Auto focus - is it accurate?

[sirhc55]

For those of you with a technical bent this article may be of interest:

http://www.anstendig.org/AutofocusFlaw.html

[Alpha_7]

Thanks Chris, fair bit to read but it's definitely interesting.

[Steffen]

Goodness gracious me!

This article alternates between stating the bleeding obvious and utter bollocks. To save you five minutes of reading, here's the central postulate:

Therein lies the ultimate, crucial flaw in all auto-focusing systems, a flaw that can never be eliminated: in all auto-focusing systems, the focusing sensors are located in the center of the viewing area.

To be fair, the paper is from 1985, a time when passive AF was still hotly debated and split the world of photography into deeply entrenched, opposing camps. If you keep that in mind some of the musings seem actually quite humourous from today's point of view.

Thanks for sharing Chris!

Cheers
Steffen.

[Greg B]

Thanks Chris, very interesting.

I guess the thing is that something will be at the exact focus distance, so the real question could be - will auto focus
select the same focus point as the photographer would in manual focus mode?

I don't consider it to be an auto focus flaw, rather an attribute of auto focus. As long as we are aware of what the focus
system is doing, and select the appropriate focussing mode, or select manual focus in situations where auto focus can't
give the result we want, then auto focus is fine and dandy.

[Alpha_7]

To be fair, the paper is from 1985, a time when passive AF was still hotly debated and split the world of photography into deeply entrenched, opposing camps. If you keep that in mind some of the musings seem actually quite humourous from today's point of view.

That's why I had the odd feeling I was reading a old science text book, I can't recall the name and google was no help. Big Highschool textbook with a green cover, I think I had my mum's old one.