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Author Topic: Timing of shutter release and position of object  (Read 3168 times)
wlemann
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« on: November 27, 2005, 03:43:18 PM »
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I have noticed a perculiar effect when shooting an object moving across the frame at shutter speeds sufficient to stop the motion. It seems that the object (like a person walking) is less advanced across the frame than it appeared to be when I released the shutter. To be more specific. If a person is walking from left to right in my viewfinder, it seems that, if I release the shutter when it seems that the person is in the midpoint of the frame, the image will depict the person as significantly more to the left (the starting point) than I thought they would be. What is this about?
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Robert Spoecker
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« Reply #1 on: November 27, 2005, 04:12:53 PM »
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Shutter lag.

A shutter does not open exactly when the shutter button is pressed but some small time increment after.  This lag becomes less on more expensive cameras but there is always some.

Robert
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Tim Gray
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« Reply #2 on: November 27, 2005, 06:00:55 PM »
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I think the implication of the original poster was that the image appeared to be captured _before_ the shutter was pressed  
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Robert Spoecker
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« Reply #3 on: November 27, 2005, 08:01:08 PM »
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Tim,

I think you are right after re reading the original post but I guess my mind dismissed it as it seems possible that the camera does the actual image capture after the button is pushed but how can it possibly do it before and if it does how does it know when to expose. With a camera that does that you gotta hurry to take the camera out of the camera bag or it will take the exposure  in the dark of the bag lol.

Robert
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DarkPenguin
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« Reply #4 on: November 27, 2005, 08:32:20 PM »
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Seems like interpolation gone awry.  He should switch to foveon.
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jani
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« Reply #5 on: November 28, 2005, 06:24:12 AM »
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Quote
I think you are right after re reading the original post but I guess my mind dismissed it as it seems possible that the camera does the actual image capture after the button is pushed but how can it possibly do it before and if it does how does it know when to expose. With a camera that does that you gotta hurry to take the camera out of the camera bag or it will take the exposure  in the dark of the bag lol.
 

I had a similar experience when I first started using my 20D instead of the old PowerShot S40.

The reason is, as you suggested, shutter lag. Or rather, the lack of it.

With cameras that have shutter lag, you get accustomed to it, so that you think the image will be taken at a later time than it actually is on a proper camera.

This creates the mental illusion that the image was captured before you pressed the shutter.
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Jan
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« Reply #6 on: November 28, 2005, 06:28:54 AM »
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Or I might suggest a problem with the mirror or prism.  Either of these out of alignment just slightly could result in the image being displayed in the viewfinder different than it would on the chip (or film).

Kelly
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dazzajl
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« Reply #7 on: November 28, 2005, 07:58:28 AM »
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Or.....


if it's a camera with an electronic viewfinder, there could be a delay on the display that's greater than the lag on the shutter. OK, not the most likey reason but it's certainly possible.  
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wlemann
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« Reply #8 on: November 28, 2005, 04:33:34 PM »
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Appreciate all of your help and insights.

There is no question about what I am seeing.  I was at Pimlico track in Baltimore over the weekend and shooting the horses (not really) being trained.  I would see what appeared to me to be the horse in the center of the frame and when I viewed the image it was as I described.  

This is not the first time this has happened with this camera (1DsMkII) and with the 1Ds as well.

I hear the impossibility explanations loud and clear but this is what is happening.  I am compensatiing with moving subjects to have them nearly out of the frame to get them closer to the center of the frame.

Well there you have it.

Walter
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boku
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« Reply #9 on: November 28, 2005, 05:36:23 PM »
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Appreciate all of your help and insights.

There is no question about what I am seeing.  I was at Pimlico track in Baltimore over the weekend and shooting the horses (not really) being trained.  I would see what appeared to me to be the horse in the center of the frame and when I viewed the image it was as I described. 

This is not the first time this has happened with this camera (1DsMkII) and with the 1Ds as well.

I hear the impossibility explanations loud and clear but this is what is happening.  I am compensatiing with moving subjects to have them nearly out of the frame to get them closer to the center of the frame.

Well there you have it.

Walter

I sure hope they don't count on you for determining photo finishes!  
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Bob Kulon

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Play it Straight and Play it True, my Brother.
Tim Gray
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« Reply #10 on: November 28, 2005, 06:38:14 PM »
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try putting in machine gun mode (jpgs) and hold the shutter release while tracking - might give a clue.
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Paul Sumi
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« Reply #11 on: November 28, 2005, 06:50:13 PM »
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I am compensatiing with moving subjects to have them nearly out of the frame to get them closer to the center of the frame.
[a href=\"index.php?act=findpost&pid=52361\"][{POST_SNAPBACK}][/a]

I presume the horses are running from left to right, and that you press the shutter when they are in the center of the frame.

1) Are you panning the camera left to right as the horses run by?

2) Are you "following through" with the pan after you press the shutter?

If you are doing both of these things, the only way I can figure that the horses would end up on the left side of the frame is that you are panning at a faster rate than the horses are moving.  In the brief instant after you press the button and before the shutter releases, the camera continues to move to the right faster than the horses have.  This assumes the horses maintain a constant speed.

If you are panning, then stop panning when you press the shutter, then the horses should be right of center.

If you are panning at the same rate as the horses move and are following through at the same rate, then they should more or less be in the center when you press the shutter.

Paul
« Last Edit: November 28, 2005, 07:46:43 PM by PaulS » Logged

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