Autofocus is the ability of a camera/lens system to automatically adjust the focus of the lens via a motor attached to the focus group of the lens. Contrast with manual focus.
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What might be causing my AF system to misfocus?
I have a Canon Rebel T1i with the default Canon lens.
When I shoot with it, I use Auto Focus and get the red dot indicators in the viewfinder as expected.
But even though it looks like the camera is ...
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2answers
98 views
Understanding Auto focus capability with examples
There are lot of explanations/comparisons of auto focus capability of different cameras available.
Canon 5D Mark III has been termed as a superior camera for this feature in the semi-pro range. In ...
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2answers
2k views
Why does my Nikon D3100 no longer auto-focus via the viewfinder?
My Nikon D3100 out of the blue cannot focus correctly.
It seem the that the focus motor always stops at the end of the run (Infinity) and cannot lock on the target, thus cannot release the shutter. I ...
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3answers
166 views
What does infinity focus mean and when should I use it?
All my lens have focus ring where at the end there's an infinity symbol. What does that mean? If I'm taking landscape shot and what everything from near to far to be in focus, do I use infinity? Or am ...
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1answer
71 views
Circular Polarization and Passive autofocus [duplicate]
Couple of weeks ago, I was assigned a homework in one of my Applied Physics master's course. My professor asked to explain why passive autofocus works only with circular polarizers.
I am not a very ...
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2answers
129 views
How does contrast detection autofocus choose its targets?
If I understand correctly the difference between CDAF and PDAF, CDAF basically does not have knowledge of distance while PDAF does. CDAF simply maximizes contrast. So if that is the case how does it ...
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8answers
2k views
Should auto-focus need adjusting?
I own a Canon XTI, and it always seems my shots are slightly out of focus. I usual have my camera set to the center focus point, and usually half press the shutter button to establish the focus on the ...
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4answers
269 views
Why aren't lenses designed with extra large apertures for autofocus beyond what's used for imaging?
Historically, designing large-aperture lenses has been difficult because correcting the optical aberrations that arise from large apertures requires complex designs and very large amounts of glass. ...
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2answers
116 views
Why is on sensor PDAF drastically slower than traditional PDAF?
Why is on sensor PDAF drastically slower than traditional PDAF? I assume the technology is the same, doesn't matter if the module is on the sensor or located behind a mirror. But the performance is ...
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2answers
116 views
Nikon D5100 intermittent focusing problem
I'm having this intermittent problem that the camera does not want to focus in auto-focus. When this happens I try to switch to manual on the lens, (both 300mm, and 55mm) but the toggle button will ...
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3answers
6k views
What apertures are required to enable autofocus, including cross-type or high-precision focusing, on Canon DSLR cameras?
This is a follow-up to Why does Canon and Nikon limit or disable autofocus beyond certain f-numbers? I'm doing this to separate the AF aperture requirements from the linked question above. My goal ...
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2answers
402 views
Do the issues with sharpness I am seeing require AF fine-tuning?
I own a nikon D7000 with 18-105 lens. I am not happy with sharpness I get with autofocus in portraits. I read about front/back focusing, but I am not sure whether my gear has this issue. Is this issue ...
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1answer
645 views
How can I make phase-detection AF more accurate with a Canon 650d and 50mm/1.8?
This is what I get pretty much every time when shooting in Live View mode using the Canon 50 1.8:
This is what I get when I'm lucky when focusing through the viewfinder:
This is what I get when ...
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1answer
168 views
How can I repair a kit lens with a stuck auto/manual focus mode switch?
Recently got a Nikon D5100. After a few days I realized that I can't focus in manual mode. The auto-manual (A-M) switch on the lens seems to be the issue (I have to press the switch hard to manually ...
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3answers
2k views
Why does my Nikon D5000's AF Assist only turn on in some automatic modes?
I am using a Nikon D5000 with a 50mm f/1.4 with autofocus. When I try to use manual mode (or aperture priority, or shutter priority), my AF assist beam does not light, which makes it hard for my ...
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1answer
64 views
Does using multiple batteries (via grip) improve AF speed?
I want to say I read somewhere that, particularly with heavier lenses (such as the 70-200 F/2.8), having two batteries in the portrait grip would provide extra juice to the AF motor and help it ...
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3answers
93 views
Is focus hunting “normal behavior” for the Sony SEL18200SE?
I recently bought an NEX-6, the 24mm F1.8 (SEL24F18Z) lens, and the black 18-200mm F3.5-6.3 (SEL18200LE) lens. I love the 24mm lens, but I'm having a what I believe one would call a "focus hunting" ...
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0answers
42 views
Nikkor AF-S 28-70mm 1:2.8 D autofocus problem
I had this lens for quite a few years now, it used to work as expected. I didn't use my stuff for a few months, maybe 6-8 months. I just bought a D600 and tried to use them. The AF does not work as it ...
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1answer
80 views
Nikon d5100 won't autofocus at all
A good friend of mine has a d5100, which was working perfectly fine yesterday. Today, however, it refuses to autofocus at all - it makes no effort to move the focusing ring etc.
I have tried ...
43
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4answers
9k views
What is the best way to micro-adjust a lens?
I have a Canon 7D with a 50mm f/1.4 lens, and I think the auto-focus of the lens is off. How can I test and adjust this reliably?
Will this approach work with all of my lenses? If I had a different ...
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1answer
88 views
What settings affect how the focus points are displayed for my 7D?
My Canon 7d is about 2 months old. I used it for a shoot in DC, and it just isn't behaving as expected. When I try to focus, I get little black boxes in the focus frame. They used to be black, with ...
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1answer
220 views
Why isn't the focus indicator light showing when focused on my Canon 5D Mark III?
I've been working with two different Canon EOS 5D mark III cameras, and had the same problem with both.
When auto-focusing I have two kind of indicators when the image is focused on a certain point.
...
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3answers
237 views
Missing focus with Canon 50mm 1.8 lens - is it the lens or me?
I purchased a Canon EOS 650D and EF 50mm f/1.8 II lens.
Unfortunately, the auto-focus seems to miss focus at f/1.8. I've tried setting it to single-point auto-focus: it is better, but still not good ...
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2answers
167 views
Do I use the camera or lens switch to change between auto and manual focus?
I own Nikon D7000 with 18-105mm lens. I am bit confused how the auto focus and manual focus switching works, particularly with my gear. The confusing part is both the camera and lens have an A-M ...
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3answers
392 views
Have I broken my Canon 28-135mm lens after DIY repair?
Last week I removed the front element from my Canon 28 - 135mm lens to remove a grain of sand from the lens. It was easy to remove the 4 screws, take of the top layer of glass and remove the grain.
I ...
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2answers
192 views
What is the effect of the number of cross-type focus points on sharp focus?
Canon claims that EOS 6D has special capability to focus in low light, but it has only one cross-type sensor and overall only 11 focus points. Does only one cross-type focus point in the Canon EOS 6D ...
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4answers
22k views
What is back-focusing?
What is back-focusing? Is it something I need to be worried about, or can I just live with it? How can I tell if my camera/lens is sufferring from it?
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1answer
799 views
Autofocus Not Working on Canon 70-200 F4 L USM
This lens has been sitting on the shelf for years and I recently hauled out my DSLR to play with it. Turns out the autofocus no longer works. I'm wondering if there's any kind of remedy for this short ...
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0answers
65 views
Nikon D3100 won't autofocus [duplicate]
I have a Nikon D3100, and I found out recently that when I half-press the shutter to focus, it wont autofocus anymore. I've tried it with another lens - still the same problem. The autofocus is ...
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4answers
392 views
What can I do if autofocus does not work but manual focus does?
Recently, the autofocus on my Nikon D3100 stopped working. The ring of the lens wouldn't even turn when I tried to focus. However, when switched to manual focus, the camera works fine.
When I used a ...
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6answers
7k views
Why does my Nikon D3100 no longer auto-focus correctly?
I bought my camera on January 2011. Since a few months ago, I'm facing a problem with the autofocus.
It happens with my two lenses 18/55mm and 55/200mm. I noticed that the focus light doesn't turn on ...
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1answer
230 views
What do orange AF points mean on a Canon DSLR?
I recently bought a Canon 7D and Ive noticed that occasionally the AF points are orange. What conditions cause this? It seems like it is a warning of some sort.
Usually when the camera focuses on a ...
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3answers
410 views
Where is Canon 1100D autofocussing in low light low contrast conditions?
It's obviously my fault for living in the UK and expecting to want to enjoy my bird photography in grey January afternoons, but, I would appreciate some opinions on the following.
I took 150 shots ...
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2answers
123 views
Should Canon 5D mk II autofocus be accurate enough for a f/1.2 lens?
What autofocus accuracy can be expected from an EOS 5DII or EOS 5DIII camera?
I have an EOS 5DII with f/1.2 and f/1.4 lenses. I have a lot of problems getting consistent autofocus with these lenses. ...
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3answers
1k views
How can I get better focus results with my Nikon D90 at a fashion show?
I shot at a fashion show last week, and had focus problems. I used my Nikon D90 with a Sigma 70-200mm f/2.8, with no flash.
I tried many autofocus settings but none of them worked. I also tried ...
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1answer
2k views
Nikon D5100 Focusing Issue
The issue I have had is where the camera tries to focus and cannot focus. It just zooms in and out constantly and no matter what I do it will not focus and fire. The only way I have found around this ...
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1answer
121 views
Why isn't the gain on phase-detect autofocus sensors increased in low light?
Modern phase-detect sensors can focus in pretty low light. However, the limit for low light focusing tends to be reached much before the camera can no longer capture images using a high imaging sensor ...
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2answers
392 views
Why are images with my Nikon D7000 and 70-200mm lens soft?
I'm having trouble getting sharp pictures with my D7000. I've tried it with a 70-200 and 18-70 and produce the same results. I've tried AF Fine Tune with one of those focus charts, but the value of 0 ...
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4answers
1k views
Why can't my SLR autofocus on certain parts of a scene?
I had my Nikon D7000 on single-point auto focus and it just would not focus on the spots I wanted. I have marked the spots that could not be focused on with red circles, and the parts that could be ...
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5answers
327 views
Why is the main sensor not used instead of the separate AF sensor to focus a DSLR?
From this answer I understand that the reflex mirror of a DSLR is actually not reflecting all the light, but it passes a certain amount on to the AF sensor.
So if the reflex mirror can pass light, ...
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1answer
183 views
Where is the AF sensor located in a DSLR?
As I understand every DSLR has a separate, smaller sensor that handles phase detection focusing. Where is it located?
If this location is different for every DSLR, and therefore this broad question ...
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1answer
174 views
Why does the IR-Assist beam of Canon Speedlites not get used in AI Servo AF mode?
The IR AF-assist beam on the Canon Speedlites (I have a 430 EX II) doesn't seem to come on when the DSLR (I have the EOS 7D) is in 'AI Servo' AF-mode. It works fine if I'm in one-shot mode (comes on ...
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5answers
373 views
Why my “action” shots are blurry even shooting on AF-C, is this a lens or camera limitation?
I'm currently using a Nikon 28-200mm AF-D with my D7000. While trying to take action shots (e.g. my dog running or sports) none of the shots seem to be in focus even on AF-C mode. Would this be a ...
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1answer
2k views
How does focus work on mobile phone cameras?
How does focusing work on mobile phone cameras?
Aren't their optics simple enough to not have any moving parts whatsoever?
If so, how come most smartphones have an auto-focus, and with various ...
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2answers
318 views
Why does Nikon D3100 locks Shutter in Autofocus mode?
So I just got this Nikon D3100 Camera. And I am trying to take a picture using autofocus with the kit lens(18-55mm).
The system is in Auto mode, AF-A, single frame and the lens A-M switch is on ...
9
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3answers
813 views
Why do mirrorless cameras have quicker autofocus than SLRs using live view?
With early 2013 cameras, it's generally accepted that using contrast detection autofocus on SLRs (ie live view on most SLRs) is something which is really suitable only for static, or close to static, ...
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1answer
185 views
Does Canon T4i's phase-detection auto-focus system really out perform the common contrast-detection systems (e.g D5200)? [closed]
I believed that T4i's phase detection is really a winner for taking videos with auto-focus, until I read this post.
Has anyone else experienced any practical difference in the quality of videos, ...
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2answers
331 views
What kind of AF-motor does a Nikon D7000 body have?
I am a novice in the SLR photography world and am going to buy my first camera. I intend to take occasional videos. I guess if the AF-motor is screw and gear type, the clicking noise will ruin the ...
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3answers
9k views
Is the lack of AF Motor on the Nikon D5100 an important factor?
I had made up mind on purchasing a Nikon D5100 during the holidays but only yesterday I realized that it doesn't have a AF motor with it.
This is forcing me to change to Canon 550D which is in the ...
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1answer
260 views
Which offers better results: FoCal or LensAlign Pro?
I am in need of microadjusting my autofocus for a couple of my lenses with my Canon 7D. Namely, I need to adjust the 100-400 L lens, which seems to consistently AF a bit softer than I've seen from ...
