A 35mm film camera represented in Python object

[D.M. Procida]

Eli the Bearded <*@eli.users.panix.com> wrote:

> In comp.lang.python,
> D.M. Procida <real-not-anti-spam-address at apple-juice.co.uk> wrote:
> > Eli the Bearded <*@eli.users.panix.com> wrote:
> >> I see you don't even attempt to tackle ISO outside of
> >> supported range (and I have no idea how the camera itself deals with
> >> that). Is the camera sensing the ISO from the film roll (so won't work
> >> with hand rolled film cartridges)? Is there a setting on the camera to
> >> manually specify that? (I don't think so.)
> > The camera's film speed setting (it's old enough that it's ASA rather
> > than ISO) is set manually. If you try to set an illegal value, there's a
> > setter decorator that raises a NonExistentFilmSpeed exception.
> 
> I can see what the code does, I'm asking what the camera does and do you
> plan to work that into your code? Maybe it only works for ISO 1600 in
> manual mode, but works.

The code does what the camera allows - the camera has a ring with film
speeds of 25, 50, 100, 200, 400, 800 marked on it; those are the values
you can select (in fact there are two unmarked steps in between each of
those, but I've yet to build those in).

Internally, moving the film speed ring slides contacts along a variable
resistor, which is part of the metering system circuitry. It could be
that the range of the resistor or the theoretical range of the circuit
is beyond the settable values, but I can't work that out from the
circuit diagram.

Daniele