[opendtv] Re: HD vs. 625 vs. 525 vs. 405

Okay I understand your definition and I was trying to say the same thing 
from a different perspective. In system A, the E.M.I. engineers did not 
account for the loss of the vertical resolution.  And I am aware of the 
Kell, Bedford and Trainer "Experimental Television Station" Proceedings of 
the I.R.E. Volume 22 - 1934!

In system M as you indicate, the Kell factor was applied to reduce the 
horizontal resolution by the factor of 0.7 to account for the apparent 
vertical resolution loss. In system A, the horizontal resolution is higher 
relative to the vertical resolution because the apparent loss was not taken 
account of.

Maybe it would be more correct to say the Kell Factor was not applied to 
system A.  That is what I meant by saying the Kell Factor is unity. (I will 
not bring interlace into this as it would further muddy the issue.)

Perhaps then the sharpness of 405 received pictures can be accounted for by 
the excessive horizontal resolution applied.

Terry Harvey



At 12:09 PM 8/28/2004 -0400, Mark Schubin wrote:
>Terry Harvey wrote:
>
> >The definition of Kell Factor is the number obtained by dividing the raster
> >pitch distance by the width of the picture resolution elements.
> >
>No, it is not.  The common definition of the Kell factor is the
>reduction in vertical resolution from the number of scanning lines
>(although, in the age of fixed-pixel displays, it has also been applied
>to the reduction in hirizontal resolution from the number of active
>samples per line).
>
> >Recall that system A was developed in 1935/36, before Kell and others
> >discovered that the interlaced vertical resolution was not ideal.
> >
>Kell did his work in the early 1930s, before System A was broadcast.
>
>I have extensively researched Kell's work.  I would suggest that you
>look up the Proceedings of the IRE.
>
>TTFN,
>Mark
>
>
>
>
>
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