In article <ja0ktpFgm4bU1@mid.individual.net>,
Mark Carver <mark.carver@invalid.invalid> wrote:
> On 23/03/2022 10:17, charles wrote:
> >
> > Back in the 1970s, I was showing off Ceefax at the TV exhibition in
> > Montreaux.
> Crystal Palace had one hell of a range !

no, the signal was coming from a VT on the Ampex stand 2 floors down. But,
I could get R2 on my car radio (expect under the overhead tram wires.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 23/03/2022 14:11, charles wrote:
> In article <ja0ktpFgm4bU1@mid.individual.net>,
> Mark Carver <mark.carver@invalid.invalid> wrote:
>> On 23/03/2022 10:17, charles wrote:
>>> Back in the 1970s, I was showing off Ceefax at the TV exhibition in
>>> Montreaux.
>> Crystal Palace had one hell of a range !
> no, the signal was coming from a VT on the Ampex stand 2 floors down.
Ah, very good. Back in those days even almost-rival manufacturers would
happily swap feeds between stands.
Lots of Hum-Buckers everywhere of course. SDI took the fun out of that,
but by then the 'grown-ups' had put a stop to those sort of things.
> I could get R2 on my car radio (expect under the overhead tram wires.
Yep, good old Droitwich normally made it with the radio near the hotel
room window

In article <ja0t2oFi92cU1@mid.individual.net>,
Mark Carver <mark.carver@invalid.invalid> wrote:
> On 23/03/2022 14:11, charles wrote:
> > In article <ja0ktpFgm4bU1@mid.individual.net>,
> > Mark Carver <mark.carver@invalid.invalid> wrote:
> >> On 23/03/2022 10:17, charles wrote:
> >>> Back in the 1970s, I was showing off Ceefax at the TV exhibition in
> >>> Montreaux.
> >> Crystal Palace had one hell of a range !
> > no, the signal was coming from a VT on the Ampex stand 2 floors down.
> Ah, very good. Back in those days even almost-rival manufacturers would
> happily swap feeds between stands.

The main member of the Ampex team had been at Woodnorton with me, as had
the boss of the PYE stand.

> Lots of Hum-Buckers everywhere of course.

indeed. 3v hum and 1v video. Probably different phases on each floor.

> SDI took the fun out of that,
> but by then the 'grown-ups' had put a stop to those sort of things.
> > I could get R2 on my car radio (expect under the overhead tram wires.
> Yep, good old Droitwich normally made it with the radio near the hotel
> room window

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 23/03/2022 12:32, NY wrote:
>
> My scanner tends to produce better results (better tonal range) if I
> scan as a positive and correct in software, rather than scan as a (B&W)
> negative. But negs in general (and especially colour ones) are a lot
> more difficult to get good scans from than positive slides.

Actually I disagree, at least as far as my scanner goes, it's an old HP
5490C (Model C9850A), the bummer being that I can't get 64-bit drivers
for it, so have to use it with either XP or Linux. However it does have
an illuminated neg/slide holder, and I can choose in the menu of its
associated software which I'm scanning, and it'll apply any necessary
corrections automatically. The results from scanning the original
negatives or slides are almost always far superior to those from
scanning prints made from them, in terms of surface damage, contrast,
and colours.

> Thankfully all
> the slides I chose seem to have been something over than Kodachrome so
> the IR dirt-reduction algorithm worked OK (unlike Agfa and Kodak
> Ektachrome, Kodachrome has an emulsion which is not uniformly
> transparent to IR, so the algorithm which uses IR to look for dirt and
> dust on the film doesn't work because it sees darker parts of the image
> as dirt).

Kodachrome was a favourite film for me, the worst thing about the slides
made from it are that the cardboard surrounds disintegrate and leave
dust over the slides themselves. AFAIAA, my scanner doesn't have a dirt
removal function as you describe, and it took me the best part of two
years to go through all the family albums scanning or photographing them
and cleaning up the digitised results. The results vary, with the best
being really very good, but some of the material had degraded so far
that little post-processing could be done to improve it.

--

Fake news kills!

I may be contacted via the contact address given on my website:
www.macfh.co.uk

On Wed, 23 Mar 2022 11:29:54 -0000, "NY" <me@privacy.invalid> wrote:

>Apparently when CRTs were included in vision for a film camera or a TV
>camera, the camera was synchronised with the video sync to avoid a rolling
>bar on the screen image: maybe even run the camera without film, checking
>for a visible bar in the viewfinder and adjusting phase to move it
>off-screen.

It's not possible to "overcrank" or "undercrank" a TV camera to a
different frame rate in the same way as a film camera, so it can't
actually be synchronised to anything other than system sync pulses.

Computer CRT scanning rates were unrelated to TV rates and usually
much higher, so electrically synchronising the cameras would have been
out of the question.

It's actually the exposure time of the camera, not synchronisation,
that was adjusted to accommodate in-vision computer CRT displays, and
it only became possible with the advent of solid state "chip" cameras.
The start of the time interval for which the chip was sensitive to
light could be adjusted, sometimes continuously and sometimes in steps
depending on the design of the camera, but the readout time at the end
of that interval had to be synchronised to television system pulses.
There would still be randomly positioned horizontal bars on the CRT
display, but with zero overlap, which would be less visible as long as
the camera didn't pan.

It was easy to confirm this by pointing a camera at a television
monitor displaying something bright with the same scanning rate as the
camera, while adjusting the electronic shutter control of the camera.
It would be the upper edge of the bright bar, i.e. the start of the
exposure time, that would move as the control was adjusted.

Rod.

On Wed, 23 Mar 2022 12:37:18 -0000, "NY" <me@privacy.invalid> wrote:

>"Max Demian" <max_demian@bigfoot.com> wrote in message
>news:E82dnS-guvgpl6b_nZ2dnUU7-c3NnZ2d@brightview.co.uk...
>> It's not immediately obvious which displays work by reflection and which
>> by producing light. LCDs work by reflection, but what if it relies on a
>> backlight? There are shopping coupons which are scanned by a laser in the
>> shop, but, if you don't have access to a printer, you are supposed to be
>> able to scan the bar/QR code on a smartphone screen; how does that work?
>> What if the display is OLED?
>
>Like you, I've always wondered how laser barcode scanners manage to scan a
>backlit LED screen rather than a reflective paper coupon (or an LCD screen).
>Scanners in shops seem to have a switchable setting which maybe turns the
>laser off and moves the sensor (or relies on movement of the phone screen
>past the scanner) to sense the horizontal axis of the bar code.

The first time I saw a checkout scanner cope with the barcode on a
crumpled bag of frozen peas dripping with moisture, and without the
operator needing to pause as she whizzed it past the scanning window,
I was amazed that anyone ever thought such a system could work at all.

Rod.

"Roderick Stewart" <rjfs@escapetime.myzen.co.uk> wrote in message
news:4gbo3h5lur8cvdlruqpkfs38ak4bfh2ivl@4ax.com...
> On Wed, 23 Mar 2022 11:29:54 -0000, "NY" <me@privacy.invalid> wrote:
>
>>Apparently when CRTs were included in vision for a film camera or a TV
>>camera, the camera was synchronised with the video sync to avoid a rolling
>>bar on the screen image: maybe even run the camera without film, checking
>>for a visible bar in the viewfinder and adjusting phase to move it
>>off-screen.
>
> It's not possible to "overcrank" or "undercrank" a TV camera to a
> different frame rate in the same way as a film camera, so it can't
> actually be synchronised to anything other than system sync pulses.

What I described related to film cameras, hence my reference to running
without film to see the effect through the viewfinder to check for the
*phase* of the shutter opening, with the expectation that the *frequency*
would be accurately controlled at 25 fps by the crystal which keeps the
sepmag sound in sync with the film. Maybe the cable takes the place of the
crystal as a source of frame sync. I imagine with a free-running TV camera
(when recording locally) you could use the TV's video signal to sync the
camera to the TV source, so the raster of the camera matched the raster of
the TV source.

> Computer CRT scanning rates were unrelated to TV rates and usually
> much higher, so electrically synchronising the cameras would have been
> out of the question.
>
> It's actually the exposure time of the camera, not synchronisation,
> that was adjusted to accommodate in-vision computer CRT displays, and
> it only became possible with the advent of solid state "chip" cameras.
> The start of the time interval for which the chip was sensitive to
> light could be adjusted, sometimes continuously and sometimes in steps
> depending on the design of the camera, but the readout time at the end
> of that interval had to be synchronised to television system pulses.
> There would still be randomly positioned horizontal bars on the CRT
> display, but with zero overlap, which would be less visible as long as
> the camera didn't pan.
>
> It was easy to confirm this by pointing a camera at a television
> monitor displaying something bright with the same scanning rate as the
> camera, while adjusting the electronic shutter control of the camera.
> It would be the upper edge of the bright bar, i.e. the start of the
> exposure time, that would move as the control was adjusted.

I would have thought that to be able to use a TV camera to view a TV screen,
you want the shutter speed to be the full 1/25 second, especially if the TV
screen fills the majority for the frame. If the screen fills (for example)
50 lines of the camera, you can use a correspondingly shorter shutter speed
as the camera will only see the TV screen for 50/625 * 1/25 second.

I'm always amazed at how a simple video camera (as long as it is UK-spec 25
fps) with no sync to the TV can give a stable picture with no visible
flicker or rolling bar. I presume if you wait long enough you may see a bar
roll through the picture at a rate of (TV frame rate - camera frame rate) if
the camera is free-running and is not running at precisely 25 fps due to
normal component tolerances. Sadly a lot of simple cameras (GoPro, cameras
in mobile phones or tablets, etc) are preset to run only at the US 29.97 fps
frame rate. Actually, a lot of that sort of camera seem to run at 30 fps, so
no doubt there would need to be the old 1000/1001 drop-frame correction.
It's a great shame that all video cameras (including mobile phones, GoPro
etc) aren't designed to be switchable between the two frame rates, to
satisfy the European, Australian, African, Arabian etc market which I
presume is a sizable minority compared with the US/Canada/Japanese market.

On 23/03/2022 12:37, NY wrote:
> "Max Demian" <max_demian@bigfoot.com> wrote in message
> news:E82dnS-guvgpl6b_nZ2dnUU7-c3NnZ2d@brightview.co.uk...

>> It's not immediately obvious which displays work by reflection and
>> which by producing light. LCDs work by reflection, but what if it
>> relies on a backlight? There are shopping coupons which are scanned by
>> a laser in the shop, but, if you don't have access to a printer, you
>> are supposed to be able to scan the bar/QR code on a smartphone
>> screen; how does that work? What if the display is OLED?
>
> Like you, I've always wondered how laser barcode scanners manage to scan
> a backlit LED screen rather than a reflective paper coupon (or an LCD
> screen). Scanners in shops seem to have a switchable setting which maybe
> turns the laser off and moves the sensor (or relies on movement of the
> phone screen past the scanner) to sense the horizontal axis of the bar
> code.

I've just scanned an eVoucher on my Motorola E5 Play at the ASDA self
checkout - actually the assistant held it at the right angle, but I
don't recall seeing her switch anything.

--
Max Demian

On Saturday, 19 March 2022 at 10:45:02 UTC, Brian Gaff (Sofa) wrote:
> May seem a daft question, but in the old days of tubes, there were various
> patterns of shadow masks on them. Some tended to be noticeable as vertical
> stripes, others as little triads, And when we started to get digital video
> as in games, it was not unusual to see oval circles on things, due to the
> pixel being displayed oblong instead of square, so to speak.
> Brian
>
>
>
> --
>
> This newsgroup posting comes to you directly from...
> The Sofa of Brian Gaff...
> bri...@blueyonder.co.uk
> Blind user, so no pictures please
> Note this Signature is meaningless.!

It seems Samsung has opted for triangular on its new OLED TV's, but: -

https://www.techradar.com/news/samsung-might-have-a-problem-with-its-new-oled-tvs-sub-pixels

On Thu, 24 Mar 2022 14:12:12 -0000, "NY" <me@privacy.invalid> wrote:

>I would have thought that to be able to use a TV camera to view a TV screen,
>you want the shutter speed to be the full 1/25 second, especially if the TV
>screen fills the majority for the frame. If the screen fills (for example)
>50 lines of the camera, you can use a correspondingly shorter shutter speed
>as the camera will only see the TV screen for 50/625 * 1/25 second.

Vertical scan is actually 50Hz not 25, but the principle is the same.
To photograph TV CRT monitors displaying signals with the same frame
rate as the camera, chip cameras should be set to use no shutter at
all, so they are sensitive to light 100% of the time.

There will still be a horizontal split, but if the signals the
monitors are displaying are derived from the same sync pulses as the
cameras (which would be usual in a studio setting) then it will be off
the screen.

Rod.

On 25/03/2022 10:11, Roderick Stewart wrote:
> Vertical scan is actually 50Hz not 25, but the principle is the same.

But if interlaced, e.g. standard analogue TV, the whole picture requires
two vertical scans, one for odd and one for even lines.

On 25/03/2022 21:44, David Woolley wrote:
> But if interlaced, e.g. standard analogue TV,

Analogue TV? Sorry, don't remember...

Bill

"David Woolley" <david@ex.djwhome.demon.invalid> wrote in message
news:t1ld4c$ce2$1@dont-email.me...
> On 25/03/2022 10:11, Roderick Stewart wrote:
>> Vertical scan is actually 50Hz not 25, but the principle is the same.
>
> But if interlaced, e.g. standard analogue TV, the whole picture requires
> two vertical scans, one for odd and one for even lines.

I presume that digital tuners and recorders that have an analogue SCART or
RF output for compatibility with analogue TVs will *always* output
interlaced, even if the digital source happens to be 25p (SD or HD), because
analogue signals are *defined* to be interlaced, and 25p would look very
flickery. Obviously in the case of HD, the tuner/PVR also has to downscale
from 1080 to 576 lines.

I was musing on this, and allied to this of course is resolution and aspect
ratio as well. It seems not all of these have agreement exactly, so they
nowadays use software to approximate things so they look correct.

Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
briang1@blueyonder.co.uk
Blind user, so no pictures please
Note this Signature is meaningless.!
"R. Mark Clayton" <notyalckram@gmail.com> wrote in message
news:8b1b2163-9dd7-45ac-8891-c633a268e76dn@googlegroups.com...
> On Saturday, 19 March 2022 at 10:45:02 UTC, Brian Gaff (Sofa) wrote:
>> May seem a daft question, but in the old days of tubes, there were
>> various
>> patterns of shadow masks on them. Some tended to be noticeable as
>> vertical
>> stripes, others as little triads, And when we started to get digital
>> video
>> as in games, it was not unusual to see oval circles on things, due to the
>> pixel being displayed oblong instead of square, so to speak.
>> Brian
>>
>>
>>
>> --
>>
>> This newsgroup posting comes to you directly from...
>> The Sofa of Brian Gaff...
>> bri...@blueyonder.co.uk
>> Blind user, so no pictures please
>> Note this Signature is meaningless.!
>
> It seems Samsung has opted for triangular on its new OLED TV's, but: -
>
> https://www.techradar.com/news/samsung-might-have-a-problem-with-its-new-oled-tvs-sub-pixels

On Sat, 26 Mar 2022 22:07:18 -0000, "NY" <me@privacy.invalid> wrote:

>"David Woolley" <david@ex.djwhome.demon.invalid> wrote in message
>news:t1ld4c$ce2$1@dont-email.me...
>> On 25/03/2022 10:11, Roderick Stewart wrote:
>>> Vertical scan is actually 50Hz not 25, but the principle is the same.
>>
>> But if interlaced, e.g. standard analogue TV, the whole picture requires
>> two vertical scans, one for odd and one for even lines.
>
>I presume that digital tuners and recorders that have an analogue SCART or
>RF output for compatibility with analogue TVs will *always* output
>interlaced, even if the digital source happens to be 25p (SD or HD), because
>analogue signals are *defined* to be interlaced, and 25p would look very
>flickery. Obviously in the case of HD, the tuner/PVR also has to downscale
>from 1080 to 576 lines.

25p wouldn't work directly with an analogue display, which is designed
to scan vertically at 50Hz. It wouldn't synchronise and you wouldn't
get a stable display.

Rod.

On Wed, 23 Mar 2022 15:35:52 +0000, Mark Carver
<mark.carver@invalid.invalid> wrote:

>>>> Back in the 1970s, I was showing off Ceefax at the TV exhibition in
>>>> Montreaux.
>>>
>>> Crystal Palace had one hell of a range !
>>
>> no, the signal was coming from a VT on the Ampex stand 2 floors down.
>
> Ah, very good. Back in those days even almost-rival manufacturers would
> happily swap feeds between stands.
> Lots of Hum-Buckers everywhere of course. SDI took the fun out of that,
> but by then the 'grown-ups' had put a stop to those sort of things.
>
>> I could get R2 on my car radio (expect under the overhead tram wires.
>
> Yep, good old Droitwich normally made it with the radio near the hotel
> room window

I picked it up (R4 then of course) on higher ground in Majorca on the
bog-standard hire car radio, about 25 years ago.

On Wednesday, March 30, 2022 at 12:31:09 AM UTC+5:30, Paul Ratcliffe wrote:
> On Wed, 23 Mar 2022 15:35:52 +0000, Mark Carver
> <mark....@invalid.invalid> wrote:
>
> >>>> Back in the 1970s, I was showing off Ceefax at the TV exhibition in
> >>>> Montreaux.
> >>>
> >>> Crystal Palace had one hell of a range !
> >>
> >> no, the signal was coming from a VT on the Ampex stand 2 floors down.
> >
> > Ah, very good. Back in those days even almost-rival manufacturers would
> > happily swap feeds between stands.
> > Lots of Hum-Buckers everywhere of course. SDI took the fun out of that,
> > but by then the 'grown-ups' had put a stop to those sort of things.
> >
> >> I could get R2 on my car radio (expect under the overhead tram wires.
> >
> > Yep, good old Droitwich normally made it with the radio near the hotel
> > room window
> I picked it up (R4 then of course) on higher ground in Majorca on the
> bog-standard hire car radio, about 25 years ago.
One of my friends have been using autoclicker (the most latest version) and told me that he is having great experience with op auto clicker despite having some sort of mixed opinions about the software. Here is the link https://autoclicker.online/