19-09-2018, 12:58 PM
(This post was last modified: 19-09-2018, 01:03 PM by ppppenguin.)
Thanks for what must be an insider's view of what happened at the BBC. I'm not surprised the CO6/501 (the original analogue 625 to 405 converter) was modified to do the reverse conversion. Something like that was clearly needed. Likewise when the BBC found that its aging CO6/501 converters were a problem they developed the digital CO6/509. It's interesting that the CO6/502 was kept in service for a lot longer than the CO6/501. I guess it was in a friendlier environment (archives, not transmitter sites) and so had more skilled and frequent attention. The CO6/509 could probably have been modified to do 405 to 625 but by the time the ACE was available the 405 service was either very near to closing down or had actually done so.
Since the ACE was a framestore converter, originally conceived for PAL<>NTSC conversion, monochrome line number conversion was a trivial task for it.
A few years ago I was approached by a production company who wanted to recover some 405 material. I understood that this was footage of the Beatles on 2" quad and they had access to a working VR2000. Possibly at the BBC though they didn't specify. In fact they were fairly secretive about the whole thing. I said I would look at making a 405 to 625 converter for the job but I was busy with other work and they wanted a quick result. I advised them to use optical conversion which I believe they did. A modern HD camera looking at a decent 405 monitor, possibly the one on the gantry of the VR2000, should be capable of decent results. From my own experience of ad-hoc optical conversion I reckoned to raise the monitor black level slightly and compensate this in the camera. I also suggested reducing the monitor height to merge the scan lines. This is a good way to eliminate moire patterning. The aspect ratio change could easily be put right in post production. When I did optical conversion I simply defocussed the camera slightly.
Incidentally, the introductory part of the CO6/501 manual is available online: http://www.bbceng.info/ti/eqpt/CO6_501.pdf Some modules of the CO6/501 are also available such as this: http://www.bbceng.info/ti/eqpt/PA1_517.pdf
Since the ACE was a framestore converter, originally conceived for PAL<>NTSC conversion, monochrome line number conversion was a trivial task for it.
A few years ago I was approached by a production company who wanted to recover some 405 material. I understood that this was footage of the Beatles on 2" quad and they had access to a working VR2000. Possibly at the BBC though they didn't specify. In fact they were fairly secretive about the whole thing. I said I would look at making a 405 to 625 converter for the job but I was busy with other work and they wanted a quick result. I advised them to use optical conversion which I believe they did. A modern HD camera looking at a decent 405 monitor, possibly the one on the gantry of the VR2000, should be capable of decent results. From my own experience of ad-hoc optical conversion I reckoned to raise the monitor black level slightly and compensate this in the camera. I also suggested reducing the monitor height to merge the scan lines. This is a good way to eliminate moire patterning. The aspect ratio change could easily be put right in post production. When I did optical conversion I simply defocussed the camera slightly.
Incidentally, the introductory part of the CO6/501 manual is available online: http://www.bbceng.info/ti/eqpt/CO6_501.pdf Some modules of the CO6/501 are also available such as this: http://www.bbceng.info/ti/eqpt/PA1_517.pdf
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
