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Very strange effect by Tokina TV Lens 25mm f1.4 on Pentax-Q
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PostPosted: Tue Jan 08, 2013 2:59 pm    Post subject: Very strange effect by Tokina TV Lens 25mm f1.4 on Pentax-Q Reply with quote

I was sitting on a bus one day travelling at a speed of 100kmh. I took a picture of a building through the front window and noticed that the building was somehow "twisted"! Then I continue with that series of pictures! Anyone know why it is so? I have tried the same method with my Canon 50D but cannot reproduce the same effect! WHY?????







PostPosted: Tue Jan 08, 2013 3:11 pm    Post subject: Reply with quote

I don't know why the pictures turned out like that,

but scrolling down those pictures makes my stomach twist like those buildings do Laughing


PostPosted: Tue Jan 08, 2013 3:15 pm    Post subject: Reply with quote

Rolling shutter effect.


PostPosted: Tue Jan 08, 2013 3:28 pm    Post subject: Reply with quote

Fabian wrote:
Rolling shutter effect.


+1, rolling shutter: probably you don't notice it on your canon because of sensor size difference.


PostPosted: Tue Jan 08, 2013 3:33 pm    Post subject: Reply with quote

Definitely vertical focal plane rolling shutter effect like on the old Graflex !
This doesn't happen on 35mm slr's even with vertical shutter like the Copal.

And does this camera even have a shutter ?
I suspect it has something to do with the rate and sequence the thing saves images from the sensor. I think it may be a purely digital effect. It would be interesting to test different "shutter speeds".


PostPosted: Tue Jan 08, 2013 3:47 pm    Post subject: Reply with quote

luisalegria wrote:
Definitely vertical focal plane rolling shutter effect like on the old Graflex !
This doesn't happen on 35mm slr's even with vertical shutter like the Copal.

And does this camera even have a shutter ?
I suspect it has something to do with the rate and sequence the thing saves images from the sensor. I think it may be a purely digital effect. It would be interesting to test different "shutter speeds".


For the little I know it's completely digital and it has something to do with how cmos sensors record the image data: it's not recorded all at the same time, but there's some lag between the first and the last pixel captured. This effect has become quite known for video shooters since cmos-sensored dslrs developed video capabilities and become used at various levels, and it didn't happen when all the camcorders had good old ccd sensors.
I never tested how shutter speed affects that, it could be interesting. Now there are some video tools to correct that (in video footage it is often a PITA), but when I see it I always think of (probably spelled wrong) Zbigniew Rybcznski's "Fourth Dimension" ( http://vimeo.com/24476973 ) that plays with displacement over time.


PostPosted: Tue Jan 08, 2013 3:47 pm    Post subject: Reply with quote

luisalegria wrote:
And does this camera even have a shutter ?
I suspect it has something to do with the rate and sequence the thing saves images from the sensor. I think it may be a purely digital effect. It would be interesting to test different "shutter speeds".


Quote:
Essentially every video capable digital SLR/CSC currently on the market exhibits some level of motion-related distortion called rolling shutter artifacts. These are caused because the image data is captured and then read off the chip sequentially by rows, rather than each frame's data being captured all at once. In the case of the Pentax Q, this means that image data for the last row of a given frame is captured and read out as much as 1/30th second after the data for the top row was captured. The effect on moving objects is like that of a focal plane shutter in an SLR, but more pronounced, because the video frame is read out much more slowly than the slit of a focal plane shutter moves across the sensor.

For a camera that scans video frames vertically (as all do that we're aware of), rolling shutter artifacts will be most noticeable for subjects that are moving rapidly side to side, or when the camera itself is being panned horizontally. Verticals in the scene will appear tilted to the right or left, depending on the direction of camera motion. As an example, consider the case of a camera being panned from left to right, with a flagpole or other vertical object in the middle of the scene when recording for a particular frame begins: If the top of the object was centered horizontally when the first line of the video frame is acquired, by the time the last line of the frame has been captured, the bottom of the object will have shifted to somewhere left of center: As a result, the vertical object would appear to be leaning to the right.


Last edited by Fabian on Tue Jan 08, 2013 3:51 pm; edited 1 time in total


PostPosted: Tue Jan 08, 2013 3:49 pm    Post subject: Reply with quote

luisalegria wrote:
Definitely vertical focal plane rolling shutter effect like on the old Graflex !
This doesn't happen on 35mm slr's even with vertical shutter like the Copal.

And does this camera even have a shutter ?
I suspect it has something to do with the rate and sequence the thing saves images from the sensor. I think it may be a purely digital effect. It would be interesting to test different "shutter speeds".


Pentax_Q has no shutter in front of the sensor as far as I am aware! What's rolling shutter effect by the way? I am no photograhy expert and I would like to learn more on this forum. Thanks in advance! Smile


PostPosted: Tue Jan 08, 2013 3:58 pm    Post subject: Reply with quote

Quote:
Essentially every video capable digital SLR/CSC currently on the market exhibits some level of motion-related distortion called rolling shutter artifacts. These are caused because the image data is captured and then read off the chip sequentially by rows, rather than each frame's data being captured all at once. In the case of the Pentax Q, this means that image data for the last row of a given frame is captured and read out as much as 1/30th second after the data for the top row was captured. The effect on moving objects is like that of a focal plane shutter in an SLR, but more pronounced, because the video frame is read out much more slowly than the slit of a focal plane shutter moves across the sensor.

For a camera that scans video frames vertically (as all do that we're aware of), rolling shutter artifacts will be most noticeable for subjects that are moving rapidly side to side, or when the camera itself is being panned horizontally. Verticals in the scene will appear tilted to the right or left, depending on the direction of camera motion. As an example, consider the case of a camera being panned from left to right, with a flagpole or other vertical object in the middle of the scene when recording for a particular frame begins: If the top of the object was centered horizontally when the first line of the video frame is acquired, by the time the last line of the frame has been captured, the bottom of the object will have shifted to somewhere left of center: As a result, the vertical object would appear to be leaning to the right.


Interested piece of information! Many thanks!


PostPosted: Tue Jan 08, 2013 6:17 pm    Post subject: Reply with quote

You should untag the 'Disable BBCode in this post' when replying with a quote, enabling it makes it a pain to read quotes.


PostPosted: Tue Jan 08, 2013 6:22 pm    Post subject: Reply with quote

There I fixed it Smile


PostPosted: Wed Jan 09, 2013 12:21 am    Post subject: Reply with quote

That brings back memories from the 80's

Although very tedious to make with film using a slit scanning technique, it now comes as an After Effects tutorial.


Aanything wrote:
Zbigniew Rybcznski's "Fourth Dimension" ( http://vimeo.com/24476973 ) that plays with displacement over time.