Was it possible to convert 625 lines to 405 lines at the time of 405 switch off?

[AidanLunn]

Originally Posted by merlinmaxwell

Was 405 converted to 625 for broadcast?

In September 85, Channel Four went on a spree of repeating archive ITV shows, many from their original videotapes, for the 30th anniversary of ITV (in those days, Channel Four was also under the edict of the IBA, so was considered ITV's answer to BBC2). IIRC, many of these programmes, like early Callan, were from the 405 tapes, and as the people doing the conversion at the time didn't have access to an electronic convertor, an optical one was used. Obviously what was transmitted was from 625-line 1" tape copies, so was not a "live" conversion.

When we held the Eurovision Song Contest in 1960 and again in 1963, this may have been made in 405 here and converted live up to 625 for the rest of the network (apart from France, on 819-lines at this point still?)

[FERNSEH]

Certain BRC TV sets, Ferguson, HMV, Marconi and Philco made between 1961 to early 1963 could be converted to full dual standard operation with an additional IF amplifier unit and an UHF tuner. A special back cover was made to accommodate the unit which was attached to the upper deck of the 700 phase II and 800 series chassis. Except for a couple of wire links which had to be cut this was a fully plug-in unit. A good number of sets were converted but non survived up to the 405 switch-off.

DFWB.

[emeritus]

The shutter speed of my original VHS-C camcorder. a JVC GR-M7, can be set to 1/60 as well as 1/50 sec. The manual says it can be useful for reducing flicker in fluorescent lighting, but I found that the 1/60 sec setting allowed me to include NTSC TV monitors in the scene without the wide dark bars you usually get. Not perfect, as some very thin lines are visible, but visually it was much better than the alternative. Unfortunately my later JVC digital camcorder does not have the 1/60 option.

I did once use the 1/50 setting in France for SECAM to PAL conversion. That was in 1999. We were at my brother-in-law's at the time: his house was virtually on the line of maximum totality, and the clouds moved completely away just before totality. He had an excellent Schneider 15" TV and I just set the camcorder up on a tripod and zoomed in to fill the screen. A line was visible in a fixed, but random position, on the camera's monitor which changed position every time I powered up, and by repeatedly switching the camera off and on again I managed to arrive at a condition where the Camera and TV were in perfect synch and the line was not visible. I thereafter used the Pause control to record the day's programmes about the event. The camera maintained Synch for at least an hour without needing further adjustment.

Older video cameras with tube imagers having a relatively long response time could also be used for standards conversion, as was mentioned in a thread on this forum some time ago. I found this out myself years ago in the context of copying some of my 8mm cine to video , and found that, using an early Panasonic VHS-C camcorder, I got no discernable flicker, regardless of how I adjusted the projector speed (nominally 16 frames per second). The later generation of cameras had solid state imagers which need precise control of speed to eliminate flicker, and I have found it almost impossible to find any info on current camcorders about provision for adjusting shutter speed to 1/50 sec manually. So a vintage video camera/camcorder would seem to be the thing to use for standards conversion by pointing a video camera at a monitor.

[julie_m]

Originally Posted by emeritus

So a vintage video camera/camcorder would seem to be the thing to use for standards conversion by pointing a video camera at a monitor.

If you can find one without too many dead pixels .....

[peter_scott]

Sony TRV22 palmcorder has various slow shutter modes and works quite well without bars.

https://www.youtube.com/watch?v=4i3VmIMoeUk

Peter

[Synchrodyne]

Originally Posted by merlinmaxwell

Was 405 converted to 625 for broadcast?

The attached may be of interest. One infers that as of mid-1961, optical conversion was still the norm for the BBC. So it seems probable that RTE did likewise, at least initially.

There may also have been what was effectively a roundabout 405-line to 625-line conversion for export purposes. I recall in NZ back in the 1960s that following public comment about the rather poor image quality of some UK programmes then being shown, it was explained that that they were videotaped at 405-lines, then transferred to film for export. I think that it applied mainly to some ITV/Granada programmes.

Cheers,

[red16v]

Originally Posted by Nicklyons2

I met a purpose built optical (field) standards converter many years ago and I'm almost certain it was a Tektronix - I believe the BBC had 1 or 2 similar for emergency use if the electronic version acted up. The most remarkable feature to me, at the time, was the smearing; to get rid of the 10Hz flicker the display screen was long persistence phosphor. I remember watching a tennis match on it - the NTSC input looked fine but the PAL output looked as if it was shot on a very 'laggy' vidicon camera.

Nowadays it is easy to get rid of the flicker by adjusting the camera which is doing the shooting; most modern up-market cameras have a tuneable 'slit-scan' shutter which can be set to match the monitor's frame rate exactly. This is often necessary when videoing computer monitors which can run at a variety of frame rates.

ATV at Elstree originally had an optical standards converter, it was made by Bosch. It was later supplanted by an all electronic converter - a McMichael ACE if I recall correctly.

Not quite sure what 'up market' cameras you refer to, I know of no modern studio broadcast camera using a slit scan shutter technique? Philips/BTS produced studio cameras with mechanical shutters, but that was not to do with anything concerning 'slit scan'. I'm not 100% up to date with broadcast cameras these days so I'm very happy to be corrected on this topic.

[julie_m]

It probably isn't an actual mechanical shutter; just emulated electronically, by munging the digital signals from the CCD sensor array. If there are definite dim and bright bands down the image, or the brightness of the entire image is varying up and down, this means that it is not being scanned at exactly the same rate as it is being painted, and the amount by which the brightness of the phosphor has decayed since the beam struck it is varying. The scanning speed is adjusted, until the camera is following the electron beam in real time (ideally, the camera should be seeing the exact same spot on the phosphor where the electron beam is striking it). The maths is exactly the same as controlling the speed of a DC brushless motor; you want to get a the camera's line and field timings to match those of the programme source.

[Nicklyons2]

The 'shutter' referred to is an electronic variable read rate from the CCDs. Most Ikegami and Sony cameras I have encountered in the last 20 years or so have had this facility. I don't want to bore everyone with a massive list of models but start with Sony BVP7 and into full HD, HDW750 etc.

Without these shutters it would be almost impossible to 'shoot' in environments where mobile phone or computer screens were in view.