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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

9
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2answers
1k views

Can lens focus speed affect continuous shooting speed?

I was using a 50mm f/1.8 II lens on my Canon 40D yesterday, and I was trying to capture some action shots using continuous high-speed drive mode and AI Servo autofocus mode. I was using a shutter ...
17
votes
5answers
2k views

When would one need manual focus override?

In lens reviews, ability to override auto-focus manually is often referred to as a good (and important) feature. I have rarely, if ever used that feature, so I feel I might be missing out on an ...
7
votes
1answer
23k 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
votes
5answers
3k views

How to get focused pictures for action shots?

My daughter just started playing Tee-Ball and I was out there with my Digital Rebel XT and a Sigma 300mm. I know enough to be dangerous and I was shooting in "Auto mode" with the action preset (the ...
8
votes
4answers
792 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?
18
votes
4answers
10k views

How do camera body motors compare to in-lens motors for focusing?

What is the difference between using a motor on the camera body and the motor built into lenses? Aside from how both compare in terms of speed, what differences would I notice if I use a body with a ...
19
votes
2answers
53k views

What's the difference between cross-type autofocus points and regular ones?

What's the difference between different autofocus point types (cross vs point and such)? Cross points seem to be a "feature" — why?
5
votes
3answers
2k 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 ...
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 ...
13
votes
7answers
1k views

How can I improve focus using both manual and auto on a candle flame?

I got my new tripod and 50mm F/1.4 sigma on my Nikon D7000 and was testing it out doing some shots of a flame on a candle. The below image is the sharpest i was able to produce. In review of my 50+ ...
13
votes
4answers
800 views

Why doesn't auto-focus work with an all-white subject (like a wall)?

I am trying to compose a shot using my Nikon D60 and 18-55mm lens towards a white wall in a auto-focus mode. It looks like I am not able to take the photo. I feel the camera is not able to find any ...
5
votes
2answers
1k 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 ...
27
votes
8answers
3k views

What is the advantage to back-button autofocus?

I've heard some advanced photographers talk about using back-button autofocus. As I understand it, this involves changing one of the camera's custom setting to engage the AF when a button on the rear ...
32
votes
5answers
3k views

Focus problem vs. motion blur vs. camera shake - how to tell the difference?

I'm not sure if the title of the question captures what I mean, but it's hard to be succint in the space allowed. Suppose you have a picture that is not as sharp as you think it should/could be. ...
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 ...
13
votes
3answers
1k views

How does the lens influence the autofocus?

I think I've more or less understood how AF works now. However, I'm not sure how the lens influences the whole process. In my recent research for my next lens I found reviews stating the one lens' AF ...
8
votes
2answers
650 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 ...
10
votes
2answers
830 views

What is manual-priority autofocus?

I have been looking at the Nikon AF-S 35mm f1.8 lens and it has two focus settings: Manual Focus Manual-Priority Autofocus What is "manual-priority autofocus"?
12
votes
1answer
5k views

What is a focus limiter?

What is a focus limiter and how does it work? What is the advantage of it? For instance Tamron 90/2.8 Macro has a focus limiter. According to the documentation: In the limit position, the Tamron ...
5
votes
1answer
370 views

AF switch on lens vs. AF switch on camera

Is there any difference between using only the AF/MF switch on my camera (Nikon D90) or using the AF/MF switch on my lens (18-105mm)? Could having autofocus on my camera switched to manual focus ...
8
votes
5answers
534 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 ...
30
votes
3answers
3k views

How does autofocus work?

How does auto focus work on modern cameras? How accurate is it?
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, ...
3
votes
2answers
4k views

Are there solutions to limitations on using back-button AF on Nikon D3100?

I have started to use my D3100 with my AE/AF-L button set to AF. So in other words I use this button instead of the half press shutter button to AF. I'm new to this technique and came across it here ...
0
votes
0answers
345 views

Need help focusing at night with DSLR [duplicate]

Possible Duplicate: How to focus in complete darkness I have a Canon 20D, when I shoot outdoors at night I have a very hard time getting images in focus. I primarily shoot landscapes, so ...
10
votes
3answers
1k views

What type of lens will auto-focus on Nikon bodies without a focus motor?

I know my D40 doesn't have a motor in it to auto-focus lenses. What type of lens has the motor in it? How can I know which lenses will and will not work?
2
votes
2answers
3k views

How to eliminate auto focus noise in video mode when using NIKON D7000?

You can hear the noise when taking a video w/ NIKON D7000 w/ normal lens. Is there any way to get rid of the noise? Will shotgun mic help? Thanks in advance!
5
votes
1answer
213 views

How to Turn Off Custom Functions in Canon Film SLRs

So I adjusted the Custom Function settings in the dial, and then I noticed that my Autofocus is now controlled by the CF button. I am using a Canon EOS 50, a 1995 film camera (not 50D). How do I turn ...
11
votes
6answers
7k views

How can I get everything in focus?

I have a Canon 550D with 70-200 f4 and 50mm prime lenses. Although the camera has built-in 9 focal points, I sometimes face a strange problem. Here's a sample photo: In reference to the above pic, ...
16
votes
5answers
2k views

How to improve focus accuracy?

I've noticed that quite a few of my photos aren't terribly well-focused. This particularly happens at long focal lengths. I'm using a Canon 500D and (mostly) a Tamron 18-270mm f/3.5-6.3 lens. I find ...
2
votes
1answer
994 views

Why did my 50mm f/1.8 Canon lens deactivate autofocus on Canon EOS 1000D?

I recently lent my 50mm f/1.8 lens to a friend who owns a Canon EOS 1000D. Afetrwards he told me that the camera had deactivated autofocus when he switched back to his kit lens (18-55). Is this ...
10
votes
2answers
1k views

How can I determine if my Sigma 10-20mm lens copy is appropriately sharp and focusing right?

I just purchased a Sigma 10-20mm lens (Canon mount) and based on the reviews I was aware that many people receive copies of the lens that are soft or don't focus properly. I purchased from B&H, so ...
5
votes
4answers
381 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 ...
11
votes
3answers
17k views

Will the Nikon D3100 autofocus with the 50mm f/1.8D lens?

I have the Nikon D3100 and was wondering if the autofocus on the Nikon 50mm f/1.8D lens would work with it. I've read that the AF is not compatible with the D5000, and that the AF is rather slow in ...
5
votes
1answer
1k views

Sigma 70-200mm vs. Nikon 80-200mm auto-focus speed

I'm considering the newest Sigma 70-200mm F2.8 EX DG APO MACRO HSM II and comparing it against the older (but still for sale) Nikon AF 80-200mm F2.8 D ED. These are roughly in the same price class, ...
10
votes
4answers
504 views

Focusing on moving target with large aperature?

I have read about difficulties getting focusing right when using a large aperature (because of depth-of-field issues). If I am using a fast prime wide open (say F1.4 or F1.8) to shoot a target in ...
16
votes
2answers
4k views

When to use a particular auto-focus mode

I have a Nikon D90, and after taking a photography course that recommended single point auto-focus I predominately use that. I was testing some of the modes today (single point, dynamic area, ...
7
votes
2answers
769 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 ...
5
votes
4answers
641 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? ...
19
votes
2answers
1k views

Why am I allowed to turn my focusing ring beyond infinity?

Is there a good reason why I can turn the focusing ring on my lenses beyond infinity mark on focusing scale? Following recent questions here and here, it sounds like a real usability issue. ...
27
votes
3answers
1k views

What is the difference between a linear and a circular polarizer?

When I bought my polarizer, a friend told me that I should get a circular one, because the linear ones can mess with the autofocus. Is this true? What should each be used for?
4
votes
4answers
1k views

Why does my Nikon D90 autofocus not work in rapid succession?

When photographing candid shots of my children at play with a Nikon D90, I have trouble with the autofocus system. I focus and shoot one shot, great. But a second later another shot opportunity ...
6
votes
3answers
435 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.
31
votes
4answers
47k 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?
4
votes
2answers
834 views

Force AF assist light on body / flash to come on with Nikon DSLRs?

I have a Nikon D-40 and D-90 with a wide assortment of prime lenses. I like fast primes for low light photography. Some of my lenses are sufficiently old that they do not auto focus at all. Others ...
26
votes
6answers
5k views

Can I damage the focus system by turning the focus ring when the lens isn't mounted?

I have a couple lenses that don't have an internal focusing system, and whenever I want to put them back in my bag, I turn the focus ring to make the lens shorter. I noticed that when the lens is set ...
48
votes
4answers
16k 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 ...