03-04-2017, 08:32 AM
(This post was last modified: 03-04-2017, 08:35 AM by Murphyv310.)
Hi.
Some interesting comments here.
Steve I've read your reply with interest. Although the frame rate between 405 & 625 are the same the "writing" speed between the two standards are significantly different. Refugee has indeed a very good point with the scope and the very same can be reproduced on a TV screen so long as the line scan and EHT are not linked as varying line speeds effect EHT and thus brightness. If you observe a frame collapse thus one line on lower line speeds the result is brighter and on fast line rates the line is duller. This has to do with the writing speed, the phosphors have less time to "charge" on a faster line speed with a obviously faster drawing time.
As I previously remarked the "overall" brightness between 405 & 625 will be little different due to "perceived" brightness, although the writing speed is faster on 625 more of the phosphors will be"activated" and the eye will adjust to this even though each line will be slightly less bright.
I recently made up a little board with video amp, inverted, syncs etc to use on the scope in Z mod, It will resolve 180 lines to 819 lines, now Refugees comment would mean that brightness would be poor on 819 but bright on 180, in practice there is only a marginal difference as on 819 as we are using considerably more phosphors than on 180.
The comment about valve tuners on UHF doesn't stand up. by the mid 60's many sets had transistorised tuners but still we had the milky pictures on 625, In fact before I started working we had a British Relay set and BBC 2 was always poor with no depth of contrast and no punch, like I say come duplication all of a sudden 625 livened up giving a big improvement.
I also remember my Philips T-Vette I had and it too did the same just after duplication with 625 very much giving 405 a run for it's money and it had only one valve..... the EHT rectifier.
OK Valve tuners were pretty crap but I can assure you they were not the only reason for UHF's ills.
Some interesting comments here.
Steve I've read your reply with interest. Although the frame rate between 405 & 625 are the same the "writing" speed between the two standards are significantly different. Refugee has indeed a very good point with the scope and the very same can be reproduced on a TV screen so long as the line scan and EHT are not linked as varying line speeds effect EHT and thus brightness. If you observe a frame collapse thus one line on lower line speeds the result is brighter and on fast line rates the line is duller. This has to do with the writing speed, the phosphors have less time to "charge" on a faster line speed with a obviously faster drawing time.
As I previously remarked the "overall" brightness between 405 & 625 will be little different due to "perceived" brightness, although the writing speed is faster on 625 more of the phosphors will be"activated" and the eye will adjust to this even though each line will be slightly less bright.
I recently made up a little board with video amp, inverted, syncs etc to use on the scope in Z mod, It will resolve 180 lines to 819 lines, now Refugees comment would mean that brightness would be poor on 819 but bright on 180, in practice there is only a marginal difference as on 819 as we are using considerably more phosphors than on 180.
The comment about valve tuners on UHF doesn't stand up. by the mid 60's many sets had transistorised tuners but still we had the milky pictures on 625, In fact before I started working we had a British Relay set and BBC 2 was always poor with no depth of contrast and no punch, like I say come duplication all of a sudden 625 livened up giving a big improvement.
I also remember my Philips T-Vette I had and it too did the same just after duplication with 625 very much giving 405 a run for it's money and it had only one valve..... the EHT rectifier.
OK Valve tuners were pretty crap but I can assure you they were not the only reason for UHF's ills.
