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How does ISO setting work?



 
 
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  #11  
Old July 16th 05, 03:03 PM
Don Stauffer
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David Arnstein wrote:
The digital cameras that I have seen have a feature that allows the
user to choose an ISO setting. I would like to know what this feature
does, since I suspect that it is useless.

My concern is that setting a high ISO number simply
1. Causes the camera to take pictures that are quite dark
2. Post processes the picture by increasing the brightness, in
software.

If this is the case, then I prefer to increase the brightness myself,
in Photoshop.

On the other hand, if the ISO adjustment on the camera actually
changes the physical properties of the photosensor, then it's a
different story.

I'd like some feedback on this before I spend my time experimenting
with different ISO settings.


The ISO setting is one parameter the exposure computer uses to determine
exposure (shutter speed and aperture [lens opening]). The default value
should give you the best balanced exposure. There IS now a definition
of the ISO exposure for digital cameras, but I can't find it right now.

You can push a digicam just as you can push a film camera by dialing in
a higher ISO value, which causes a smaller exposure (less energy) than
for the nominal value. This either shortens shutter speed, reduces
aperture, or both, depending on the exposure 'mode' you are using.
  #12  
Old July 16th 05, 03:12 PM
Don Stauffer
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Andy Sullivan wrote:


I look forward to your response Mr. Vuori.



I think Matti's post equates to, "I'm not using a decent
news reader and don't know how Usenet works."




Gee, while I was not the originator of the comment, I guess I myself do
not know how to set up my reader so that it doesn't show up cross posts.
I use Thunderbird. What do I have to do to keep from downloading and
seeing cross posts between rpd and rpe35?
  #13  
Old July 16th 05, 03:16 PM
Don Stauffer
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Ron Hunter wrote:

Vastly oversimplified:
The ISO number is like an amplifier volume setting. The larger the
number the 'louder' the light output from the sensor. And, like a sound
amplifier, excessive settings often produce very distorted, and
'clipped' output. The lower the ISO setting, the more light you need
for a usable picture, but the higher the setting, the more the output
from the sensor is amplified, and the more 'noise', and 'distortion' you
will see. Many cameras use software to improve the image quality, and,
since they have access to the original output from the sensor, they can
usually do this better than Photoshop.



I guess I'd argue with this. The sensor (the CCD chip) has the same
output regardless of the amplifier gain. If we push by using a higher
ISO setting, which results in less exposure, there will be fewer
photoelectrons in each well, and the CCD readout signal will be lower.
One can amplify signal AFTER the readout, but the sensor output is lower
when pushing exposure.
  #14  
Old July 16th 05, 07:56 PM
Paul Mitchum
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Don Stauffer wrote:

Andy Sullivan wrote:

[..]
I think Matti's post equates to, "I'm not using a decent
news reader and don't know how Usenet works."


Gee, while I was not the originator of the comment, I guess I myself do
not know how to set up my reader so that it doesn't show up cross posts.
I use Thunderbird. What do I have to do to keep from downloading and
seeing cross posts between rpd and rpe35?


Typically, a newsreader will only download a crossposted article once.
This message, for instance, is crossposted to three newsgroups. See the
Newsgroups: line, count three. :-)

So it'll get downloaded once, and then show up listed in any of the
three groups. If you read this message (I hope you do..), then it will
be marked as read for all three newsgroups.

Your newsreader should work this way without changing any settings. If
it doesn't, get a new newsreader.

If I had reposted this message three times, one for each newsgroup, then
(assuming you read all three newsgroups) it would be downloaded three
times, and you'd have to read it three times.

This is why crossposting is preferred to reposting, and why spammers
prefer reposting to crossposting.
  #15  
Old July 16th 05, 10:51 PM
Boat
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"Don Stauffer" wrote in message
...
Andy Sullivan wrote:


I look forward to your response Mr. Vuori.



I think Matti's post equates to, "I'm not using a decent
news reader and don't know how Usenet works."




Gee, while I was not the originator of the comment, I guess I myself do
not know how to set up my reader so that it doesn't show up cross posts. I
use Thunderbird. What do I have to do to keep from downloading and seeing
cross posts between rpd and rpe35?


Gosh. Here's one instance where Outlook Express manages to meet
expectations. It correctly filters crossposts that are marked as already
read.

  #16  
Old July 17th 05, 09:39 AM
Eru Ilúvatar
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Matti Vuori whined:

Could you please post in one group only...


If you don't like cross-posting, simply set your kill
filter so you don't see those posts, hypocrite. Your whining
just increasing the damn noise level.
  #17  
Old July 17th 05, 04:33 PM
Neil Ellwood
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On Sat, 16 Jul 2005 09:12:18 -0500, Don Stauffer wrote:

Andy Sullivan wrote:


I look forward to your response Mr. Vuori.



I think Matti's post equates to, "I'm not using a decent
news reader and don't know how Usenet works."




Gee, while I was not the originator of the comment, I guess I myself do
not know how to set up my reader so that it doesn't show up cross posts.
I use Thunderbird. What do I have to do to keep from downloading and
seeing cross posts between rpd and rpe35?

Use Pan instead?
--
neil
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