Re: Luma discussions

Of course you're free to do so, but (FYI) this is not an Internet forum.


On 2017-02-20 10:42, Bo Herrmannsen wrote:
> i have changed the subject as it did not relate to my initial thread and
> got bored of reading things that i was not interested in
>
> 2017-02-20 10:00 GMT+01:00 <groepaz@gmx.net <mailto:groepaz@gmx.net>>:
>
>     On Monday 20 February 2017, 09:55:11 HÁRSFALVI Levente
>     <publicmailbox@harsfalvi.net <mailto:publicmailbox@harsfalvi.net>>
>     wrote:
>     > On 2017-02-20 08:26, groepaz@gmx.net <mailto:groepaz@gmx.net> wrote:
>     > > On Monday 20 February 2017, 08:19:57 Gerrit Heitsch
>     > >
>     > > <gerrit@laosinh.s.bawue.de <mailto:gerrit@laosinh.s.bawue.de>>
>     wrote:
>     > >> On 02/19/2017 11:47 PM, HÁRSFALVI Levente wrote:
>     > >>> Another addendum: Marko once measured the luma levels of different
>     > >>> VIC-II chips in the same C64 motherboard,
>     > >>>
>     http://www.zimmers.net/anonftp/pub/cbm/documents/chipdata/656x-luminance
>     <http://www.zimmers.net/anonftp/pub/cbm/documents/chipdata/656x-luminance>
>     > >>> s.
>     > >>> txt>
>     > >>>
>     > >>>  . I don't know how well the data practically holds, since the
>     > >>>
>     > >>> measurements have been done without using a standard 75 ohm
>     load; yet,
>     > >>> one thing seems to be sure: there are slight differences between
>     > >>> different VIC-II chip revisions in the luma levels they
>     produce. Maybe
>     > >>> part of what I've seen has been a result of that. I can't
>     speak of the
>     > >>> other symptoms, I didn't make measurements myself.
>     > >>
>     > >> We have to remember that VIC is a bit of a mixed signal chip, it is
>     > >> mostly digital, but also produces analog signals. I take it as
>     a given
>     > >> that there will be slight differences between VICs of the same
>     revision,
>     > >> even if they come from the same wafer, let alone from different
>     > >> production runs where the process was tweaked over time.
>     > >>
>     > >> So measuring luma levels only counts if you have multiple VICs
>     of each
>     > >> revision you can compare against each other.
>     > >
>     > > indeed, some other ppl checked the luma levels in the past
>     decades, and
>     > > its
>     > > always slightly different :)
>     >
>     > The question here would be IMHO whether there is a correlation between
>     > VIC-II revision numbers and the luma maps the respective chips
>     produce.
>     > The rest (general phenomenon of output level variances of mixed signal
>     > chips, general statements about measurement variances due to people
>     > measuring video signals with different / generally inadequate
>     equipment
>     > etc. etc. etc.) is obvious.
>
>     unfortunately, to find that out... you'd have to check quite a few
>     chips. i
>     dont think the existing data is even remotely close to draw this kind of
>     conclusions.
>
>     --
>
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>
>     C makes it easy to shoot yourself in the foot; C++ makes it harder,
>     but when
>     you do it blows your whole leg off.
>     <Bjarne Stroustrup>
>
>
>
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