Richard Ross wrote:
> It's likely that a spotmeter would use silicon blue cells, which have a
> similar response to the human eye.
Silicon cells need a strong filtering to conter there strong
red-infrared sensibility, hence the name silicon-blue-cell SBC. It´s
clear, that this filtering can not give them the same frequencial
response as the human eye.
BTW CCDs are also made from silicon and they are sensitive to IR too,
astrophotographer like them because of this characteristic.
> CdS cells tend to be more sensitive at
> the red end,
CdS are more sensitive to yellow (like the human eye) than to other
colors. Normaly there is no filtering required, but of course the
sensitivity of the cell is no perfect match to the one of the film or
your vissiual perception.
> which is why TTL meters based on CdS cells tend to underexpose
> b/w film through red and orange filters -
This happens also with SBC
> exacerbated by the film's
> *decreased* sensitivity at the red end.
And every film is a little bit different.
>They're also too slow to work
> usefully in a spotmeter.
Minoltas first spotmeter worked with CdS
Regards
Richard
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