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Old Apr 19, 2005, 4:40 PM   #1
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I am working in the EOS Viewer Utilityand thoroughly confused by the info displayed in the Histiogram. Main confusion, it shows the ISO Speed as 1600 everytime I take a picture in any mode(I am in Manual now for a class assignment) yet the ISO shutter speed displayed is what I set it to to take the picture. What am I being told? In the Metadata all it shows is the ISO Speed at 1600. This is extremely confusing. Please someone set me straight.:?
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Old Apr 19, 2005, 7:03 PM   #2
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You're getting me confused, we'll see if I understand your problem. ISO speed and shutter speed are two different things. ISO speed is a measure of how sensitive the film, or sensor, is to light. The higher the number the more sensitive it is but the more noise you will get in the image.

Shutter speed is a measure of how long the film, or sensor, is exposed to light. So a shutter speed of 1000 means the sensor is exposed to light for 1/1000th of a second.

Example: if you have your camera set to an ISO of 100 the sensor will need more exposure time because it's not that sensitive to light, so the camera will conpensate by using a slower shutter speed, to keep the shutter open longer, in a low light condition. So to keep things like motion blur and the like from happening what you would do is increase the ISO on the camera so it doesn't need to expose the sensor to light as long; thus giving you a faster shutter speed which will help minimize motion blur, at the trade off of more noise in your pictures.


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Old Apr 19, 2005, 7:21 PM   #3
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You have to set the ISO speed in any of the creative modes and manual is one of them. One of my pet peeves about the 20D is that the ISO does not stay on the top LCD screen after being set and it is easy to forget where you are. One way I have found is to check the info screen before shooting in any particular location and just check the lower right corner for the ISO. ISO is set automatically in the basic modes from 100 to 400 I believe but has to be set manually elsewhere.

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Old Apr 20, 2005, 6:31 AM   #4
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Didn't mean to confuse anyone but now you see what I found....I understand all the concepts you mention. On the Canon 20D in The Metadata displayed and the Histogram it states that the ISO Setting Range=1600 but lists the shutter speed at whatever I set it or what the AE is. My understanding was that the ISO# is the shutter speed. That is why if I want to change my shutter/ISO sensitivity I press the ISO button and scroll to the shutter speed I desire. When reviewing the Metadata and/or Histogram it states the ISO Setting range at 1600 for ALL shutter speeds yet lists the ISO/shuttter speed I selected for that particular picture. Could it be that this is just the all inclusive range of the 20D without changing this to 3200?
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Old Apr 20, 2005, 7:52 AM   #5
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The ISO and the shutter speed are set independantly with different buttons. Push the ISO button on the top of the camera and then turn the dial on the back of the camera to change the ISO. You have to be in Creative Mode.
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Old Apr 20, 2005, 8:11 AM   #6
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mdbassman wrote:
Quote:
My understanding was that the ISO# is the shutter speed.
I'm afraid you've misunderstood.

There are 3 ways to control your exposure.
1. Aperture
2. Shutter Speed
3. ISO sensitivity

These are 3 different things with different settings on the camera. You seem to be mixing up #2 & #3.

When you use a film camera the ISO is a property of the film, when using a digital camera you can think of it a bit like a gain (or volume if you prefer) control on the sensor. It is completely independent of the shutter speed.

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Old Apr 20, 2005, 8:58 AM   #7
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mdbassman

Check out the Basics

-> especially here
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Old Apr 20, 2005, 5:27 PM   #8
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Thank you gentlemen both!! I am still a bit in the "film" mode.
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Old Apr 21, 2005, 8:39 AM   #9
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NHL!! Many Thanks! This was immensly helpful!!!
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Old Apr 21, 2005, 9:04 AM   #10
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NHL! You don't happen to know a discussion on ISO v. Shutter Speed as in depth as your Ap v. Tv? Aperature v. shutter
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