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Old Nov 29, 2004, 12:57 PM   #11
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george_ wrote:
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JimC how do you know what shutter speed / aperture / ISO did the camera use ?


Do you use any software that allows you to see?
Almost any decent image editor can show you the EXIF (a header in the image files containing information about the camera settings used). Virtually all modern digital cameras have this information (butsome editors strip out this information when you modify a photo).

Here's where you can download a free package that can see the EXIF:

http://www.irfanview.com (make sure to download the free plugins, too).

After opening an image (File, Open), go to Image, Information, EXIF to see the camera settings used.


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Old Nov 29, 2004, 1:12 PM   #12
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thanks
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Old Nov 29, 2004, 1:51 PM   #13
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1 question

Why did the 2 first pics ( 1220/1221 ) had shutter speeds 1/160 1/200 and the pic No 1229 has 1/1600 ? In the 1229 , as JimC says , you were not moving at all.At the first two you were moving and thats why the shutter speeds were lower ?..
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Old Nov 29, 2004, 2:05 PM   #14
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oh i misstyped the shutter speed of the picture no. 1229 , it was 1/600 and not 1/1600.
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Old Nov 29, 2004, 2:25 PM   #15
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george_ wrote:
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1 question

Why did the 2 first pics ( 1220/1221 ) had shutter speeds 1/160 1/200 and the pic No 1229 has 1/1600 ? In the 1229 , as JimC says , you were not moving at all.At the first two you were moving and thats why the shutter speeds were lower ?..
George, I didn't say anything about him moving... I'm not sure what you're referring to, unless it's this comment:

JimC wrote:
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The shutter speeds you're getting are well above the 1/focal length rule of thumb. So, the camera's autoexposure algorithms aren't going to boost the ISO speed to allow faster shutter speeds in these conditions (it doesn't know you're trying to freeze a moving vehicle).
img_1229.jpg has a shutter speed of 1/640 second (actually 1/636, but it's rounded to the nearest stop), at an Aperture of f/2.8, at ISO 50. It's using a faster shutter speed because he deliberately underexposed it by one stop, and the lighting level probably changed a little bit from the first photos (and more sky in the image can also cause the metering to use a faster shutter speed).

The shutter speed a camera canuse (and still get proper exposure) will depend on 3 things:

Aperture, ISO speed, and Lighting Levels.

He's already shooting wide open (maximum aperture of f/2.8 ), and he can't change the lighting levels. Now, some models have aperture priority (so that you can specify a larger aperture in some conditions). But, this would not have helped for his photos (the camera was already using the largest available aperture).

So, any other compact camera with a lens starting out at f/2.8, set to ISO 50 would have approximately the same shutter speeds as he's getting with his Canon. No magical sports modes, manual exposure, etc.,would havechanged that if you want properly exposed photos. A camera must keep the shutter open long enough to properly expose the image.

You can influence it with some things (i.e., using a higher ISO speed), and you can buy a camera with a brighter lens (i.e., larger available aperture). But, virtually all subcompact models have similar lens ratings (start out at f/2.8, and lose brightness as more zoom is used). That's why I referred you to this thread when I responded to one of your earlier threads a while back. It explains how these three factors (Aperture, Lighting, ISO speed) effect the shutter speeds you can achieve:

http://www.stevesforums.com/forums/v...amp;forum_id=2


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Old Nov 29, 2004, 2:55 PM   #16
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what do you mean with the term << by one stop >> ? "It's using a faster shutter speed because he deliberately underexposed it by one stop"

sorry if i become a bit tiring for you , i just cant find some answers in the glossary or in the forums.


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Old Nov 29, 2004, 3:09 PM   #17
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Yes, you can deliberately underexpose a photo by one stop (changing theaperture or shutter speed so that you're lettinghalf as much light in). In his case, he was doubling the shutter speed to accomplish this.

So, if you underexpose by one stop, you're using shutter speeds twice as fast as you would need for proper exposure (or using a smaller aperture to let half thelight in for the same shutter speed). I would not recommend this technique, unless no other option exists for reducing motion blur (you have already increased ISO Speed, and you are already at your maximum aperture). Because, you end up with an underexposed (darker) photo if you do it that way (deliberately underexposing a shot to get faster shutter speeds).

Again, read the thread I pointed you to for how Aperture, EV,ISO speed and shutter speed work together for proper exposure.

http://www.stevesforums.com/forums/v...amp;forum_id=2

You may also want to get a book on Basic Photography (it doesn't have to be digital, since the concepts are the same) so you'll get a better understanding of how exposure works.


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