[LRFlex] Re: eagles

on 2/21/05 11:55 AM, Dr. Elliot Puritz at drpuritz@xxxxxxxxxxxxx wrote:

> 
> Hi Doug:  Well, at the golf course today one of our members was using his
> Canon EOS 1D ( I think ) with a Canon 500 mm lens and a 1.5 extender.  The
> Eagles have two Eaglets in their nest which sits high in a Pine Tree about
> one quarter mile away. What was interesting was the auto focus feature that
> enabled him to capture the flight of the Eagles.  He told me that the lens
> and camera have  "predictive" auto focus so that the camera quickly "knows"
> where the subject is going to, and focuses there.  Rather amazing.
> 
> Elliot 
>

Predicting the flight of eagles isn't that difficult:

http://www.wildlightphoto.com/birds/accipitridae/baea00.html
http://www.wildlightphoto.com/birds/accipitridae/goea01.html

other birds too:

http://www.wildlightphoto.com/birds/accipitridae/ssha00.html
http://www.wildlightphoto.com/birds/pelicanidae/awpe00.html
http://www.wildlightphoto.com/birds/laridae/hegu00.html
http://www.wildlightphoto.com/birds/rynchopidae/blsk00.html
http://www.wildlightphoto.com/birds/recurvirostridae/amav00.html

Note that all these flight photos were made with f/6.8 Telyts.  IMHO a good
viewfinder and a responsive lens are best: SL, SL2, R8, R9 and an f/6.8
Telyt.

What a predictive AF system does is observe the dx/dt of the bird, use the
known dt of the shutter lag, and assuming a straight-line flight, calculate
a new dx from the time the shutter relase was pressed.  It can't predict
zigs or zags.

Doug Herr
Birdman of Sacramento
http://www.wildlightphoto.com


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