Michael C
    Jul 13, 2016 at 2:32
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    \$\begingroup\$ As to the 70D, it has the same type of shutter design as most other Canon cameras. The Hybrid part of the 70D (and most later Canon EOS cameras all the way from the most humble Rebels to the 1D X Mark II) is in the way the microlenses over the pixel wells are made so that about 80% of the sensor's pixels can be used to perform Phase Detection AF with no appreciable loss in sensor efficiency. \$\endgroup\$
    – Michael C
    Jul 13, 2016 at 4:53
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Yes, you are right, the effect is opposite from what we would expect from a shutter moving downwards.

And this is because the shutter moved upwards, or, more specifically, it was the electronic shutter so nothing really moved, but the image data was being read from top to the bottom of the image (which corresponds to the bottom-to-top of the image sensor).

(and by the way, the shutter animations and cork guy still frame is from the slow mo guys video here on youtube: https://www.youtube.com/watch?v=CmjeCchGRQo)

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  • \$\begingroup\$ Even then the data was first collected as per the exposure of the sensor to the light physically...which is done by the shutter........ \$\endgroup\$
    – Knight
    Jul 12, 2016 at 13:42
  • \$\begingroup\$ So, is the image inverted by the lens? \$\endgroup\$
    – user152435
    Jul 12, 2016 at 13:59
  • \$\begingroup\$ To elaborate -- the referenced video explicitly states what the readout order of the electronic shutter is in this camera. It also points out why scientific high-speed cameras use "frame-transfer" sensors rather than rolling, or "line-transfer" sensors: it's so the entire image represents exactly the same slice of time. \$\endgroup\$
    – Carl Witthoft
    Jul 12, 2016 at 14:02
  • \$\begingroup\$ @user152435 yes, it is inverted, see: photo.stackexchange.com/questions/21495/… \$\endgroup\$
    – szulat
    Jul 12, 2016 at 14:03
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    \$\begingroup\$ i really couldn't figure out how does the above answer explain my question....could anyone help me out... \$\endgroup\$
    – Knight
    Jul 12, 2016 at 14:10
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no it is because of the view. The shadow part is visible here clearly. but bottom of cork is not visible. So it is feeling relatively shadow moves first. It is just due to the view

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    \$\begingroup\$ I'm sorry but i couldn't get what you're saying \$\endgroup\$
    – Knight
    Jul 12, 2016 at 11:10

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