Prop stop

Joined
Jun 22, 2006
Messages
1,105
Location
Soldotna
Not sure where to put this but here seems reasonable.

These images were shot with my iPhone. Anyone out there who can explain to me the phenomenon of the prop being distorted and showing double the number of blades one would expect to see.

In a video of the prop, the blades actually fade off in pieces as they rotate. WEIRD.

Thanks for you help.

Both shots at ISO80, about 1/3000th

IMG_2239.jpg
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IMG_2255.jpg
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Joined
Jan 18, 2008
Messages
2,493
Location
Denmark
I think the iPhone is capable of taking two exposures in rapid succession, exposing for highlight or shadows and combining into one image. That would explain the extra blades. Will have to check if this is correct.
 
Joined
Jun 22, 2006
Messages
1,105
Location
Soldotna
Thanks, Tom. The iPhone does have an HDR setting but it was not turned on for this shot.

I am uploading a video to mobileme.com Will post later.

Thanks again.
 
Joined
Jul 16, 2009
Messages
10,094
Location
Newcastle
It would seem that the iPhone doesn't expose the whole sensor in a single instant but as a set of two or more moving 'slits' in an electronic implementation of the focal plane shutter. Presumably Apple know the exact details...
 
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