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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
151 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
259 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 ...
11
votes
4answers
607 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
1answer
117 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
821 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" ...
3
votes
3answers
358 views

What can I do when autofocus suddenly starts blocking at around 2m on a Nikkor AF-S 28-70mm 1:2.8 D?

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 ...
1
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1answer
6k views

How to troubleshoot a Nikon D5100 that will not 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 ...
3
votes
1answer
2k 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 ...
6
votes
1answer
7k 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. ...
4
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4answers
4k 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 ...
2
votes
2answers
3k 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 ...
2
votes
2answers
698 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 ...
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 ...
6
votes
1answer
671 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
304 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. ...
4
votes
1answer
261 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 ...
1
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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 ...
8
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6answers
511 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, ...
6
votes
1answer
504 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
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1answer
2k 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 ...
3
votes
2answers
4k 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
2answers
4k 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 ...
2
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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 ...
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2answers
2k 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 ...
1
vote
2answers
614 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 ...
0
votes
1answer
81 views

Will a shutter half-press perform an autofocus while shooting video on an EOS 650D?

Have Canon kept this feature or has it gone like the movie cropping mode?
2
votes
1answer
213 views

Why is my ISO so high in auto mode?

New user of a Canon 7D - less than 50 shots taken. Last night, I needed to take a quick picture of something that was on my cell phone with my Canon 7D I propped the phone up against a white pillow ...
11
votes
3answers
4k 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, ...
3
votes
2answers
2k views

Is it safe to manually-focus the Nikon 18-105 while in autofocus mode?

There are only A and M settings, no A/M. but I just noticed that Nikon website has mentioned three focus modes for this lens: Auto, Manual and Manual/Auto I'm confused if this is only a typo or is it ...
1
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1answer
170 views

Can I use a Cosina AF 28-300mm f/4-6.3 with a Nikon D5100 if I focus manually?

The Cosina AF 28-300mm is an autofocus zoom for Nikon F-mount (body must have AF motor). Can I still use it with the D5100, provide that I will have to manual focus?
5
votes
3answers
418 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 ...
4
votes
2answers
463 views

Can I control if the in-body AF motor is used instead of the lens AF motor on my Nikon?

I have Nikon D7000 with 18-105mm. I know that the camera body has the AF motor and the lens itself has the AF motor too. I was wondering can I control which AF motor should be used while autofocusing. ...
3
votes
2answers
2k views

Can a drop of a camera+lens cause AF calibration issues on either — or both — the lens and the body? What are the mechanics involved here?

My question is, if you drop a camera, and you think you might have an AF issue, what are the mechanics involved that might cause a mis-calibration? I can imagine that the lens has movable parts -- ...
4
votes
2answers
1k views

What is the “AF Stop” button on some Canon lenses?

When looking at custom functions in Canon camera manuals, I've come across mention of setting functionality to have happen when the "AF Stop" button is pressed - a button that, apparently, exists on ...
8
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2answers
2k 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, ...
3
votes
1answer
240 views

Why 5-50x focal length for autofocus micro-adjustment?

When we do an AutoFocus Micro Adjustment session, the general opinion is to set the focusing target at 25 x focal length (or somewhere in the range of 5-50 x focal length). Why is so? What happens if ...
3
votes
3answers
1k 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
5k views

Automatic autofocus on 600D/Rebel T3i during video mode [closed]

I was testing the video mode with my 600D, and I noticed autofocus was not working. I then enabled it via the menu and now you can focus when pressing the main button. I was wondering whether this is ...
3
votes
1answer
152 views

Is it normal for live view to freeze when focusing with a point & shoot camera?

I went to a Best Buy recently and tried a few point-and-shoot cameras, among which the Canon G15, Canon SX260, and Canon SX50. With all of them, I noticed that the live view freezes for a short time ...
13
votes
2answers
13k 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 ...
1
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0answers
279 views

Why can I not disable full-range auto-focus in newer point-and-shoot cameras? [closed]

I owned a number of Canon PowerShot cameras (SD300 and SD1000), and I was always pleased with being able to quickly take one out of the pocket, and take a picture within about 2 seconds of noticing ...
12
votes
5answers
1k views

Why don't most cameras use infrared for focusing?

All auto focus assist lights are either red or white. Why do DSLRs not use infrared instead? It seems it would be beneficial to a photographer to not blind their subject before taking a picture. ...
2
votes
1answer
750 views

Why does my D70s no longer focus my Nikkor 70-300, but still focuses the 18-70?

At first I thought my lens was dead but after switching to my other D70s it worked fine. So, here's the issue: One of my D70s bodies can no longer auto-focus my Nikkor 70-300 lens. Switch to a 18-70 ...
10
votes
1answer
344 views

When focusing in Live View, where is the point of focus?

I use Canon SLRs. When using live view focusing, there is a rectangle which turns green when the focus is achieved. My question is: Is there a single focus point at the center of the rectangle? Or ...
6
votes
2answers
140 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 ...
8
votes
1answer
273 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)?
4
votes
2answers
4k views

EOS Rebel T3i 18-55mm lens won't take a picture - happened with two lenses

I'm a reporter for a small town paper - Early in 2012 we had a body of a T3i go bad and it was replaced new body and we used the old 18-55mm lens. It worked fine for 7-8 months. I do a lot of sports ...
4
votes
4answers
5k 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 ...
2
votes
1answer
552 views

How do I make the focus point indicators stay long enough to select on the Canon 60D?

I have just switched from the Canon 500D to a 60D. Most of my work is property based, and this is therefore 90% internal flash shots where I often wish to pick out a particular spot for best focus. ...