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Auto Focus Question

Gary,

http://www.navitar.com/download/how_af_works.pdf

Joe

P.S. One your next Mac, make sure you ask Apple to preinstall some kind of engine that searches the World Wide InterWebby. Very handy, these engines that search.

seoglobe-sm.jpg
 
Magic moon beams fire from the camera and bounce back off the object, by doing some hard sums the camera can calculate that time taken = this distance and focus..........

S
 
Joe I like the sense of community and you are beginning to sound like a twonky photonet forum user ;)

The rather excellent news is my iMac has been dispatched today. Yippee.
 
Gary,

I don't mind answering questions or offering advice on lenses and cameras, but you have this annoying habit of not even reading the reply when someone goes to the trouble of answering your question. That's really more the hallmark of twonky photonet forum user.

Joe
 
the auto focus system has to be calibrated , it would be quite easy to make an auto focus system that doesnt , by not doing the calibration / set up properly at the factory.
 
As well as image analysis for contrast (as mentioned in the pdf linked by Joe) many (most?) cameras also use an infrared beam and sensor to measure the distance to the subject. Good AF systems use a combination of the two. In your old E-10 Gary, it used image analysis preferentially but in very low light conditions where there's not a good enough image to work with it used IR sensing hence allowing autofocus to work even in pitch black conditions.

Michael.
 
I am noticing that the ability of the AF seems very lens specific. The older AF lens I have here suffers in lower light compared to the stock lens. My new super zooms focuses very quickly.
 
garyi said:
The rather excellent news is my iMac has been dispatched today. Yippee.
iGary-

I missed the story behind this. Unless it wasn't told here. Did your other Apple(s) break and need to be replaced?
 
garyi said:
How does a camera know its in focus?
Left field answer: It doesn't, the photographer does when he used pre-focus, zone focus, hyperfocal technique etc., used the lens markings (lenses from the olden days...) etc.

I suspect Vuk will be along soon and add that a camera is never in focus, it really is up to the photographer to decide what he wanted sharp and use the attributes of the composition and the lens characteristics as he requires.

Alternatively, it's something to do with CCDs, cross-hair sensors and maths calculations as previously suggested, used to be a big thing in camera brochures, don't know if it still is.
 
The issue with rosetta is interesting. More interesting is who exactly thisd shit app is aimed at. How many people are likely to sit across a sitting room and squint at a 20 inch iMac haha.

Its been resovled thankfully, a software issue.
 
"How many people are likely to sit across a sitting room and squint at a 20 inch iMac haha."

The so called "10 ft interface" and the personal computer as media centre is actually meant to be the latest great strategic growth area that powers Apple from 3% market share to world domination.

I don't buy it either.
 
The fundemental **** up as far as I can see is that you cannot to date run front row on another screen, it has potential if you could do that.
 
I can't see anyone taking Front Row or Microsoft Media Centre seriously at the moment. They're just gimmicks IMO.

Michael.
 


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