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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

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3answers
5k views

What does infinity focus mean and when should I use it?

All my lens have focus ring where at the end there's an infinity symbol. What does that mean? If I'm taking landscape shot and what everything from near to far to be in focus, do I use infinity? Or am ...
6
votes
5answers
2k views

Why is my Nikon 18-200 lens not focusing at higher focal lengths?

My Nikon 18-200 lens on a D300 camera will not focus when it is zoomed between 135mm and 200mm. Is there any tips on how to solve this besides handing it in to a photo store?
3
votes
2answers
3k 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 ...
5
votes
2answers
577 views

How can I quickly tell without testing if my lens is parfocal or varifocal?

I have read a couple of related questions, but I am curious to find out if there is a list of parfocal/varifocal lenses out there. I'm most concerned with the lenses I have and I would like to know ...
6
votes
1answer
376 views

When focusing at max zoom, focus is lost after zooming out. Is that normal?

On my Canon kit lens, I could completely zoom in, focus on the object and then zoom out to take the picture with the object still in focus. Now I have a Sigma 18-200mm (with a Canon 600D) and that ...
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, ...
3
votes
1answer
1k 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 ...
11
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5answers
9k 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?
5
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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 ...
4
votes
1answer
595 views

Do all telephoto zoom lenses backfocus on the wide angle end?

I’ve just gone through a round of testing with two telephoto zooms, on two different cameras, and both appear to have significant back focus issues at the 70mm end. I just had the Nikon 70-200 f/2.8 ...
1
vote
2answers
360 views

What does it mean for a telecentric lens to be focused to infinity?

I have a question about a telecentric lens Ive been studying (for physics research!) and was wondering if you guys could help clear some cobwebs in my head. For starters, I am simplifying the TC lens ...
2
votes
2answers
1k views

How can I get better results when manually focusing with my Nikon D7000?

For some reason I seem to have problems getting consistently well focused photographs. They are not always crystal sharp and this frustrates me. I know if I set the camera to auto, they are always ...
6
votes
1answer
648 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 ...
0
votes
2answers
138 views

What happens when you turn the objective

What happens when a photographer with an old photograph machine turns the objective clockwise or counter-clockwise? Is the lens turned too? Or does it change lens? I'm studying optics right now and ...
2
votes
2answers
237 views

Canon 50mm f/1.2 focus shift not seen yet

I know that this lens is known to exhibits focus shift if the object is less than 4 feet away within the range f/2-f/4. However, I've done quite a lot of close-up photography (mostly flowers), ...
13
votes
1answer
12k 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
30 views

How do smartphone cameras focus? [duplicate]

I'm curious, when I focus my DSLR or my pocket camera the lens moves back and forth changing the distance from the sensor. Does this really happen inside my smartphone?
2
votes
5answers
209 views

Aperture priority mode in high speed lens while photographing more than one person

I use 50mm f/1.8 lens(with Canon T3i) for portraiture. It's quite easy when only one subject is involved :Open the aperture wide, focus on the eyes(most of the times) and you get a nice portrait. How ...
12
votes
6answers
3k 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 ...
5
votes
4answers
2k views

How does a camera without hardware autofocus focus?

For e.g. an Apple external Firewire iSight does not have hardware autofocus. So how does it focus? Related questions: Does it focus to infinity? Does that mean it needs a "longer" minimum distance ...
3
votes
1answer
131 views

Does lens focus affect the appearance of sensor dust?

I know that aperture affects the appearance of dust on a camera's sensor (or, technically, the filter in front of the sensor), but does focus matter at all? Since the dust is behind the lens, I ...
26
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 ...
8
votes
5answers
1k views

Should both eyes be focused in a portrait?

I'm a hobby photographer, and I've just picked up "rules of thumb" and "tips&tricks" here and there. I have a 50mm f1.4, and I love it. But due to the extreme shallow depth of field (at f1.4), I ...
24
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 ...
1
vote
2answers
187 views

How can I take better pictures in theatre fog?

I am taking still and video photography for a film production. It is set inside a theatre that is filled with light fog. I somehow can't get sharp focus and because of the low light I can't up the ...
5
votes
2answers
183 views

Why do the Nikkor non-AI 135mm vs 50mm f/1.8 work differently when I look directly through the lens?

I recently purchased an old Nikkor 135 f/2.8 non-AI lens. Beautiful lens, but the closest focal distance is about five feet. I noticed that it will 'focus' at about 4 inches as well. If I hold the ...
6
votes
3answers
9k views

How can I get correct focus on the moon or stars with my DSLR? [duplicate]

Possible Duplicate: How to nail focus for DSLR astrophotography? I don't know if D5100 is right camera for this kind of stuff, but I would like to shoot night sky covering moon, stars and ...
2
votes
2answers
232 views

Automatic vs Manual Focus [duplicate]

Possible Duplicate: When is manual focus better than autofocus? Perhaps this question has been asked before. I understand that in some cases, automatic focus cannot be used, for example, ...
8
votes
2answers
698 views

How can I “focus peak” a photograph?

Does an application exist where I can input an image and then the application indicates what parts of the image are in focus? I imagine it as a sort of post-process focus peaking.
2
votes
1answer
587 views

Is it possible to get bokeh in cellphone photos?

I have wondered how to get some parts of the image out of focus when using smartphone cameras (or if it can even be done). Recently found out about the concept of bokeh, and am interested in ...
1
vote
4answers
460 views

Autofocus performance of different brands at night

Are there huge differences in the ability to focus in low light between different brands and models? I have a Pentax Kx with a Sigma 30mm 1.4. My problem is, that the camera's autofocus does not work ...
4
votes
2answers
2k views

What does “Flat Field Focus” mean?

Looking at lenses, specifically sigma macro lenses, I noticed that it had a ""Flat Field" front lens element". What does this mean? And how is it different to the norm?
2
votes
2answers
999 views

How to calculate the size of the image circle at infinity focus?

How can I determine the diameter of the image circle (i.e. the diagonal size of CCD required to fully utilise a telescope's optics) at near-infinity focus? I have looked around online and found this ...
8
votes
3answers
1k views

Easier ways to pre focus a distance on a lens without manual focusing meter?

In applying zone focus(focusing at particular distance in advance, before the subject comes in) to shoot a bike that will come into frame, how do I correctly focus at a particular distance with a lens ...
7
votes
5answers
3k views

Can more than one focus points be selected?

Now a days, almost every DSLR camera comes with many focal points 9, 11, 22 etc. Many of them provide us with settings to chose manual focus point while shooting images, apart from the auto-selection ...
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 ...
8
votes
5answers
500 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
4answers
5k views

What is the best auto-focus mode to use for bird photography?

Consider the image below: How would the shot be focused here? Using Auto-focus or manual? If there was a cluttered background, will auto focus detect the small bird and sharply focus on it?If manual ...
2
votes
2answers
419 views

Why is my lens focusing sound lounder than before?

I'm new to DSLR camera. I didn't mount a lens properly. The camera still allowed me to take photos, so I didn't notice the error. After I had been using it for 10 minutes I noticed my error and ...
4
votes
1answer
163 views

What factors influence whether a lens and camera combination front or back focus?

I know that sometimes a lens/body combo needs to be micro-adjusted to attain ideal focusing behavior, and that this is usually because of sample variation, but which parts of the lens and/or body are ...
1
vote
0answers
86 views

Tips to manually focus sharply with viewfinder? [duplicate]

Possible Duplicate: How does one get manual focus right with a fast-aperture lens? I feel difficult to manually focus via the view finder because of its small size.Its seems to be in good ...
2
votes
4answers
2k views

How do Canon 600D and 650D compare with respect to focus points types?

My photographic style is action, and according to a website that I read I need at least 9 focus points to get better photos. I'm considering getting a Canon EOS 650D, but it turns out that it has ...
3
votes
1answer
404 views

Why does my Canon 1000D focus only on the bottom part of an image?

I had it checked in case it needed repair, but they said they could not find a problem with it. I really need help on this one. [the process] I turn the camera on, select M mode, select the top ...
1
vote
2answers
356 views

Is there a way to use phase detection AF with live view on a Canon EOS camera?

On any of the EOS xx(x)D model that has the live view function, can the camera make focus using the AF collimators (instead of using contrast detection), as it's possible on the old Nikon D300 ? If ...
2
votes
1answer
530 views

Wide angle + macro converter

I just bought an "0.43x Super Wide Angle" converter. The converter consist of two separate parts, a wide angle (W) part and a macro (M) part. The full converter screws on the filter thread of my Sigma ...
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 ...
3
votes
2answers
443 views

How To Fix Badly Functioning Shutter Release-Button?

I have a compact Pentax OptionM10 which I bought in 2006 and sometimes shutter-release button works only when pressing it on edge and under specific angle, but mostly as I apply little pressure which ...
3
votes
2answers
698 views

All my photos were blurry

I recently did a shoot of a baby and my 6 year old son, and I got some fantastic shots that were super sharp. I then did another shoot of a 6 year old and toddler and every single photo was slightly ...
3
votes
1answer
841 views

Taking pictures with fixed/full focus camera

I have got a fixed focus, 5 MP camera with 3.3mm focal length (not sure what it means) on my phone. I want to know what's the best way to take pictures with since it's missing auto-focus feature. Is ...
0
votes
0answers
37 views

combine video frames for clarity [duplicate]

Possible Duplicate: CSI image resolution enhance: How real is it? Apologies if this isn't the best SE for this search. What might be good software, esp. opensource/freeware, to combine ...