Autofocus as Fast As Possible
Techquickie
·Techquickie
·2015-05-07
·
1,010 words · ~5 min read
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now it used to be that back in the time of the dinosaurs when a person set out
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to take a photograph specifically a not blurry one they would actually have to
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send their assistant out with one end of a measuring rope and then adjust their
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accordion lens to the proper focal distance I mean okay that's a bit of an
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exaggeration but I think you guys get it what I'm driving at here autofocus
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Optical systems like all things photography related are complex and lead
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to the necessity of many highly priced peripherals and accessories or to put it
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a gentler way there are many types of autofocus systems which can be employed
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depending on the necessity or manufacturer specifications thankfully
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these multiple types can be broken down into two very simple camps active and
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passive passive systems come in several different forms but all operate by
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analyzing an image once it has been projected onto one or more sensors then
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adjusting the focus based on the qualities which help it to determine
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subject distance or Clarity since they only respond after an image has already
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been captured and then make adjustments without using environmental data all
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processes they enact are considered passive they are mostly found in two
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basic varieties which are referred to as phase or contrast detection phase
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detection can be found commonly in DSLR style cameras and works by using an item
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called a beam splitter to direct the light from an incoming Source onto two
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separate micro sensors which are placed on opposing sides of the lens
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effectively doubling the image doubling the image doubling the image in older
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cameras the user would manually have to adjust the focus until both images came
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in line but today software is utilized that matches up light intensity patterns
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based on Peaks and valleys allowing it to make a determination about whether
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the subject is back or out in front of
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proper Focus now while phase detection works well on high quality cameras with
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interchangeable lenses the added cost and bulk that accompanies it does not
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always make it a feasible option which by contrast brings us to well contrast
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detection that is at least this form of focusing works by analyzing the pixel
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intensity of an image on the sensor automatically adjusting slightly past
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the point of highest contrast and then back again this is what causes that
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quick blur effect that you might have seen on your viewfinder before snapping
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a shot but lonus I thought you said that there were two different camps of
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autofocus what about that that active thing you mentioned before well yes I
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did say that but in reality it was actually a bit of a tease since
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applications of active autofocusing tend to be on the less than practical side so
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far these devices work in theory by
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physically measuring the distance between it and the subject and operate
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outside the normal functions of the optic system so two implementations of
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this focusing style have been seen so far sonar which uses audible clicks to
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determine the distance to the subject yes just like dolphins do or infrared
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lasers like the one found on the LG G3 smartphone these use a constantly
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measured distance to triangulate the space between the subject in the camera
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and adjust the focus quickly on demand these systems have uh you know some
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failings though such as you know functionality ones like the inability to
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work when shooting something underwater or through a window and more mundane
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ones as well like the annoyance of having your camera click every time you
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take a picture while active Focus can still be considered in the EXP
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experimental stage it seems for the most part the verdict is still out so whether
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you're shooting you know 4K footage of your self performing reviews of latest
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computer components or taking pictures of someone pushing a hoop down a dirt
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road with a stick autofocus has what it takes to keep you in the clear speaking
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of annoying clicks if you're just finding your current job is not clicking
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