SKF NTSC in England

[old_tv_nut]

[Electronic M]

Interesting. That may be the oldest medical telecast in NTSC I've seen pictures of. I remember reading the account of someone who worked for them saying the pre-NTSC field sequential equipment remained in service until 1958.

[old_tv_nut]

Interesting that they just attached a mirror to an OR light to get the overhead view. Looks very last-minute ad hoc.
I wonder if they reversed the scan in the camera to get the handedness correct.

In a way, the switch to NTSC was a step backwards for this closed-circuit use because the color resolution was so much poorer than the CBS system. The bulk of the three tube camera was not an advantage either.

[Penthode]

Originally Posted by old_tv_nut

In a way, the switch to NTSC was a step backwards for this closed-circuit use because the color resolution was so much poorer than the CBS system. The bulk of the three tube camera was not an advantage either.

Curious about your statement step backward? Agreed there is the registration issue with a three tube camera. But unless the field sequential channel bandwidth was made wider, the resolution would have been noticably worse. CBS Field Sequential for a 6 MHz channel optimally would be only about 340 line to even bring the Kell Factor to 0.6. CBS was dependent upon crispening circuits to make up for the poor horizontal resolution.

On the other hand, this is a closed circuit set up which would have meant channel bandwidth would not be restricted. And the new tricolor CRTs under development by both CBS and RCA could have been used.

[old_tv_nut]

Originally Posted by Penthode

Curious about your statement step backward? Agreed there is the registration issue with a three tube camera. But unless the field sequential channel bandwidth was made wider, the resolution would have been noticably worse. CBS Field Sequential for a 6 MHz channel optimally would be only about 340 line to even bring the Kell Factor to 0.6. CBS was dependent upon crispening circuits to make up for the poor horizontal resolution.

On the other hand, this is a closed circuit set up which would have meant channel bandwidth would not be restricted. And the new tricolor CRTs under development by both CBS and RCA could have been used.

The chroma bandwidth of NTSC is much less than the luma bandwidth. The field sequential system has the same resolution for color details as for luminance details, although this is less than the NTSC luminance resolution. In closed circuit use, NTSC can have greater luma bandwidth but still has the lower chroma bandwidth. For another thing, the luminance bandwidth in the NTSC monitors was compromised by the subcarrier trap. They did not have comb filters.

In closed-circuit medical use, the deficiency in the field sequential vertical resolution due to the reduced number of scan lines could be compensated by zooming in when necessary.

[old_tv_nut]

By the way, the use of shadow mask CRTs for a field sequential system was a bit of a pipe dream, as it would reduce picture brightness by two thirds.