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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

2
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1answer
296 views

Why do some lenses focus past infinity?

On the kit 18-55 lens that came with my Nikon D5100 I have noticed that when trying to focus on infinity for shots in dark conditions (star-trails, etc) the lense tends to move past infinity out of ...
5
votes
3answers
523 views

I'm having trouble getting sharp pictures while shooting a concert from a press pass location

I am a bit of a noob when it comes to photography. But I recently got the opportunity to shoot John Mayer this past weekend in Wisconsin. Upon getting home, I noticed the pictures weren't as sharp ...
2
votes
2answers
482 views

What is the difference between depth of field and focal plane?

I would like to know how to address the difference between them and how relates to each other.
1
vote
1answer
98 views

Correct aperture to manage precisely blur and focus zones

There is something that bugs me about aperture... I understood that aperture will influence my picture on both light and focus zone. Now when taking a picture, I find it difficult to know precisely ...
4
votes
5answers
658 views

How could I achieve stock quality sharpness?

I am using Canon 600d equipped with 18-55mm kit lens and also I bought 50mm 1.8. I am trying to take pin sharp pictures to upload them for sale.I am shooting still objects and models time to time. I ...
3
votes
3answers
1k views

Is there a webcam that can focus to infinity, for time-lapse landscapes?

Does anyone here know of a webcam (at least 720p) that has the ability to focus to infinity? At least one webcam I know of (Logitech C910) doesn't allow that. I would like to use it for time lapse ...
1
vote
1answer
2k views

How do I select a focus point on the Nikon D5000?

My Nikon D5000 has 11 selectable focus points but shamefully I don't know how to choose another point other than the center point. How can I do this? Am I misunderstanding concepts?
27
votes
4answers
35k 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?
1
vote
2answers
143 views

How do I get the entire landscape in focus? [duplicate]

According to this calculator at 16mm, my hyperfocal distance is at 0.7m at f/11. So on the safe side, if I wanted to make sure the scenic background is tack sharp I would focus at 1m or so. But now ...
-2
votes
3answers
389 views

Canon 70-200mm F4 L USM IS Focus Issues Photo All Soft?

Focus Issues Bought myself a used Canon 70-200mm F4 L USM IS Lens but as yet I've not achieved a single Sharp image list of various settings tried attempts so far and still no joy very frustrating. I ...
4
votes
3answers
316 views

How Does Focus Differ Above and Below Water?

While I am trying to figure out what I need for split-underwater photography, an interesting fact came to light: A lens focuses at different distances in air than underwater. How is the focus ...
3
votes
5answers
213 views

How do I get more in focus when aperture is already quite small?

When doing a product shot like this, how do I get more in focus when the aperture is already so small. I don't want to get any smaller for the risk of introducing significant diffraction. Note the ...
0
votes
1answer
53 views

Can I remove the tiny amount of wiggle in the focus ring of my brand new lens?

I just purchased a Samyang 24mm T1.5 lens and the focus ring is not 100% solid and smooth, there is a tiny amount of give in the vertical direction (perpindicular to the horizontal direction the ring ...
2
votes
3answers
258 views

How to correctly focus on the background person in a shot?

I tried to take some portraits of my sister-in and her fiance earlier in a sunny, green park. I took a few pictures where the fiance is closest to me but turning to look at his wife-to-be who is ...
4
votes
3answers
154 views

How can I defocus part of an image in-camera separate from depth of field effects?

What physical tools (lenses/filters/etc) can be used to blur a part of an image whilst taking the photo. (I don't mean software filters in post-processing, and I want to blur selective areas ...
1
vote
3answers
4k 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
446 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
314 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
974 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
votes
5answers
7k 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?
6
votes
2answers
2k views

How can I take a photo with everything in focus with my DSLR?

I am quite new to DSLRs and one of the first things I noticed was the incredible focus points and depth that you can achieve. That is great in a lot of scenarios, but not in all. When filming a ...
4
votes
2answers
2k 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
452 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
294 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
882 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
559 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
135 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
214 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), ...
12
votes
1answer
9k 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
vote
0answers
29 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
194 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 ...
10
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 ...
5
votes
4answers
1k 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
119 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 ...
25
votes
13answers
6k 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 ...
21
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
167 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
179 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
7k 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
218 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
551 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
494 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 ...
7
votes
1answer
424 views

Why is the Canon MP-E 65mm F/2.8 Macro Lens not called a zoom?

The Canon MP-E 65mm works differently than my other macro lenses. Compare: With a standard 35mm macro, I can frame first and then adjust focus which only changes framing very slightly with. With the ...
1
vote
4answers
433 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 ...
3
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
804 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 ...