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Main
Date: 25 Oct 2006 15:39:32
From: Mike
Subject: Converting digital cameras
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I know that it is a common practice to convert webcams for astro use, but
what about
doing the same to a cheap 6 MP point-and-shoot camera? Is there the
possibility of
doing that? I haven't seen anything that suggests that it is possible.
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Date: 25 Oct 2006 10:39:20
From: Greg Crinklaw
Subject: Re: Converting digital cameras
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Mike wrote:
> I know that it is a common practice to convert webcams for astro use,
> but what about doing the same to a cheap 6 MP point-and-shoot camera?
> Is there the possibility of doing that? I haven't seen anything that
> suggests that it is possible.
The advantage of a web cam is that, being a video camera, it can take
large numbers of frames quickly. The poor ones with badd seeing can be
culled and then the remaining frames stacked, which greatly improves the
signal to noise (and makes a very nice image).
Obviously, a point-and-shoot camera won't have this advantage unless you
can use it to take movies. But even then, you will be limited by the
memory space.
Greg
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
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Date: 25 Oct 2006 16:53:28
From: Mike
Subject: Re: Converting digital cameras
|
"Greg Crinklaw" <theskyhoundyoureye@yahoo.com > wrote in message
news:97bdd$453f9330$4212a52c$1099@TULAROSA.NET...
> Mike wrote:
>> I know that it is a common practice to convert webcams for astro use,
>> but what about doing the same to a cheap 6 MP point-and-shoot camera?
>> Is there the possibility of doing that? I haven't seen anything that
>> suggests that it is possible.
>
> The advantage of a web cam is that, being a video camera, it can take
> large numbers of frames quickly. The poor ones with badd seeing can be
> culled and then the remaining frames stacked, which greatly improves the
> signal to noise (and makes a very nice image).
>
> Obviously, a point-and-shoot camera won't have this advantage unless you
> can use it to take movies. But even then, you will be limited by the
> memory space.
>
But, the idea here is to make the illogical logical.
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Date: 25 Oct 2006 12:18:14
From: Greg Crinklaw
Subject: Re: Converting digital cameras
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Mike wrote:
> "Greg Crinklaw" <theskyhoundyoureye@yahoo.com> wrote in message
> news:97bdd$453f9330$4212a52c$1099@TULAROSA.NET...
>> Mike wrote:
>>> I know that it is a common practice to convert webcams for astro use,
>>> but what about doing the same to a cheap 6 MP point-and-shoot camera?
>>> Is there the possibility of doing that? I haven't seen anything that
>>> suggests that it is possible.
>> The advantage of a web cam is that, being a video camera, it can take
>> large numbers of frames quickly. The poor ones with badd seeing can be
>> culled and then the remaining frames stacked, which greatly improves the
>> signal to noise (and makes a very nice image).
>>
>> Obviously, a point-and-shoot camera won't have this advantage unless you
>> can use it to take movies. But even then, you will be limited by the
>> memory space.
>
> But, the idea here is to make the illogical logical.
Whatever. In most cases people are looking for an end result that is
useful in some way...
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
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Date: 25 Oct 2006 18:26:12
From: Mike
Subject: Re: Converting digital cameras
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>>> Obviously, a point-and-shoot camera won't have this advantage unless you
>>> can use it to take movies. But even then, you will be limited by the
>>> memory space.
Not really. The average memory card is at least 1 GB. Most AVI movies for
such a purpose
are maybe 20 - 100 MB...no?
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Date: 25 Oct 2006 12:58:04
From: Greg Crinklaw
Subject: Re: Converting digital cameras
|
Mike wrote:
>>>> Obviously, a point-and-shoot camera won't have this advantage unless you
>>>> can use it to take movies. But even then, you will be limited by the
>>>> memory space.
>
>
> Not really. The average memory card is at least 1 GB. Most AVI movies for
> such a purpose
> are maybe 20 - 100 MB...no?
I thought you wanted some advice. Silly me.
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
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Date: 25 Oct 2006 19:51:14
From: Mike
Subject: Re: Converting digital cameras
|
Maybe the problem with digicams is the ISO ratings. I would like to
know how they vary the ISO ratings. Also, if one is rated at ISO 400,
does that mean the CCD sensor is built for some ISO rating?
How does ISO rating even happen with CCD's? What is the ISO
of a webcam CCD?
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Date: 25 Oct 2006 14:36:18
From: Greg Crinklaw
Subject: Re: Converting digital cameras
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Mike wrote:
> Maybe the problem with digicams is the ISO ratings. I would like to
> know how they vary the ISO ratings. Also, if one is rated at ISO 400,
> does that mean the CCD sensor is built for some ISO rating?
>
> How does ISO rating even happen with CCD's? What is the ISO
> of a webcam CCD?
There's no such thing as ISO for a CCD. A CCD responds in a linear
fashion to the intensity of light striking it over some amount of time.
So it is natural for long exposures. BUT, over time it also
accumulates thermal noise. At anything near room temperature the
thermal noise ruins long exposures. The solution for most astronomical
CCDs is to cool them, lowering the thermal noise. Another solution is
to take many short exposures and stack them.
A consumer camera is not generally cooled sufficiently for long
exposures to be useful. Not only that, but such a camera is not just a
CCD; it's an involved processing process designed to take color pictures
in daylight. This process is a hindrance for most astronomical
applications.
I suggest you find a good book about astronomical imaging.
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
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Date: 25 Oct 2006 22:08:41
From: Mike
Subject: Re: Converting digital cameras
|
>
> There's no such thing as ISO for a CCD. A CCD responds in a linear
> fashion to the intensity of light striking it over some amount of time.
What do you mean? All digital cameras have the ability to change ISO
settings.
Mine is 80-800 and it's a Canon A540. Lord knows I wouldn't dream of
sacrificing this
but a cheap 4 or 5 MP point-and-shoot can be had for 50 to 100 bucks these
days.
So, as per my original question , is ISO settings done with software in the
camera or is the CCD
made in such a way that say 200 or 400 ISO is how it is built in?
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Date: 25 Oct 2006 18:45:11
From: Stephen Paul
Subject: Re: Converting digital cameras
|
Mike wrote:
>
> So, as per my original question , is ISO settings done with software in the
> camera or is the CCD
> made in such a way that say 200 or 400 ISO is how it is built in?
>
>
It's been a while since I studied electronics, but I'm going to take a
wild ass guess that the CMOS/CCD sensor is set with a higher charge bias
for higher ISO settings in order to decrease the amount of photon charge
that is required to saturate the pixel. Thus, the pixel saturates faster.
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Date: 25 Oct 2006 16:44:16
From: Greg Crinklaw
Subject: Re: Converting digital cameras
|
Mike wrote:
>> There's no such thing as ISO for a CCD. A CCD responds in a linear
>> fashion to the intensity of light striking it over some amount of time.
>
> What do you mean? All digital cameras have the ability to change ISO
> settings.
> Mine is 80-800 and it's a Canon A540. Lord knows I wouldn't dream of
> sacrificing this
> but a cheap 4 or 5 MP point-and-shoot can be had for 50 to 100 bucks these
> days.
>
> So, as per my original question , is ISO settings done with software in the
> camera or is the CCD
> made in such a way that say 200 or 400 ISO is how it is built in?
As I already answered that, I'm not about to repeat myself. If you are
interested in these things there are books as well as resources on the
web that you should be reading instead of asking question after question
here (and not particularly listening to what's being said).
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
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Date: 26 Oct 2006 00:01:14
From: Mike
Subject: Re: Converting digital cameras
|
"Greg Crinklaw" <theskyhoundyoureye@yahoo.com > wrote in message
news:47c79$453fe8b8$4212a52c$25221@TULAROSA.NET...
> Mike wrote:
>>> There's no such thing as ISO for a CCD. A CCD responds in a linear
>>> fashion to the intensity of light striking it over some amount of time.
>>
>> What do you mean? All digital cameras have the ability to change ISO
>> settings.
>> Mine is 80-800 and it's a Canon A540. Lord knows I wouldn't dream of
>> sacrificing this
>> but a cheap 4 or 5 MP point-and-shoot can be had for 50 to 100 bucks
>> these days.
>>
>> So, as per my original question , is ISO settings done with software in
>> the camera or is the CCD
>> made in such a way that say 200 or 400 ISO is how it is built in?
>
> As I already answered that, I'm not about to repeat myself. If you are
> interested in these things there are books as well as resources on the web
> that you should be reading instead of asking question after question here
> (and not particularly listening to what's being said).
You just don't know. I wish you'd be honest and say so...ASSHOLE
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Date: 25 Oct 2006 18:57:12
From: Greg Crinklaw
Subject: Re: Converting digital cameras
|
Mike wrote:
> "Greg Crinklaw" <theskyhoundyoureye@yahoo.com> wrote in message
> news:47c79$453fe8b8$4212a52c$25221@TULAROSA.NET...
>> Mike wrote:
>>>> There's no such thing as ISO for a CCD. A CCD responds in a linear
>>>> fashion to the intensity of light striking it over some amount of time.
>>> What do you mean? All digital cameras have the ability to change ISO
>>> settings.
>>> Mine is 80-800 and it's a Canon A540. Lord knows I wouldn't dream of
>>> sacrificing this
>>> but a cheap 4 or 5 MP point-and-shoot can be had for 50 to 100 bucks
>>> these days.
>>>
>>> So, as per my original question , is ISO settings done with software in
>>> the camera or is the CCD
>>> made in such a way that say 200 or 400 ISO is how it is built in?
>> As I already answered that, I'm not about to repeat myself. If you are
>> interested in these things there are books as well as resources on the web
>> that you should be reading instead of asking question after question here
>> (and not particularly listening to what's being said).
>
> You just don't know. I wish you'd be honest and say so...ASSHOLE
Thanks for making it clear what I suspected all along. I did have some
doubt, but you laid that to rest rather succinctly. We both know who's
really being the asshole here don't we?
Don't you have anything better to do than yank the chains of people who
thought they could help out a little around here? YOU and YOUR KIND
(trolls--or assholes who are more interested in beating their chests
than learning something--take your pick) are why only a tiny handful of
people are willing to answer questions on this forum anymore.
*PLONK*
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
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Date: 26 Oct 2006 09:31:49
From: Roger Hamlett
Subject: Re: Converting digital cameras
|
"Mike" <NOSPAM@thankyamam.com > wrote in message
news:JfR%g.71820$E67.63449@clgrps13...
>
>>
>> There's no such thing as ISO for a CCD. A CCD responds in a linear
>> fashion to the intensity of light striking it over some amount of time.
>
> What do you mean? All digital cameras have the ability to change ISO
> settings.
> Mine is 80-800 and it's a Canon A540. Lord knows I wouldn't dream of
> sacrificing this
> but a cheap 4 or 5 MP point-and-shoot can be had for 50 to 100 bucks
> these days.
>
> So, as per my original question , is ISO settings done with software in
> the camera or is the CCD
> made in such a way that say 200 or 400 ISO is how it is built in?
These settings are 'artificial'. Basically, they are settings where the
amplifier gain is adjusted, so that for the same exposure/lens aperture as
the 'equivalent' film, full exposure, occurs at about the same light
intensity.
The comparison is very 'weak' though. On conventional film, extremely
small signals actually ge 'missed' by the chemistry (reciprocity failure),
while large signals tend to get clipped in a non linear fashion as
saturation is approached. The CCD, is basically linear (except if an ABG
electrode is fitted which introduces a similar 'large signal' clipping
effect, but at the cost of linearity). The 'equivalent' ISO figure for a
CCD, in terms of how little light is needed to get any detectable signal,
is in excess of 10000!. However you then have the problems of thermal
noise (charge building inside the sensor capacitors, from the heat inside
the chip), quantisation error (the 'step' nature of the signal after ADC
conversion, and random noise in this conversion), etc. etc...
Best Wishes
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Date: 26 Oct 2006 13:13:41
From: Paul Schlyter
Subject: Re: Converting digital cameras
|
In article <9g%%g.4755$RR2.4221@newsfe2-win.ntli.net >,
Roger Hamlett <rogerspamignored@ttelmah.demon.co.uk > wrote:
>
>"Mike" <NOSPAM@thankyamam.com> wrote in message
>news:JfR%g.71820$E67.63449@clgrps13...
>>
>>>
>>> There's no such thing as ISO for a CCD. A CCD responds in a linear
>>> fashion to the intensity of light striking it over some amount of time.
>>
>> What do you mean? All digital cameras have the ability to change ISO
>> settings.
>> Mine is 80-800 and it's a Canon A540. Lord knows I wouldn't dream of
>> sacrificing this
>> but a cheap 4 or 5 MP point-and-shoot can be had for 50 to 100 bucks
>> these days.
>>
>> So, as per my original question , is ISO settings done with software in
>> the camera or is the CCD
>> made in such a way that say 200 or 400 ISO is how it is built in?
>These settings are 'artificial'. Basically, they are settings where the
>amplifier gain is adjusted, so that for the same exposure/lens aperture as
>the 'equivalent' film, full exposure, occurs at about the same light
>intensity.
>The comparison is very 'weak' though. On conventional film, extremely
>small signals actually ge 'missed' by the chemistry (reciprocity failure),
>while large signals tend to get clipped in a non linear fashion as
>saturation is approached. The CCD, is basically linear (except if an ABG
>electrode is fitted which introduces a similar 'large signal' clipping
>effect, but at the cost of linearity). The 'equivalent' ISO figure for a
>CCD, in terms of how little light is needed to get any detectable signal,
>is in excess of 10000!. However you then have the problems of thermal
>noise (charge building inside the sensor capacitors, from the heat inside
>the chip), quantisation error (the 'step' nature of the signal after ADC
>conversion, and random noise in this conversion), etc. etc...
>
>Best Wishes
The definition for ISO film speed is (picked from
http://en.wikipedia.org/wiki/Film_speed#ISO_film_speed_scales ):
# Film speed is found by referencing the Hurter-Driffield curve, or D-log E
# curve, for the film. This is a plot of optical density vs. log of exposure
# (lux-seconds). There are typically five regions in the curve: the base + fog,
# the toe, the linear region, the shoulder, and the overexposed region.
# Following the curve to the point where density exceeds the base + fog by 0.1,
# find the corresponding exposure. Dividing 0.8 by that exposure yields the
# linear ISO speed rating.
The optical density 0.1 corresponds to an absorption of approx. 10% of the
incident light by the film. A reasonable corresponding definition for
a CCD chip is to illuminate it until the level becomes 10% of the
saturation level, and then divide 0.8 by the number of lux-seconds
required to obtain the ISO speed of the CCD chip.
> On conventional film, extremely small signals actually get 'missed' by
> the chemistry (reciprocity failure).
Yes -- and one way to view that is that on conventional film, the ISO
speed drops at very low light levels. CCD chips has no corresponding
reciprocity failure.
--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/
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Date: 26 Oct 2006 12:48:40
From: Mike
Subject: Re: Converting digital cameras
|
"Roger Hamlett" <rogerspamignored@ttelmah.demon.co.uk > wrote in message
news:9g%%g.4755$RR2.4221@newsfe2-win.ntli.net...
>
> "Mike" <NOSPAM@thankyamam.com> wrote in message
> news:JfR%g.71820$E67.63449@clgrps13...
>>
>>>
>>> There's no such thing as ISO for a CCD. A CCD responds in a linear
>>> fashion to the intensity of light striking it over some amount of time.
>>
>> What do you mean? All digital cameras have the ability to change ISO
>> settings.
>> Mine is 80-800 and it's a Canon A540. Lord knows I wouldn't dream of
>> sacrificing this
>> but a cheap 4 or 5 MP point-and-shoot can be had for 50 to 100 bucks
>> these days.
>>
>> So, as per my original question , is ISO settings done with software in
>> the camera or is the CCD
>> made in such a way that say 200 or 400 ISO is how it is built in?
> These settings are 'artificial'. Basically, they are settings where the
> amplifier gain is adjusted, so that for the same exposure/lens aperture as
> the 'equivalent' film, full exposure, occurs at about the same light
> intensity.
> The comparison is very 'weak' though. On conventional film, extremely
> small signals actually ge 'missed' by the chemistry (reciprocity failure),
> while large signals tend to get clipped in a non linear fashion as
> saturation is approached. The CCD, is basically linear (except if an ABG
> electrode is fitted which introduces a similar 'large signal' clipping
> effect, but at the cost of linearity). The 'equivalent' ISO figure for a
> CCD, in terms of how little light is needed to get any detectable signal,
> is in excess of 10000!. However you then have the problems of thermal
> noise (charge building inside the sensor capacitors, from the heat inside
> the chip), quantisation error (the 'step' nature of the signal after ADC
> conversion, and random noise in this conversion), etc. etc...
>
> Best Wishes
Thanks for the definitive answer.
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| |
Date: 25 Oct 2006 09:27:39
From: laura halliday
Subject: Re: Converting digital cameras
|
Mike wrote:
> I know that it is a common practice to convert webcams for astro use, but
> what about
> doing the same to a cheap 6 MP point-and-shoot camera? Is there the
> possibility of
> doing that? I haven't seen anything that suggests that it is possible.
You can do anything you want. However, the point and shoot
cameras are highly automated, and may be more trouble than
they are worth to get them to do astronomically useful things.
Focusing and exposure could both be a challenge.
Why not try it and see? My first attempt in this area was
bolting the guts of a web camera to the focal plane of a
junk 35mm film camera. It worked fine. I have another
camera that is the innards of a QuickCam Fusion mounted
in a little box, with the business end of a T ring epoxied to
the front. It too works fine.
Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte
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Date: 25 Oct 2006 16:57:07
From: Mike
Subject: Re: Converting digital cameras
|
>
> Why not try it and see? My first attempt in this area was
> bolting the guts of a web camera to the focal plane of a
> junk 35mm film camera.
Does the web camera innards in the 35mm SLR allowed to act for long
exposures? Do you
use it with the bulb setting for long exposures? Or does it continue to
work in movie?
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Date: 25 Oct 2006 16:16:36
From: laura halliday
Subject: Re: Converting digital cameras
|
Stephen Paul wrote:
> Mike wrote:
> >
> > So, as per my original question , is ISO settings done with software in the
> > camera or is the CCD
> > made in such a way that say 200 or 400 ISO is how it is built in?
> >
> >
>
> It's been a while since I studied electronics, but I'm going to take a
> wild ass guess that the CMOS/CCD sensor is set with a higher charge bias
> for higher ISO settings in order to decrease the amount of photon charge
> that is required to saturate the pixel. Thus, the pixel saturates faster.
No.
The value read out of each well is scaled by an analog amplifier
before being digitized to form the image. The amount of scaling
is calibrated to simulate the effect of film of different ISO speeds.
Nothing new here: nobody ever knew how film worked, either.
Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte
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Date: 25 Oct 2006 20:02:08
From: Stephen Paul
Subject: Re: Converting digital cameras
|
laura halliday wrote:
> The value read out of each well is scaled by an analog amplifier
> before being digitized to form the image. The amount of scaling
> is calibrated to simulate the effect of film of different ISO speeds.
Cool. Glad someone had a real answer.
Do I get any points for imagination?
:-)
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Date: 25 Oct 2006 18:59:06
From: Greg Crinklaw
Subject: Re: Converting digital cameras
|
Stephen Paul wrote:
> laura halliday wrote:
>
>> The value read out of each well is scaled by an analog amplifier
>> before being digitized to form the image. The amount of scaling
>> is calibrated to simulate the effect of film of different ISO speeds.
>
>
> Cool. Glad someone had a real answer.
Man, that's really obnoxious, Paul. Last time I bother to answer a
question around here. Never again!
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
|
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Date: 26 Oct 2006 03:10:39
From: Mike
Subject: Re: Converting digital cameras
|
"Greg Crinklaw" <theskyhoundyoureye@yahoo.com > wrote in message
news:e8ce6$45400850$4212a52c$2834@TULAROSA.NET...
> Stephen Paul wrote:
>> laura halliday wrote:
>>
>>> The value read out of each well is scaled by an analog amplifier
>>> before being digitized to form the image. The amount of scaling
>>> is calibrated to simulate the effect of film of different ISO speeds.
>>
>>
>> Cool. Glad someone had a real answer.
>
> Man, that's really obnoxious, Paul. Last time I bother to answer a
> question around here. Never again!
Ooooo..Greggy weggy feeling left out?
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Date: 25 Oct 2006 21:10:26
From: Stephen Paul
Subject: Re: Converting digital cameras
|
Greg Crinklaw wrote:
> Stephen Paul wrote:
>> laura halliday wrote:
>>
>>> The value read out of each well is scaled by an analog amplifier
>>> before being digitized to form the image. The amount of scaling
>>> is calibrated to simulate the effect of film of different ISO speeds.
>>
>>
>> Cool. Glad someone had a real answer.
>
> Man, that's really obnoxious, Paul. Last time I bother to answer a
> question around here. Never again!
>
Just to clarify, my comment was intentionally self deprecating. (I made
a swag, and it appears I was wrong.)
-Stephen
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Date: 25 Oct 2006 19:29:33
From: Greg Crinklaw
Subject: Re: Converting digital cameras
|
Stephen Paul wrote:
> Greg Crinklaw wrote:
>> Stephen Paul wrote:
>>> laura halliday wrote:
>>>
>>>> The value read out of each well is scaled by an analog amplifier
>>>> before being digitized to form the image. The amount of scaling
>>>> is calibrated to simulate the effect of film of different ISO speeds.
>>>
>>>
>>> Cool. Glad someone had a real answer.
>>
>> Man, that's really obnoxious, Paul. Last time I bother to answer a
>> question around here. Never again!
>>
>
> Just to clarify, my comment was intentionally self deprecating. (I made
> a swag, and it appears I was wrong.)
Sorry. I realize that now. I'm just ticked because I let this guy yank
my chain. I let myself be called an asshole for taking the time to try
to answer his ever-changing questions. I should know better, I guess.
--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)
SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html
To reply take out your eye
|
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Date: 26 Oct 2006 03:12:04
From: Mike
Subject: Re: Converting digital cameras
|
"Greg Crinklaw" <theskyhoundyoureye@yahoo.com > wrote in message
news:ed8$45400f37$4212a52c$20120@TULAROSA.NET...
> Stephen Paul wrote:
>> Greg Crinklaw wrote:
>>> Stephen Paul wrote:
>>>> laura halliday wrote:
>>>>
>>>>> The value read out of each well is scaled by an analog amplifier
>>>>> before being digitized to form the image. The amount of scaling
>>>>> is calibrated to simulate the effect of film of different ISO speeds.
>>>>
>>>>
>>>> Cool. Glad someone had a real answer.
>>>
>>> Man, that's really obnoxious, Paul. Last time I bother to answer a
>>> question around here. Never again!
>>>
>>
>> Just to clarify, my comment was intentionally self deprecating. (I made a
>> swag, and it appears I was wrong.)
>
> Sorry. I realize that now. I'm just ticked because I let this guy yank
> my chain. I let myself be called an asshole for taking the time to try to
> answer his ever-changing questions. I should know better, I guess.
You didn't do that at all. You snubbed me. Andrea was the big help here and
to a lesser extent
S.Paul.
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Date: 25 Oct 2006 21:57:43
From: Stephen Paul
Subject: Re: Converting digital cameras
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Greg Crinklaw wrote:
> Stephen Paul wrote:
>> Just to clarify, my comment was intentionally self deprecating. (I
>> made a swag, and it appears I was wrong.)
>
> Sorry. I realize that now.
No sweat.
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Date: 26 Oct 2006 00:08:32
From: Mike
Subject: Re: Converting digital cameras
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"Stephen Paul" <smarshallpaul@gmail.com > wrote in message
news:WJednQ_buoVnZ6LYnZ2dnUVZ_rSdnZ2d@comcast.com...
> laura halliday wrote:
>
>> The value read out of each well is scaled by an analog amplifier
>> before being digitized to form the image. The amount of scaling
>> is calibrated to simulate the effect of film of different ISO speeds.
>
In other words, the ISO standards are "built in" to the CCD in a way.
So, my guess is that a webcam CCD is only good for planetary and very little
for
star stuff due to the small signal/noise ratio of longer exposures required.
My guess is that
the avergae webcam CCD is perhaps ISO 100 or 200 tops.
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Date: 25 Oct 2006 13:24:26
From: laura halliday
Subject: Re: Converting digital cameras
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Mike wrote:
> >
> > Why not try it and see? My first attempt in this area was
> > bolting the guts of a web camera to the focal plane of a
> > junk 35mm film camera.
>
> Does the web camera innards in the 35mm SLR allowed to act for long
> exposures? Do you
> use it with the bulb setting for long exposures? Or does it continue to
> work in movie?
The web camera was the cheapest no-name POS camera
they had at the computer store. I actually bought a couple
of them, since some of the things I had in mind would void
the warranty. :-}
I didn't modify the camera electronically, so it remained
a web camera. What I got from the experiment was the
capability to use 35mm camera lenses, and to hook
the camera to a telescope with a T ring. There are better
ways to do these things (especially with the current crop
of DSLRs; I own a Digital Rebel), but I was curious...
If I wanted to use the camera I had to open the 35mm
shutter on B, then activate the web camera in software.
Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte
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Date: 26 Oct 2006 08:54:57
From: laura halliday
Subject: Re: Converting digital cameras
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Mike wrote:
> In other words, the ISO standards are "built in" to the CCD in a way.
>
> So, my guess is that a webcam CCD is only good for planetary and very little
> for
> star stuff due to the small signal/noise ratio of longer exposures required.
> My guess is that
> the avergae webcam CCD is perhaps ISO 100 or 200 tops.
People use webcams for lunar and planetary imaging, with
spectacular results. This is nothing new: I first tried it with
a Vesta Pro on Mars at the 2003 opposition. It was well-
established then.
You can modify webcams for long exposures, and you can
cool them, but I'm personally dubious about the value of
doing so. YMMV.
Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte
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