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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

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1answer
250 views

How do repair shops fix focus shifts on bodies lacking focus microadjustment feature?

For camera bodies without autofocus microadjustment capability, how do repair shops calibrate a specific body and a lens combination suffering from the focus shifts (back and/or front focusing)?
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 ...
8
votes
3answers
166 views

Is there a rating, spec or measurement that a buyer can use to compare how fast cameras can autofocus?

I know that Phase Detection autofocus is faster than Contrast Measurement autofocus. Is there a spec that can tell me whether one DSLR or compact camera can achieve autofocus on a subject faster ...
7
votes
3answers
3k views

What do the AF-A, AF-C, and AF-S autofocus settings mean?

My camera has these settings for autofocus, and I don't know what they mean. I suspect "A" is "Auto", and "C" is "continuous", but I have no idea what "S" is.
7
votes
4answers
698 views

Which is better - autofocus and recompose vs. manual focus?

In some occasions autofocus doesn't focus what I intend it to. What is the better option - to use autofocus, focus what I want and recompose, or use manual focus in that situation?
7
votes
4answers
630 views

Why does my lens focus better/faster with a speedlight attached to the camera?

I have a Nikon d90 and have often found that the camera reaches focus faster, with less re-adjusting and missing the focus, when I have a speedlight (the Nikon sb-600 in my case) attached. Why is ...
7
votes
1answer
4k views

What are the AF-A, AF-C and AF-S autofocus modes, and how and when should I use each one?

I have seen these autofocus options on all my Nikon DSLR cameras (D50, D80, D90) but I have never really used them. There is the AF button on top. What are AF-A, AF-C, and AF-S ? How do I use ...
7
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5answers
470 views

Precise focus in self-portraiture

I've been trying to take some self-portraits, but I often have to struggle with the auto/manual focus. I don't miss by a lot, but I really want sharp focus in the eyes. I'm using a 50mm/1.8 around ...
7
votes
3answers
908 views

What causes auto focus to misfocus?

If I understand correctly, autofocus works with contrast detection or phase detection, and both of these systems are in the camera rather than the lens. Surely then, the camera just needs to control ...
7
votes
1answer
636 views

What is EOS iTR AF?

I have read references to this feature on some Canon DSLR cameras and am wondering what benefits or uses it has.
7
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1answer
6k views

Can I fine tune the autofocus on my Canon 60D to be more accurate?

I noticed that some of my lenses auto-focus more accurately then others. (Assume perfect light conditions and fast shutter speed) Zooming-in on say the center focus point (if only the center focus ...
7
votes
3answers
2k views

How should I chose a manual focusing screen for my Pentax K10D?

I am considering buying a split focusing screen, replacing the original one. I would like to use some split/microprism screen to ease the focusing of the manual lenses. I own both kit lenses (18-55, ...
7
votes
1answer
2k views

How do you trap focus on DSLRs without native support for it?

I came across the term trap focus on the autofocus page of wikipedia, and it seems to be a very handy feature that triggers the shutter release when a subject moves into the focal plane. This feature ...
7
votes
2answers
751 views

How do I focus a Nikon 50mm f/1.8?

I recently bought this lens, but it seems to me that it hunts a lot in low(ish) light, and sometimes (often) does not achieve focus at all. I never had any problems with the kit lens. Pointing the AF ...
7
votes
1answer
385 views

What are the differences between AF/metering chips for M42 lens Canon DSLR adapter?

I'm looking for an adapter to use an M42 lens on a Canon DSLR. I was wondering if anyone knows the difference between the following types of chips : 2nd generation AF 3rd generation AF EMF AF ...
7
votes
1answer
717 views

What technical reasons prevent Canon's new hybrid AF working with non-STM lenses?

Canon's new Rebel T4i (a.k.a. EOS 650D) has a new "hybrid AF" mode, which allows continuous AF during video, but only when used with one of the new STM lenses. I've seen chatter on the web forums ...
6
votes
6answers
1k views

Is it important that the Canon 1DX isn't specified to autofocus with lenses slower than f/5.6? [closed]

Seeking the lens market AND the related info WRT Canon 1D X, I found some things which seems concerning: 1st, a note from Canon's Chuck Westerfall (see here) saying: “AF is unavailable on the ...
6
votes
4answers
800 views

How important is auto-focus with a 50mm lens?

I have a Nikon D5000. I have wanted the 50mm AF-S as a portrait lenses for a while, but it was sold out forever. I finally broke down and got the older 50mm AF. Good lens, but no auto-focus on my ...
6
votes
3answers
15k 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 ...
6
votes
2answers
1k views

Why can't my camera autofocus in low light with a small aperture?

My question is not about "how to focus in the low light" or "how to focus a camera". The question is why the camera is unable to auto-focus in low light with high f numbers? In these conditions, I ...
6
votes
2answers
216 views

When do you not want to use continuous autofocus (C-AF)?

This Nikon promotion website sums up when to use single autofocus and when to use continuous autofocus. (http://imaging.nikon.com/history/basics/16/03.htm) So, basically if you want to ...
6
votes
2answers
1k views

If the focal plane is curved, should the outer AF points work correctly or front-focus?

Many (all?) lenses have a (slightly) curved focal plane. In general it's close enough to flat that you don't really notice it, but under certain conditions it may become apparent. As I understand it ...
6
votes
1answer
560 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 ...
6
votes
1answer
368 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 ...
6
votes
3answers
392 views

How does the Nikon D40 decide which focus location to use?

How does the D40 decide which focus location to use? It always seems to choose the wrong focus area.
6
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2answers
491 views

What is being set with Micro Focus Adjustment?

An autofocus system is system based on a feedback loop, where the AF sensor error reading if fed back to the lens focus motor. Being a closed loop, then theoretically there should be no focusing ...
6
votes
1answer
4k 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. ...
6
votes
2answers
130 views

Can I intercept and interpret the autofocus signals sent to the lens?

I would like to use a Nikon D80 body with a reflecting telescope as the lens to take pictures of bright/textured objects in the night sky (e.g. the moon). The D80 has autofocus capabilities; the ...
6
votes
2answers
970 views

How does the eye-controlled focussing of the Canon EOS 5 work?

I just read that the Canon EOS 5 had eye-controlled focussing. How does this work? In this short article I found that it had to do with the coupling of infrared eye-tracking and the AF-point choice, ...
6
votes
2answers
234 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 ...
6
votes
1answer
664 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 ...
6
votes
3answers
620 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
5answers
2k views

Why am I getting poor AF results with my Pentax K10D?

I've been using Pentax K10D for a while and I'm a bit frustrated with performance of auto focus on that camera. Very often the images are not sharp enough despite taken in with decent lens (e.g. ...
5
votes
2answers
312 views

Why isn't there an adapter to make manual lenses autofocus?

I was wondering why nobody has come up with an adapter to autofocus lenses like 50 mm f1.8 on lower-end Nikons like the D60. I believe that the lens and the body lack a motor to autofocus. Why can't ...
5
votes
5answers
251 views

With the advantages of an AF-ON button, why don't all DSLRs have one?

I've just updated my body from Nikon D40X to Nikon D300 and realized that the D300 has a AF-ON button on the rear of body. That button's feature do the same as half-pressing shutter button, which ...
5
votes
4answers
615 views

Will I regret buying an older lens that doesn't autofocus or have image stabilization with my Nikon D5000?

I am planning to buy a Nikon Normal AF Nikkor 50mm f/1.8D Autofocus Lens. It doesn't autofocus on the D5000 but for the price, I think it's a good choice of lens for portrait. What do you think? ...
5
votes
3answers
625 views

Is there a way to make the Canon 7D warn when a lens is not in Auto Focus mode?

I pretty much shoot all the time in manual focus mode. I often borrow my girlfriend's most excellent Sigma 8-16mm ultra wide angle lens. She almost always shoots in Auto Focus mode. When I return it ...
5
votes
4answers
374 views

Replacing my XXD with a 7D?

My goto camera is still my 5D Mark II. As I primarily shoot landscape, I love Wide Angle on a Full Frame body. That said, I do occasionally shoot animals and people running. The 5D Mark II's AF ...
5
votes
2answers
335 views

What is the reason to use fewer points than the maximum available for the autofocus?

According to the manual, Nikon D7000 has three options for the number of autofocus points: 9, 21 and 39 points. The manual explains that less points may be used when the subject is moving ...
5
votes
2answers
875 views

Can't auto-focus at full zoom

I have a Canon 1000d, and the standard lens EF-S 18-55mm. Recently I was out taking photos and I've noticed that if I zoom in fully, the lens can't auto focus. I can still take shots using manual ...
5
votes
7answers
10k views

How can I focus in very low light with my Canon 60D?

I'm using a Canon 60D and would like to focus in low light. I know Canons — in fact, all cameras — can struggle here with auto focus, but I'm talking about light so low that I wouldn't be able to see ...
5
votes
3answers
1k views

Are there cheap or DIY focus assist solutions for the Canon 5D?

I want a better autofocus system for low light. Low light auto focus is my biggest bane. I use a 5D so the options are AF on a flash like the 430 or 580. I happen to use the Pocket Wizard TT1 so I ...
5
votes
3answers
407 views

Do I need a better Camera or do I need to learn how to use the one I have?

Read some of the old questions. I figure that due to my wants you may be able to help me. Let me be clear about what I am doing, what I want to do, and see where we can go from there. I help run ...
5
votes
3answers
778 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 ...
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 ...
5
votes
1answer
16k views

What is the difference between Al Focus and Al Servo autofocus modes?

Recently I bought a Canon 60D and I am uncertain about when and how to use/activate the Al Focus and Al Servo functions. I understand the One Shot autofocus function for still subjects. You press ...
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 ...
5
votes
2answers
99 views

Does “the same” lens, with different autofocus systems, have the same optical quality?

I'll give examples with Nikon only, but the question is pretty general. So, is this a fact or not? Examples: Nikkor 50/1.8G AF-S, Nikkor 50/1.8 AF-D and Nikkor 50/1.8 AF 70-300 AF and 70-300 AF-S ...
5
votes
6answers
13k 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 ...
5
votes
2answers
1k views

Shutter half-press to focus possible in Live View mode on EOS 50D?

When not in Live View mode and when the lens is set to AF mode, when I press the shutter button half way on my Canon EOS 50D it causes the camera to auto-focus, as expected. In Live View mode, I have ...