Re: A 35mm film camera represented in Python object

[Eli the Bearded]

In comp.lang.python,
D.M. Procida  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.

> I have to add a button and winder lever to the camera object itself, I'm
> doing those things bit by bit.

Gotcha.

> Yes, it would be fun to allow it to "take a picture" of an image file,
> and process the result. Or ultimately built into a web application using
> somehting like https://anvil.works and have take a real picture with a
> user's webcam.

Yes, that sounds like good future work.

Elijah
--
bring light into the dark box
-- 
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Re: 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  wrote:
> > Hi everyone, I've created  -
> > a representation of a Canonet G-III QL17 in Python.
> > 
> > There's also documentation: .
> 
> This is interesting. Some feedback.
> 
> > It's a pure Python model of the physical sub-systems of a camera and
> > their interactions. So far it's at a fairly high level - I haven't yet
> > got down to the level of individual springs and levers yet.
> 
> There's a wealth of specifics for that camera above individual springs
> and levers. Notably how the light meter performs with different
> batteries and how it works with other films. This much is clear from
> just a few minutes research on the Canonet G-III QL17 (what a mouthful
> of a name).
> 
> I'm guessing you plan to deal light meter quirks because of the battery
> voltage setting. 

You're absolutely right. In fact, the camera is initialised with a
battery with a certain voltage, and eventually the voltage needs to make
a difference to the behaviour of the metering circuit. However I haven't
figured that out yet.

> 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.
 
> Film spoilage isn't boolean in real life. If I rewind most, but not all
> of the way, before I open the back, I've only ruined a few frames. If I
> open it in a lightproof camera bag, I can take the roll out without
> rewinding.

I was going to settle for having the exposed frames ruined, if the
camera is opened in an environment of sufficient luminosity.
 
> On this camera, there's no manual double exposure setting, right? So
> partial rewind would be the way to do that. But I can make double
> exposures with this code:
> 
> >>> c.shutter.trip()
> >>> c.shutter.cock()
> >>> c.shutter.trip()

That's true - but only because I haven't yet finished adding the camera
controls. In normal use, you would only interact with the camera
controls, whereas c.shutter.trip() and so on are interacting with the
internal mechanisms.

I have to add a button and winder lever to the camera object itself, I'm
doing those things bit by bit.
 
> Does a camera like the one you have modelled that actively stop you from
> using a ISO/shutter speed/F-stop that will vastly over- or under- expose
> things? Or is it just a warning light in the viewfinder?

In A mode (shutter-priority autoexposure) it will simply not allow the
shutter to be tripped if the exposure is not within range. In manual
mode, there are no constraints.

> A useful thing your camera-as-code model could provide, but doesn't, is
> some measure of how exposed each frame is. This will be a function of
> film speed, iris setting, cumulative exposure time from zero or more
> shutter openings, and scene luminosity. (You could extend this to
> include opened back over exposure conditions.)

Yes, it would be fun to allow it to "take a picture" of an image file,
and process the result. Or ultimately built into a web application using
somehting like https://anvil.works and have take a real picture with a
user's webcam.

Thanks for the interest!

Daniele
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: A 35mm film camera represented in Python object

[Eli the Bearded]

In comp.lang.python,
D.M. Procida  wrote:
> Hi everyone, I've created  -
> a representation of a Canonet G-III QL17 in Python.
> 
> There's also documentation: .

This is interesting. Some feedback.

> It's a pure Python model of the physical sub-systems of a camera and
> their interactions. So far it's at a fairly high level - I haven't yet
> got down to the level of individual springs and levers yet.

There's a wealth of specifics for that camera above individual springs
and levers. Notably how the light meter performs with different
batteries and how it works with other films. This much is clear from
just a few minutes research on the Canonet G-III QL17 (what a mouthful
of a name).

I'm guessing you plan to deal light meter quirks because of the battery
voltage setting. 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.)

> You can do things like advance the film, release the shutter, meter the
> scene with the built-in light meter (if the camera has a battery of
> course) and even spoil your film if you make the mistake of opening the
> back in daylight.

Film spoilage isn't boolean in real life. If I rewind most, but not all
of the way, before I open the back, I've only ruined a few frames. If I
open it in a lightproof camera bag, I can take the roll out without
rewinding.

(I've done such things with pin hole cameras.)

> But you can also do things that you shouldn't do, like opening the back
> of the camera in daylight with a partially-exposed roll of film inside -
> which will spoil the film::
> 
> >>> c.back.open()
> Opening back
> Resetting frame counter to 0
> 'Film is ruined'

If luminosity is set to zero, that could emulate the lightproof bag.
Frame by frame "film is ruined" might be a better choice for boolean.

On this camera, there's no manual double exposure setting, right? So
partial rewind would be the way to do that. But I can make double
exposures with this code:

>>> c.shutter.trip()
Shutter openening for 1/128 seconds
Shutter closes
Shutter uncocked
'Tripped'
>>> c.shutter.cock()
Cocking shutter
Cocked
'Cocked'
>>> c.shutter_speed = 1/512
>>> c.shutter.trip()
Shutter openening for 1/512 seconds
Shutter closes
Shutter uncocked
'Tripped'
>>>

In general, I never used simple cameras with light meters. Advanced SLR
or dumb cameras. My personal favorite film camera is a Universal Mercury
II, a half frame 35mm from mid 1940s with hot and cold shoes (intended
for flash and film meter attachments), bulb to 1/1000 shutter range,
mechanical exposure calculator on the back, and a dial for reminding you
what film you have in it.

Does a camera like the one you have modelled that actively stop you from
using a ISO/shutter speed/F-stop that will vastly over- or under- expose
things? Or is it just a warning light in the viewfinder?

Certainly my c.shutter.trip() calls give me no advice from the meter.

A useful thing your camera-as-code model could provide, but doesn't, is
some measure of how exposed each frame is. This will be a function of
film speed, iris setting, cumulative exposure time from zero or more
shutter openings, and scene luminosity. (You could extend this to
include opened back over exposure conditions.)

Elijah
--
can see how this might get integrated with an image generation tool
-- 
https://mail.python.org/mailman/listinfo/python-list

Re: A 35mm film camera represented in Python object

[D.M. Procida]

Robert Latest  wrote:

> D.M. Procida wrote:
> > Hi everyone, I've created  -
> > a representation of a Canonet G-III QL17 in Python.
> 
> [...]
> 
> > The Canonet G-III QL17 is one of my favourites. One of my reasons for
> > writing this code is to appreciate the intricate mechanical logic
> > embodied in the machine.
> 
> I love both photography with mechanical camears (The Nikon FE2 being my
> favorite) and programming. 

Yes, it's more fun to compute.

> So I absolutely love your project. Also I think its
> totally nuts. 

Thanks, I will take that as a compliment.

Daniele
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