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Difficult technical question on ISO & light



 
 
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  #1  
Old October 29th 04, 04:00 PM
Alan Browne
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Chris Brown wrote:

In article ,
Tom Phillips wrote:

Film can be exposed for hours. Try that with a digital sensor.
It simply one of the differences between these two imaging
mediums.



You really should avoid such pontifications unless you're absolutely certain
you're correct, as you aren't in this case. Canon's current DSLRs, to take
one example, manage perfectly hapilly with multi-hour exposures. The only
major problem is that holding the shutter open that long may drain the
battery.


The EOS 1v has a clever shutter mechanism that holds the shutter open with
virtually no battery drain. I don't know if they've incorporated this into to
the 10D/20D or into the higher end cameras.

You can always use a grip with AA or rechargeable batteries in it for long
exposures.

Cheers,
Alan

--
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--
  #2  
Old October 29th 04, 04:03 PM
Alan Browne
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Tom Phillips wrote:

The ability of the canon EOS to do astrophotography is
in part due to the employment of a larger pixel. Larger
pixels mean a better signal and less noise, *but* (also


Further, CMOS (Canon) is less prone to heating over long exposures than CCD
based cameras.



--
-- rec.photo.equipment.35mm user resource:
-- http://www.aliasimages.com/rpe35mmur.htm
-- e-meil: there's no such thing as a FreeLunch.--
  #3  
Old October 30th 04, 04:19 PM
David J Taylor
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Gymmy Bob wrote:
[]
Bits and bytes are not involved in this thread previously. Only
pixels vs. grain of film. How we represent a pixel is another matter.


Aren't film grains "bits" in the sens that they can be either on or off?

Cheers,
David


  #4  
Old October 30th 04, 04:21 PM
David J Taylor
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John wrote:
[]
Nope. The human eye is an analog mechanism. Photography is an
effort to capture what the eyes can see in a relatively permanent
medium. Digital is an effort to make money. Digital images are not
analog nor are they permanent. It follows that digital is NOT
photography.


The eye has a digital connection to the brain....

David


  #6  
Old October 31st 04, 05:46 PM
jpc
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On Sun, 31 Oct 2004 11:28:29 GMT, Chris Brown
wrote:

In article ,
Chris Brown wrote:
In article ,
Tom Phillips wrote:

Show me a "multi hour" digital exposure.


OK, I'll take one tonight and upload it. Have to be of something indoors and
boring, I'm afraid, as there's too much light pollution where I live to do
such a long exposure outside, and the weather's pretty nasty atm as well.


OK, I must admit, I'm having trouble with this. Anyone have any suggestions
for a light source that will result in a decent exposure over a couple of
hours, that I can easilly set up in an otherwise pitch-black room, and that
won't result in either no image being recorded, or massive overexposure, at
any sensible aperture?



1--a low wattage incandescent with a lot of neutral density filtering.
If you can find a metalized mylar gift bag--I got mine at the local
liquor store-- two or three thickess should cut the light down by
10000X or more.

2 a black light bulb with less filtering. This may blow out the blue
channel but the green and red channel might turn out interesting.

3--your light poluted night sky after you raise the blind a couple
inches

4---an old floppy disk taped over the camera lens plus your light
poluted night sky. This is supposed to act as an infrared filter

5--something with a lcd placed in a box with a pin hole opening poked
in the box.

This is just a few suggestions that popped into my mind.

jpc

  #7  
Old October 31st 04, 07:34 PM
Marvin Margoshes
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"David J Taylor" wrote in message
...
Gymmy Bob wrote:
[]
Bits and bytes are not involved in this thread previously. Only
pixels vs. grain of film. How we represent a pixel is another matter.


Aren't film grains "bits" in the sens that they can be either on or off?


Yes. And when measurements are made of small areas of the film, one is
essentilaly counting grains of silver. It is the main noise source in that
type of measurement.


Cheers,
David



  #8  
Old October 31st 04, 08:19 PM
David J Taylor
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Marvin Margoshes wrote:
"David J Taylor" wrote in message

[]
Aren't film grains "bits" in the sens that they can be either on or
off?


Yes. And when measurements are made of small areas of the film, one
is essentilaly counting grains of silver. It is the main noise
source in that type of measurement.


Thanks for confirming that.

David


  #9  
Old October 31st 04, 08:47 PM
David J. Littleboy
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"David J Taylor" wrote in message
...
Marvin Margoshes wrote:
"David J Taylor" wrote in message

[]
Aren't film grains "bits" in the sens that they can be either on or
off?


Yes. And when measurements are made of small areas of the film, one
is essentilaly counting grains of silver. It is the main noise
source in that type of measurement.


Thanks for confirming that.


There's a page on the Kodak site (sorry, I don't have the link) that claims
that what we perceive as grain is statistical variations in the distribution
of the grains. I.e. that the grains themselves are _much_ smaller than the
frequency of the grain noise perceived.

David J. Littleboy
Tokyo, Japan


  #10  
Old November 2nd 04, 07:32 AM
David J Taylor
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Default Difficult technical question on ISO & light

Gregory W Blank wrote:
In article ,
Christopher Woodhouse wrote:

For fine art work I am
assuming that the eye can resolve 1 minute of arc (as a guideline)
and my research was an exploration of the limits of digital cameras
vs scanning primarily MF film.


1 minute at 10 feet, 100 feet or 1000 ? ;-)


Distance is irrelevant if an angular measure is quoted.

David


 




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