Weird Focus

artyman

artyman

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Ken
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Yesterday I thought I'd try the 8fps capability of the 7D it ran off 20 shots before it slowed, which seems fine for what I want. It did however throw up one anomaly in the middle of the sequence. I was shooting AI Servo obviously with a moving target, single point expansion. All focussed OK except this one shot. Now the odd thing is the destination display is in better focus than the centre where the number plate appears to show a bit of vertical movement. How is it possible for the top of the frame not to show this movement but it does further down.

Answers on a postcard :lol:

1/60 f6.3 ISO 1600
http://SPAM/c3whur/mar/Img_2114.jpg

http://SPAM/c3whur/mar/Img_2114Centre.jpg

http://SPAM/c3whur/mar/Img_2114Top.jpg
 
Hi Ken,

I'm not an expert, as you can tell I've hardly posted, but it could be that the screen flickers like a TV ie so many frames per second. So the camera only picked up one of these frames and wouldn't show any motion as for the rest of the exposure the screen was not showing anything. Would only be 10ths of a second but would explain it.
 
Yep, I think Alex has got it in one.
 
alexk1985 said:
Hi Ken,

I'm not an expert, as you can tell I've hardly posted, but it could be that the screen flickers like a TV ie so many frames per second. So the camera only picked up one of these frames and wouldn't show any motion as for the rest of the exposure the screen was not showing anything. Would only be 10ths of a second but would explain it.
Click to expand...

:thumbs: I agree
 
I agree as well. To support this I took a picture of a bus once in Sweden and it only showed part of the display despite me seeing the full area. In this case my shutter speed must have been faster than the display rate on the bus.
 
I don't think it is display screen flicker that is the reason as the trim line jut under it does not show any indication of movement.
 
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