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Shadowy Daisy
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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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1k views

How does color affect auto-focus?

I've noticed that the subject color seems to affect auto-focus, and am curious if I am just imagining this, or if there is a reason for it. For instance, I shoot a lot of figure skaters, and ...
9
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3answers
2k views

Is the color of the AF assist light important?

What are the differences between white and this darkroom red/orange active autofocus assistance lights?
8
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4answers
2k views

Shooting full manual during an event or function

I have been shooting quite a bit of events lately. I do pre-shoot prep on my camera gear and check out the venue ahead of time to evaluate the setting and how the event will run plus light quality to ...
8
votes
4answers
953 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?
8
votes
6answers
724 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, ...
8
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3answers
1k views

When a camera auto-focuses, is the current focus distance reported from the lens to the camera?

The question says it all -- does the camera "know" how far the subject is from the lens, i.e. what is the current exact focus distance set at the lens?
8
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2answers
722 views

Why the AF confirm lights won't blink when the spot is in-focus while using an all-manual lens with an adapter without any connectors?

I understand that my Canon 450D's (XSi/Kiss X2) passive autofocus system knows a spot in the view is in-focus when its nearby contrast is adequate. Then the camera blinks AF confirm lights to inform ...
8
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5answers
671 views

How to precisely focus in self-portraiture with very wide aperture?

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 2/...
8
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1answer
391 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
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2answers
998 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 ...
8
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1answer
35k views

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

Recently I bought a Canon 60D and I am uncertain about when and how to use/activate the AI Focus and AI Servo functions. I understand the One Shot autofocus function for still subjects. You press ...
8
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2answers
4k 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, ...
8
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3answers
182 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 ...
8
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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
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3answers
9k 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
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1answer
1k views

Why are photos taken with my old lenses all out of focus on my new Nikon D5300 body?

My Nikon D80 died, and I was bought a new D5300, body only. All the photographs are out of focus when I use the lenses I used with my D80. Why would this be? I'm using the Sigma 18-50 f/3.5-5.6 DC, ...
7
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4answers
318 views

Why does holding the focus and recomposing also affect the brightness of my photo?

Let's say I try to take a picture of the following scene: a nice, blue river on the bottom and a solid, grey building in the middle. It is a sunny day and I am in a large distance, so both "objects" ...
7
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4answers
996 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
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1answer
9k 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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2answers
5k 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 ...
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6answers
2k views

If I'm using only one focus point, am I doing it wrong?

Unless I have to shot a person or an object which moves, I set my camera to use only one focus point at the middle. It feels just more natural and so easy: when I need to focus on something which is ...
7
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1answer
1k 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
3k 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 ...
7
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1answer
4k 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
23k 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. ...
7
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3answers
1k 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
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1answer
10k 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
1answer
821 views

What is Nano USM and how does it compare to an STM or USM lens?

The Canon EF-S 18-135mm f/3.5-5.6 IS USM has a designation of Nano USM on the lens. What does this mean? What are the advantages of having it vs STM or USM? We have a terminology thread that usually ...
7
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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

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 ...
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1answer
2k 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
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2answers
810 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 ...
6
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6answers
2k 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 EOS-...
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4answers
2k 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
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2answers
2k 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
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4answers
18k 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
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5answers
716 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? ...
6
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3answers
4k views

Can I determine if an image was captured using Manual or Auto mode?

Is there a way to find out if a picture (once taken) was taken in Manual vs. Auto mode? My daughter is in a photography class and we both have taken images with the same camera. I sometimes put it ...
6
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2answers
430 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 predictably....
6
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2answers
3k 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 focus-and-...
6
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1answer
1k 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
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3answers
575 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
591 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
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3answers
8k 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 ...
6
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2answers
179 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
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3answers
8k views

Why can't I access Single Point Spot AF even when it is enabled on my 5D Mark III?

I have been using Canon 5D Mark III since long but somehow never been able to get across this thing. With the advanced 61 point focus system which the Mark III has, I have always missed the ability to ...
6
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4answers
3k views

What causes auto-focus “freezing”?

On occasion, the auto-focus system in my camera and/or lens just stops working. I'll be holding down the shutter release halfway and tracking a subject and I can feel/hear the auto-focus system ...
6
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3answers
544 views

Why isn't infrared AF assist beam the default when available (instead of irritating strobing)?

I have an entry level Canon camera with a built-in flash. When I try to photograph people at night the camera fires some pre-flashes to help with focus. While I do understand its necessity, some of ...
6
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2answers
435 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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3answers
1k 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 ...