How does Auto
focus or focus works in DSLR camera
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| reikanfocal.com |
Focusing
means concentrating on single object in an image and blurring remaining area. The
autofocus (AF) systems in our DSLRs camera on a daily basis, they are one of
the most important aspects of our cameras.
Basically
there are 2 types of focusing systems,
1
-Phase Detection AF
2
-Contrast Detection AF & Dual Pixel AF
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1 -Phase Detection AF
The
most common type of AF in DSLRs today is Phase Detection AF. Phase detection is
achieved by dividing the incoming light into pairs of images and comparing them
by its mechanics & electrically.
If
an image in out of focus then the two images will not line up, & based on
how far off they are, the camera knows which way to focus the lens to achieve
that perfect sharp focus with its artificial intelligence. But hopefully you
get the idea. Check out this how it works through below given diagram.
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2 -Contrast Detection AF
Contrast
Detection AF is another common AF system found in DSLRs like Canon and Nikon
DSLRs. When they are in live view or video mode Contrast Detection is its
primary form of AF.
Auto Focus systems measures the contrast difference between
pixels on the sensor, which naturally increases with perfect focus.The problem
with this kind of AF is that it does not involve any actual measurements and in
bad lighting conditions it can be thrown off, this all leads to contrast detection AF
systems being much slower than phase detection AF systems.
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3 -Dual Pixel CMOS AF
In
a Dual Pixel CMOS AF sensor, two photo-diodes are distributed to each micro-lens.
With Dual Pixel CMOS AF, signals from these two images are used to carry out
phase-difference detection AF. In addition, by combining two photo-diodes, the
image signal can be output as one pixel. This is mostly used in Canon EOS 70D
digital SLR, Nikon AF-S Nikkor 24-70mm f/2.8G ED etc.
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