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Is whole frame from a single moment?
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Richard Tobin
Jul 11, 2022, 8:45:01 AM7/11/22
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In a modern TV camera, do all the pixel values of a frame reflect the
illumination at a single moment, or are they values varying over the
time of a single frame, so that the bottom line is later than the
first?
-- Richard
illumination at a single moment, or are they values varying over the
time of a single frame, so that the bottom line is later than the
first?
-- Richard
Mark Carver
Jul 11, 2022, 9:27:10 AM7/11/22
to
Rolling shutters !
https://en.wikipedia.org/wiki/Rolling_shutter
<https://www.alliedvision.com/en/news/detail/sensor-shutter-modes-rolling-shutter-vs-global-shutter/?gclid=Cj0KCQjwlK-WBhDjARIsAO2sErROzhUf0KjWwLVoH0PYFB3UTdI-aGQ4Du2wkrax1DH8AoCGB42KR7UaAi28EALw_wcB>
Brian Gaff
Jul 12, 2022, 4:16:39 AM7/12/22
to
I always thought that semiconductor cameras were merely moving memory about
in silicon. Every chunk is a frame, and its then handled from the place it
has gone to depending on the system that is used. One assumes as you can now
get extremely fast frame rates for video cameras, that this is dictated by
how fast memory can be copied and processed.
The concept of the shutter type is a mechanical construct. I remember many
years ago watching a picture load into a zx Spectrum. The screen was divided
into three, and the first row of pixels in the first third filled in etc,
till that third was occupied, but no colour was there yet. then the second,
then the third and finally the colour. It appears that this was the way the
hardware was designed and so you were stuck with it as it was, but later on
when the machine had a second screen, you could hide the screens and
sequence the completed ones as an animation, just by switching the page of
memory you were using mapped to the screen.
Brian
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"Mark Carver" <mark....@invalid.invalid> wrote in message
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in silicon. Every chunk is a frame, and its then handled from the place it
has gone to depending on the system that is used. One assumes as you can now
get extremely fast frame rates for video cameras, that this is dictated by
how fast memory can be copied and processed.
The concept of the shutter type is a mechanical construct. I remember many
years ago watching a picture load into a zx Spectrum. The screen was divided
into three, and the first row of pixels in the first third filled in etc,
till that third was occupied, but no colour was there yet. then the second,
then the third and finally the colour. It appears that this was the way the
hardware was designed and so you were stuck with it as it was, but later on
when the machine had a second screen, you could hide the screens and
sequence the completed ones as an animation, just by switching the page of
memory you were using mapped to the screen.
Brian
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Blind user, so no pictures please
Note this Signature is meaningless.!
"Mark Carver" <mark....@invalid.invalid> wrote in message
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NY
Jul 12, 2022, 4:36:45 AM7/12/22
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"Brian Gaff" <brian...@gmail.com> wrote in message
news:tajal5$207si$1...@dont-email.me...
to its numerical value. Some sensors "freeze" the analogue value for every
pixel simultaneously, and then sequentially convert the voltages to digital
and read them out. Others convert each value as it is being output on the
data bus.
The former allows a global shutter - like an iris shutter on a film camera.
But it needs sample-and-hold technology for every pixel, or else an
analogue-to-digital converter for every pixel. The latter is a rolling
shutter - like a focal-plane shutter on a film camera. It is simpler because
you only need one ADC, but causes vertical objects to tilt if the camera is
panned horizontally past them.
I presume the effect is more noticeable with a video camera than it was with
a film camera because the "shutter" effect takes a whole frame (1/25 sec) to
pass from the top of the frame to the bottom, whereas focal plane shutters
on film cameras (eg 35 mm still) were usually around 1/125 second (you can
tell what it is because it's the shortest shutter speed at which flash can
be used).
As an aside... Most film cameras made the shutter travel in the vertical
direction because it was the shorter distance and so the shutter took less
time to travel it; some made it travel in the horizontal direction which
takes longer (so slower minimum flash-sync speed) but causes less
parallelogram distortion because you rarely pan (tilt) vertically: a slight
change in the aspect ratio is less noticeable than a tilting of vertical
lines.
news:tajal5$207si$1...@dont-email.me...
> I always thought that semiconductor cameras were merely moving memory
> about in silicon. Every chunk is a frame, and its then handled from the
> place it has gone to depending on the system that is used. One assumes as
> you can now get extremely fast frame rates for video cameras, that this is
> dictated by how fast memory can be copied and processed.
>
>
> The concept of the shutter type is a mechanical construct. I remember many
> years ago watching a picture load into a zx Spectrum. The screen was
> divided into three, and the first row of pixels in the first third filled
> in etc, till that third was occupied, but no colour was there yet. then
> the second, then the third and finally the colour. It appears that this
> was the way the hardware was designed and so you were stuck with it as it
> was, but later on when the machine had a second screen, you could hide the
> screens and sequence the completed ones as an animation, just by switching
> the page of memory you were using mapped to the screen.
It depends how the camera chip converts the analogue brightness of a pixel
> about in silicon. Every chunk is a frame, and its then handled from the
> place it has gone to depending on the system that is used. One assumes as
> you can now get extremely fast frame rates for video cameras, that this is
> dictated by how fast memory can be copied and processed.
>
>
> The concept of the shutter type is a mechanical construct. I remember many
> years ago watching a picture load into a zx Spectrum. The screen was
> divided into three, and the first row of pixels in the first third filled
> in etc, till that third was occupied, but no colour was there yet. then
> the second, then the third and finally the colour. It appears that this
> was the way the hardware was designed and so you were stuck with it as it
> was, but later on when the machine had a second screen, you could hide the
> screens and sequence the completed ones as an animation, just by switching
> the page of memory you were using mapped to the screen.
to its numerical value. Some sensors "freeze" the analogue value for every
pixel simultaneously, and then sequentially convert the voltages to digital
and read them out. Others convert each value as it is being output on the
data bus.
The former allows a global shutter - like an iris shutter on a film camera.
But it needs sample-and-hold technology for every pixel, or else an
analogue-to-digital converter for every pixel. The latter is a rolling
shutter - like a focal-plane shutter on a film camera. It is simpler because
you only need one ADC, but causes vertical objects to tilt if the camera is
panned horizontally past them.
I presume the effect is more noticeable with a video camera than it was with
a film camera because the "shutter" effect takes a whole frame (1/25 sec) to
pass from the top of the frame to the bottom, whereas focal plane shutters
on film cameras (eg 35 mm still) were usually around 1/125 second (you can
tell what it is because it's the shortest shutter speed at which flash can
be used).
As an aside... Most film cameras made the shutter travel in the vertical
direction because it was the shorter distance and so the shutter took less
time to travel it; some made it travel in the horizontal direction which
takes longer (so slower minimum flash-sync speed) but causes less
parallelogram distortion because you rarely pan (tilt) vertically: a slight
change in the aspect ratio is less noticeable than a tilting of vertical
lines.
John Williamson
Jul 12, 2022, 5:21:38 AM7/12/22
to
Semiconductor sensors can be made to either sense the entire frame, then
send it to a local memory buffer and on to the main stirage, or to scan
a row or pixel at a time, then poke the data stream directly into the
main storage.
The "shutter speed" is set by the duration of the sensing period, which
is, more or less, set by the width of a clock pulse. The frame rate is
set by the clock speed. The normal bottleneck for frame rate is the
speed of the memory device in use, and the fastest frame rate cameras
tend to use a first in first out RAM buffer with a second or two of data
in it, and when you hit the "record" button, it dumps the contents of
the buffer onto a hard drive or other storage device.
On 12/07/2022 09:16, Brian Gaff wrote:
> I always thought that semiconductor cameras were merely moving memory about
> in silicon. Every chunk is a frame, and its then handled from the place it
> has gone to depending on the system that is used. One assumes as you can now
> get extremely fast frame rates for video cameras, that this is dictated by
> how fast memory can be copied and processed.
>
> Brian
>
--
Tciao for Now!
John.
send it to a local memory buffer and on to the main stirage, or to scan
a row or pixel at a time, then poke the data stream directly into the
main storage.
The "shutter speed" is set by the duration of the sensing period, which
is, more or less, set by the width of a clock pulse. The frame rate is
set by the clock speed. The normal bottleneck for frame rate is the
speed of the memory device in use, and the fastest frame rate cameras
tend to use a first in first out RAM buffer with a second or two of data
in it, and when you hit the "record" button, it dumps the contents of
the buffer onto a hard drive or other storage device.
On 12/07/2022 09:16, Brian Gaff wrote:
> I always thought that semiconductor cameras were merely moving memory about
> in silicon. Every chunk is a frame, and its then handled from the place it
> has gone to depending on the system that is used. One assumes as you can now
> get extremely fast frame rates for video cameras, that this is dictated by
> how fast memory can be copied and processed.
>
>
--
Tciao for Now!
John.
Dave W
Jul 12, 2022, 2:42:26 PM7/12/22
to
whole frame represents one instant in time.
--
Dave W
NY
Jul 13, 2022, 3:49:46 AM7/13/22
to
"Dave W" <dave...@yahoo.co.uk> wrote in message
news:51grchli30np3qseu...@4ax.com...
That's exacerbated by the fact that many mini cameras mounted on aeroplane
windows to show a TV presenter can only adjust the exposure by varying the
shutter speed, because they have a primitive fixed-iris lens. This means
that you get *sharp* images of the disjointed propeller blades rather than
blurred ones with a 1/25 sec shutter speed.
news:51grchli30np3qseu...@4ax.com...
windows to show a TV presenter can only adjust the exposure by varying the
shutter speed, because they have a primitive fixed-iris lens. This means
that you get *sharp* images of the disjointed propeller blades rather than
blurred ones with a 1/25 sec shutter speed.
Brian Gaff
Jul 13, 2022, 4:51:51 AM7/13/22
to
Besides, the definition of a single moment is meaningless everything takes
time or we would be in the present for ever.
news:talteo$2akra$1...@dont-email.me...
time or we would be in the present for ever.
Brian
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"NY" <m...@privacy.invalid> wrote in message
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Richard Tobin
Jul 13, 2022, 5:55:01 AM7/13/22
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In article <tam135$2avon$1...@dont-email.me>,
-- Richard
Brian Gaff <brian...@gmail.com> wrote:
>Besides, the definition of a single moment is meaningless everything takes
>time or we would be in the present for ever.
How long does 6 o'clock last?
>Besides, the definition of a single moment is meaningless everything takes
>time or we would be in the present for ever.
-- Richard
Mark Carver
Jul 13, 2022, 6:42:14 AM7/13/22
to
Brian Gaff
Jul 13, 2022, 10:42:03 AM7/13/22
to
Lets just say that even if you had a clock wired into your brain, by the
time you became aware it was 6 it would be after 6.
Can you experience deja Vu for the first time and all that.
news:tam4pi$kfs$1...@macpro.inf.ed.ac.uk...
time you became aware it was 6 it would be after 6.
Can you experience deja Vu for the first time and all that.
Brian
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"Richard Tobin" <ric...@cogsci.ed.ac.uk> wrote in message
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williamwright
Jul 13, 2022, 5:29:33 PM7/13/22
to
On 13/07/2022 10:54, Richard Tobin wrote:
Bill
Liz Tuddenham
Jul 14, 2022, 4:38:27 AM7/14/22
to
childish?
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(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
Brian Gaff
Jul 15, 2022, 8:20:06 AM7/15/22
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Yes all the dog mess would reverse back into the dogs.
news:jj8rpr...@mid.individual.net...
Brian
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"williamwright" <wrights...@f2s.com> wrote in message
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NY
Jul 15, 2022, 9:18:13 AM7/15/22
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(top-posting for Brian)
That would be one hell of a sight ;-)
news:tarm1h$322mi$1...@dont-email.me...
That would be one hell of a sight ;-)
news:tarm1h$322mi$1...@dont-email.me...
> Yes all the dog mess would reverse back into the dogs.
> "williamwright" <wrights...@f2s.com> wrote in message
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