[manpo79]

謝謝

[allen000]

http://regex.info/blog/photo-tech/focus-chart

[wesleyyau]

我諗樓主係問AF Microadjustment 個原理是什麼.. 而唔係點樣check af 係唔係走焦... :p

[MN56]

Canon新機塊CMOS，係用三點floating support。利用三點彈簧既微調去fine tune focus。

[manpo79]

即是個cmos 可以移動?但個移動距離會好微細,真係做到咁準確?

[UFJ]

Should be electronic compensation rather than mechanical movement !!?

Remember, AF Microadjustment can be set for 20 lenses. If mechanical movement, it moves every time you change the lens ??!

[UFJ]

Should be electronic compensation rather than mechanical movement !!?

That is to say, electronic signal will be given to drive the lens in either direction for extra very small distance to focus more close or away from your object.

[no5]

我覺得係software上control~~~
eg. 你set左支len既value, 佢就會次次係auto-focus中左之後~~自己加上你要既數值~

[MN56]

mechanical movement 有乜問題呢？鏡頭AF都係咁做姐！以前Contax有部AF機，係用移動機背來對焦架。

[allen000]

absolutely mechanical ... movement of the focusing element within the lens

AF is essentially a contrast-based iterative process - the body determines the contrast at the focal point, and tells the focusing element to move backwards and forwards bit by bit until it hits the point where the contrast the body considers to be the highest.

Everyone with a little mathematical background knows about the limitation of iteration ... it will get you close to the right answer but never quite exactly there (except by chance). That's where AF microadjustment comes in ... you simply preset an amount of offset for the body/lens combo so that it will be closer to the correct focal point.