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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.

learn more… | top users | synonyms

4
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3answers
2k views

How do I keep my Nikon D5100 from attempting to autofocus with every shutter press?

I have a Nikon D5100 and the auto focus works fairly well most of the time. But there are times when I have a subject in focus and want to fire off multiple shots fairly quickly. I do not need to ...
0
votes
1answer
288 views

Nikon AF-S Nikkor 70-300mm 1:4.5-5.6 G ED Lens will not autofocus

I have a Nikon AF-S Nikkor 70-300mm 1:4.5-5.6 G ED Lens that I purchased in Feb of 2013. I have been using this lens with my Nikon D3200. Up until this point my lens and camera have been completely ...
0
votes
1answer
2k views

How to fix inoperative autofocus in 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 ...
8
votes
2answers
4k views

How to enable Canon AF with teleconverter?

Canon DSLR bodies prevent poor auto-focus performance by disabling it completely when the lens reports maximum aperture at chosen focal length smaller than f/5.6. This implies that some lenses will ...
1
vote
2answers
117 views

Quiet video autofocus on a consumer level SLR? [closed]

I bought a Canon Rebel T3 a while back before doing my homework on the features. The video quality looks very good to me. However, I have to hold down the shutter button to keep focus. The auto-focus ...
4
votes
0answers
111 views

Halos on images taken with a Panasonic Lumix DMC-FS35 [closed]

Every image I take with my DMC-FS35 shows a halo around the subject. (See below) This is true in all light conditions with or without flash. INSERT IMAGE HERE
1
vote
4answers
641 views

Will the Canon 5D MK II with 100-400 1:4.5-5.6 work properly with Kenko 1.4 converter?

I'm using 5D MKII body and 100-400 f/4.5-5.6 lens. I want to use a 1.4 converter; will the Kenko converter work and autofocus properly?
6
votes
1answer
803 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 ...
15
votes
4answers
2k 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 ...
1
vote
1answer
262 views

Finding the distance of object from camera to the point of autofocus

Is it possible to find the distance to which the camera is auto focussing ? Camera auto focuses itself to view a particular plane in the real world in front of it. Is it possible to estimate the ...
4
votes
2answers
823 views

Why is the AF confirmation chip needed?

I've read that adapter rings for manual lenses in Canon and Nikon might incorporate an Autofocus Confirmation chip... With my old Pentax K10D all manual Pentax-K lenses had AF confirmation, and they ...
3
votes
2answers
2k views

What is a Dual pixel autofocus?

I have seen the term "Dual Pixel CMOS autofocus" used by Canon (specifically in relation to the 70D). What is it? Is this Canon specific technology? Are there equivalents in other manufacturer's ...
1
vote
2answers
876 views

How to achieve auto focusing with a non-TTL flash (YN-560 II) in low light situation?

I recently bought a new YN-560 II hotshoe flash but found that it has neither TTL nor assist beam for focusing in low light situations. The problem now is that I'm starting my career as a night ...
5
votes
3answers
1k views

Enable Auto focus after timer on Nikon D800?

I'll start with an apology if everyone knows this but me. I bought a Nikon D800 about a month ago (adore), but the wireless remote I used for the D7000 is not compatible. No worries, I'll just ...
29
votes
3answers
3k views

How does autofocus work?

How does auto focus work on modern cameras? How accurate is it?
28
votes
4answers
41k 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?
2
votes
2answers
245 views

In which situtations are cross-type autofocus points better?

I understand that the difference between "regular" autofocus points and cross-type ones is that the latter consist of two diagonal "regular" ones. I also understand that this is better. But what are ...
-2
votes
3answers
523 views

Canon 70-200mm F4 L USM IS Focus Issues Photo All Soft?

Focus Issues Bought myself a used Canon 70-200mm F4 L USM IS Lens but as yet I've not achieved a single Sharp image list of various settings tried attempts so far and still no joy very frustrating. I ...
3
votes
1answer
2k views

What happens to a lens when you turn the focus ring during AF mode?

What happens to a lens when you turn the focus ring during AF mode? I have read that this causes damage, or can cause damage. But what is actually happening? I've done this recently with my Canon EF ...
2
votes
3answers
305 views

How to correctly focus on the background person in a shot?

I tried to take some portraits of my sister-in and her fiance earlier in a sunny, green park. I took a few pictures where the fiance is closest to me but turning to look at his wife-to-be who is ...
1
vote
2answers
593 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 ...
1
vote
2answers
337 views

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 ...
-3
votes
2answers
142 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 ...
2
votes
2answers
5k 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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vote
3answers
5k 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 ...
2
votes
1answer
146 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 ...
6
votes
2answers
253 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 ...
9
votes
8answers
3k 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 ...
11
votes
4answers
596 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. ...
3
votes
2answers
2k 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 ...
2
votes
2answers
661 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 ...
3
votes
2answers
3k 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 ...
2
votes
1answer
993 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 ...
5
votes
3answers
4k 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 ...
2
votes
1answer
111 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 ...
3
votes
3answers
756 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" ...
47
votes
4answers
14k 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 ...
3
votes
1answer
1k 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 ...
2
votes
2answers
2k 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 ...
6
votes
3answers
694 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 ...
5
votes
2answers
3k 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 ...
5
votes
6answers
15k 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 ...
6
votes
1answer
644 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 ...
2
votes
2answers
293 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. ...
0
votes
3answers
2k 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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vote
2answers
2k 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 ...
6
votes
1answer
493 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 ...
5
votes
1answer
1k 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 ...
2
votes
5answers
4k 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 ...
13
votes
1answer
12k 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 ...