Alley in Pisa, Italy

by Lars Kotthoff

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Focus is the mechanism of converging light from a point light source onto an imaging plane by a lens.

learn more… | top users | synonyms

92
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7answers
7k views

What is bokeh, exactly?

I understand that "bokeh" refers to out-of-focus areas of an image — but there is obviously more to it than that. What does the term mean exactly? How well is bokeh really understood? Is it purely ...
56
votes
15answers
8k views

How does one focus for landscape photos in very dark conditions?

Tonight I tried my best to take some night landscapes in the darkest of dark conditions. Hoping for an epic composition of the Milky Way and a landmark. Of course, none of my glass could auto focus ...
32
votes
7answers
1k views

What is “Hyperfocal Distance”?

I'd like a clear & easy-to-understand (especially for non-physics-types) explanation of what Hyperfocal Distance is, how it affects photographs, and what determines its value.
32
votes
7answers
6k views

How can I get sharp manual focus despite poor eyesight?

I suffer from astigmatism. It's only mild, though I feel it's affecting what I'm seeing when looking through the viewfinder. Frequently, after shooting a photo with my Canon EOS 7D, I'll load it into ...
28
votes
4answers
39k 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?
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 ...
25
votes
13answers
7k views

How does one get manual focus right with a fast-aperture lens?

I have got an old lens (f1.4) that I have to use only with manual focus on a DSLR. Well, it is difficult for me to get the subject on focus. Although on focus according to the viewfinder, the actual ...
25
votes
6answers
4k 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 ...
24
votes
3answers
2k views

Does changing the focal length change focus?

When using manual focus or back focus on D60, I sometimes zoom in the lens, set the focus, and then zoom out. Does changing the focal length (zooming out), also change the focus? In case the answer ...
23
votes
18answers
2k views

What are some techniques for hand-held image stabilization?

My zoom lens (75-300mm) is fairly slow: 5.6 at its farthest point. (I think it's 3.5-5.6, and it's not image stabilizing. I'm on a budget, sadly!) Unfortunately, my primary use for it is hand-held ...
23
votes
9answers
3k views

Why would I want to select an autofocus point?

I'm trying to understand why I would ever want to select an auto focus point other then the center point. I have a Canon XTI Rebel DSLR which has 9 auto-focus points, but I'm also looking into getting ...
23
votes
5answers
1k views

What are the best practices for DOF stacking?

What are the best practices for DOF stacking? How do you get the frames with focus just right amount apart? How do you stack them in post processing?
23
votes
4answers
2k views

What tips and advice do you have for photographing the Aurora Borealis?

A friend has been kind enough to lend me a DSLR for a few months. It's my first foray into DSLR photography, or indeed any kind of photography beyond simply aiming my Canon IXUS at something and ...
21
votes
3answers
6k views

How can a 18-55mm lens focus on objects beyond 55mm?

I guess this is a total noob question, but doesn't 18-55mm mean that it can focus only up to 55mm?
21
votes
7answers
7k views

How to nail focus for DSLR astrophotography?

I've been doing a bit of astrophotography and the problem that I almost always have is nailing focus. I'll manually focus on a bright star or the moon (which hopefully isn't an option!) by magnifying ...
20
votes
8answers
3k views

How do I focus in low light for long exposures?

I've been trying to take some long exposure shots at night with my Canon 450D. The problem I'm having is that I can't seem to get a shot in focus. The low light conditions prevent AF from working at ...
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. ...
17
votes
2answers
1k views

What makes the focus ring on a lens go smoothly?

I’m curious about the smooth movement of the zoom or focus rings on a lens. How is the smooth movement done? Is there some kind of liquid with high viscosity? That doesn’t sound very probable. On the ...
17
votes
3answers
1k views

How can I get better focus when a subject is moving towards or away from the camera?

When shooting events or action photos, engaging people, I often find that frontal (or rear) perspective may be very expressive, but my problem is focusing when the subject moves towards the camera (or ...
16
votes
1answer
587 views

What is a focusing rail?

In What are the best practices for DOF stacking? I noticed a mention of a "focusing rail". I've never heard of such device. What is it, and in what circumstances is it useful?
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 ...
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 ...
15
votes
3answers
3k views

Can software auto-detect image focus?

I was wondering if there was any photo management software out there that could auto detect and "rate" images on how in focus they are. This comes up for me quite commonly when i am looking through a ...
15
votes
1answer
3k views

What is focus throw?

This answer to an earlier question of mine about manual focus lenses uses the term "focus throw". Exactly what does that mean? Why do manual focus lenses have more of it than auto focus lenses?
14
votes
3answers
2k views

Why does using a tilt-shift lens make things look miniature?

This question isn't so much about how to achieve the effect of making a scene look like it's modelled in miniature, but why tilting the focal plane creates the effect. What is it about photographing ...
14
votes
1answer
8k views

What do “Frontfocus” and “Backfocus” mean?

I've read those terms in a couple of lens reviews, and not even Wikipedia has an article about it. So my questions are: What is back/frontfocus? What causes back/frontfocus? Is there any preventive ...
13
votes
7answers
998 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
4k views

How does changing focal length affect depth of field?

I'm curious about how my "area of acceptable focus" changes when the focal length of the lens I'm using changes as I zoom (or switch lenses). In particular, I'd like to know how the front & back ...
13
votes
7answers
641 views

How do I get proper focus when photographing lightning strikes?

I've been lucky to have the opportunity to photograph several large thunderstorms in Colorado recently, however I ran into a couple issues. The first issue I've run into is getting proper focus. As a ...
13
votes
1answer
11k 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 ...
12
votes
4answers
1k views

How do you use the different autofocus points on your DSLR?

My Nikon D300 has quite a few autofocus points. There's a button I can operate with my thumb to change the autofocus point but I find that quite difficult to use. So I almost exclusively use the ...
12
votes
4answers
814 views

How close can a lens focus?

From my understanding, if you want to do some macro photography it is better to have a lens that can focus when it is really close to the subject. Sometimes people buy extension tubes to help them ...
12
votes
6answers
2k views

How do I set the focus in long exposure night sky shots?

I want to catch a good long exposure (5 - 15 seconds) shot of the International Space Station in the night sky as it passes over my city. Setting the ISO higher (say, to 100) and the exposure time is ...
12
votes
2answers
727 views

Does a crop sensor affect closest focusing distance? Why does it not affect focal length in EXIF data?

Since I am considering to buy the Nikkor 105mm micro VR, I wondered if the cropped sensor does affect the closest focusing distance of 0.31m? Thinking about this, the following additional (and ...
12
votes
1answer
4k 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 ...
12
votes
4answers
1k views

How do you manually focus accurately without a focusing screen?

I have a Canon 1000D and it doesn't come with a focusing screen. Sometimes my camera cannot focus in low-light. I'd like to manually focus, but without a focusing screen I haven't been able to do it ...
11
votes
4answers
2k views

In food photography (using a nifty fifty lens) how can I make my food shot more in focus and not blurry?

I've recently purchased a "nifty fifty" lens for my food photography. I've noticed that when I'm taking photos of my food, I just can't seem to get the focus down. For example, when I get my shot ...
11
votes
6answers
6k 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, ...
11
votes
3answers
1k views

How can I repair missed focus in a valuable photo?

The subject in my photo isn't properly focused. I can't take it again because this activity documentation photo can't be redone. I've tried many solutions such as using shadow/highlight in Photoshop, ...
11
votes
5answers
8k views

What is “infinity focus”?

I have been reading a bit about astrophotography and the term infinity focus keeps coming up. What is infinity focus and how do you set the camera to infinity focus?
11
votes
4answers
287 views

Where to focus when shooting landscapes?

When I am shooting landscapes, where (at what point) should I focus when using Auto Focus? Or if I am shooting the lit up skyline of the city, what should be my focus point? The reason I ask is that ...
10
votes
7answers
2k views

How can I get perfect sharpness when shooting still art?

I've been trying to shoot some marble sculpture that are well lit on a studio wall. The photos are coming out well and perfectly useable.. but I'm striving for something better. My issue is with ...
10
votes
6answers
1k views

How to micro-adjust distance for focusing in macro photography?

I'd like to take macro photos, but I have a problem with the focus. I put the object on a (light) table, I put my camera on my tripod and take a few shots. Since the depth of field is very small ...
10
votes
3answers
618 views

Focussing on a mirror image

When I take photographs of a subject reflected by a surface (water, mirror, glass) I notice that the focussing distance is not the distance from my camera to the surface, but mostly it is close to ...
10
votes
2answers
2k views

Is it possible to measure distance to an object by adjusting the focus?

This is maybe not a 100% on topic photography, but I couldn't find a better stackexchange site to post this on and maybe you guys can help me out. I have a camera that takes pictures of a production ...
9
votes
7answers
427 views

Focusing an entry-level DSLR

I like really really sharp photos. Even with a prime lens, I seem to be able to do noticeably better with my 450D by manually focusing using live view at maximum zoom than by using auto focus (even ...
9
votes
1answer
253 views

How can I achieve an effect in still photography that's analogous to a cinematographic effect?

I don't know how it's achieved or what it's called, but occasionally in a movie I see an effect in which the perspective of the scene is modified in such a way that the objects that are further away ...
9
votes
1answer
3k views

What is the difference between depth of field and depth of focus?

Reading this answer I realized that I didn't know the difference between the two depths (of field and focus). Browsing related questions didn't reduce the blur (!) between the two... Wikipedia ...
8
votes
5answers
491 views

Heavy colour saturation on night photos with new lens? Is this normal

I have a Canon 550D and bought a Sigma 17-70mm lens to upgrade from the 18-55mm lens kit. I decided to go out and try the new lens with some night shots. To be honest, the results were bad. I used a ...
8
votes
5answers
417 views

Are there DSLR lenses that don't allow for manual focus?

I am looking into getting a Nikon soon (either a D3100 or a D5100). One of the reasons that I am upgrading from a point and shoot is because I want to have more control over the camera's functions. In ...