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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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1answer
723 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 ...
6
votes
3answers
6k views

How can I find infinity focus on a kit lens with no markers?

I have a kit lens which has no markers. What would be a recommended way to find infinity focus on this lens? I plan to shoot objects at night -- not necessarily stars or the moon. So, adjusting the ...
6
votes
2answers
876 views

How does autofocus confirm work with manual lenses?

When I was a kid my dad had an Olympus OM10, he had a bunch of lenses for it and I remember focusing was done with a special circle in the middle of the viewfinder, where you pointed it at the thing ...
6
votes
3answers
2k 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 ...
5
votes
3answers
2k views

Are there advantages to using a viewfinder for focusing instead of using a camera's rear LCD screen?

Are there any particular advantages to using the viewfinder for focusing instead of the LCD?
5
votes
5answers
474 views

Should I refocus if I change the aperture in a DSLR?

The title pretty much says what I want to ask.
5
votes
4answers
5k 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 ...
5
votes
2answers
422 views

How is the term Gaussian blur used?

Is the term Gaussian blur used strictly in post-production, or can it also be used as a term for an out-of-focus area in your image when you-re taking the picture? I'm pretty sure that bokeh is used ...
5
votes
3answers
4k views

What's that sign with a dot and a number in the view-finder?

I have a Canon 550D and when I look through my view-finder to take photographs, it displays all the current settings inside the view-finder itself like aperture value, shutter speed, ISO etc. However,...
5
votes
1answer
1k views

How do disposable cameras work without exposure and focus control?

Before I got into photography, I used to use disposable cameras with ISO 400 film. I've gotten some decent results in various lighting, both inside and outside and at different focus distances. How do ...
5
votes
4answers
81k views

How can I fix an out-of-focus blurred photo in Photoshop?

How can I fix this picture? Somebody else took this picture and well he wasn't able to do it very well, and it's blurred. I have photoshop
5
votes
2answers
5k 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?
5
votes
1answer
1k 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 ...
5
votes
2answers
7k 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 ...
5
votes
4answers
2k views

Are there cheap or DIY focus assist solutions for the Canon 5D?

I want a better autofocus system for low light. Low light auto focus is my biggest bane. I use a 5D so the options are AF on a flash like the 430 or 580. I happen to use the Pocket Wizard TT1 so I ...
5
votes
4answers
2k views

What's the difference between holding a half-pressed shutter button and pressing the AE lock?

As I have been looking around today the AE lock button is supposed to lock in the focus and exposure settings (aperture and shutter) so that the picture can be recomposed before taken. I also believe ...
5
votes
1answer
169 views

Background warping through foreground defocus

I came across this effect the other day, and have spent the better part of the last week trying to figure out exactly what is happening. When photographing two layers, with the foreground in front of ...
5
votes
2answers
1k views

Is it possible to Zone Focus with a DSLR?

I have a Canon 1000d. Is the zone focusing technique applicable in a DSLR? If yes, how do we do it?
5
votes
2answers
1k 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 ...
5
votes
1answer
230 views

Which lenses show focus shift?

Some lenses, because of a design that includes uncorrected spherical aberration, shift their plane of focus backwards as the aperture is narrowed. This is most apparent at close focusing distances and ...
5
votes
2answers
236 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 ...
5
votes
1answer
464 views

Is it possible to get tethered focus and aperture control with any current DSLR?

I'm looking to get into some photography work and I had a couple questions. I'm quite an amateur at this, unfortunately, so I would appreciate any and all assistance! I want to be able to control the ...
5
votes
3answers
370 views

How do waterproof lenses focus underwater?

Our eyes need air in front of them to be able to focus properly, that's why when we go swimming using goggles, our surroundings are much clearer than without. So my question is, how do waterproof ...
4
votes
5answers
2k 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 ...
4
votes
2answers
591 views

What is the reference plane used when the minimum focus distance is measured?

Once you know the MFD (minimum focus distance) for a particular lens, is that the distance from the subject to the front of the lens or to the camera sensor?
4
votes
4answers
238 views

Doubt about focusing in the lens?

I usually find after blowing out my pic in computer that at one point (where I wished to focus) image is very sharp, then as I inspect the picture I see that some more part of the image either ...
4
votes
4answers
2k 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 ...
4
votes
2answers
1k views

Why do I get blurry pictures at far distances, but sharp results up close?

I took this picture: https://www.flickr.com/photos/91552641@N06/15828810701/ and if you look at the details (like the trees on the right side) they are all kinds of muddy. I had the same experience ...
4
votes
2answers
1k views

What is the meaning of having 9 focus points and how to see where they are?

Canon PowerShot SX210 IS is said to have 9 focus points. I haven't seen any setting which shows all those points on the screen or anywhere. How and what are those remaining 8 focus points used for? ...
4
votes
2answers
2k views

What might make focus points blurred/gone from viewfinder on Canon T2i after cleaning?

The red lights are all but lost in my T2i now....barely a haze of a blur. The focus points work fine, and I get the audible beep, but I have to check my focus point on the back before shooting and I'm ...
4
votes
2answers
191 views

How can I more consistently focus on the point I want?

I've had so many wonderfully composed images turn out lousy because my AF isn't as accurate as I'd like (or I don't know how to wield it). Despite using single-point AF, my focus point is often ...
4
votes
3answers
178 views

Does hyperfocal distance only apply to manual focussing?

At any given aperture and focal length, I can still focus on something near or something far away by simply touching the lcd on my dslr. Does that mean that because I may not be focussing at the ...
4
votes
2answers
188 views

Getting a completely sharp bird when it is up close

Context So I know that Depth of Field (DoF) is controlled by your f-stop (aperture opening) of the lens in question. Question Is it possible to get birds completely sharp when they are so close (8....
4
votes
1answer
240 views

How do I auto-focus an EOS M when stopped down to kill the ambient?

I'm trying to do take some portraits with two off-camera strobes. I want a dark background, so I'm using a high f-stop and high ISO to kill the ambient, relying on the strobes to light the model. But ...
4
votes
3answers
1k views

how to focus with a ND filter

I've just bought a ND3 filter (-10 stops) and was looking for recommendations on how to focus the camera. Basically many recommendations are around focusing WITHOUT the filter, then switch to manual ...
4
votes
2answers
566 views

How can I achieve well focussed and sharp images at long focal lengths?

Well I guess this is a question every newbie asks. I have a Canon 550D with the 18-135mm kit lens. I was out on a small trip in a nearby town to take some good snaps with my DSLR. I know the lens ...
4
votes
3answers
247 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 ...
4
votes
4answers
4k views

How can I make close-by objects appear as if they were much bigger?

We all know the popular Tilt Shift technique that gives objects a "miniature" look, making them appear much smaller than they actually are. I'm wondering whether it's possible to achieve the opposite ...
4
votes
2answers
177 views

Light-field shots entirely in focus?

A light field camera can be used to make shots which can be truly refocused after the shot, however if I understand the technology correctly it would be just as easy to process the "image data" in ...
4
votes
1answer
205 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 ...
4
votes
3answers
664 views

Does focal length change when I adjust the focus? [duplicate]

When I adjust the focus of my camera, in general, does this affect the focal length? I have heard that it does.
4
votes
1answer
271 views

Is the distance scale on a lens linear?

I have Nikon lenses with distance scales on them so I can set the lenses to the hyperfocal distance when I need. Say now the focal length is 28mm and the aperture is f/16. The corresponding ...
4
votes
3answers
1k 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
6answers
1k views

Why don't we focus at the nearest hyperfocal distance to get everything in focus?

I came across this article, and it says that if we focus at a hyperfocal distance, then everything from half of hyperfocal distance to infinity will be in focus. Then why don't we set the focus ...
3
votes
2answers
262 views

Which focus mode should I use for a portrait shoot?

I have to do a portrait shoot for a friend. My camera (Pentax K-30) allows me to focus in the following modes: 1 focus point (center) 11 auto focus points 5 auto focus points I haven't yet ...
3
votes
2answers
216 views

Is there any reason you would use one-shot focus over AI-Servo?

The only one I can think of is recomposition - achieving focus and then recomposing. Are there any others? The convenience of tracking your subject seems very, very convenient - moreso than the lock ...
3
votes
4answers
133 views

Why is my subject still out of focus when it's inside the range shown by a depth of field calculator?

In a depth of field app, I entered my camera's sensor size, focal length of 50mm, aperture of f8, and focus distance of 6 feet. The app tells me that DoF is 2.1 feet, from 5.1 to 7.2 feet. I then ...
3
votes
4answers
2k views

How to avoid soft image at longest focal length with telephoto zoom lens?

I have a Tamron 70 - 300mm lens. I have noticed that the best focus I can achieve at the 300mm setting is not as sharp as the focus I usually get at a lower setting. Is this a common problem? Is there ...
3
votes
3answers
681 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 ...
3
votes
2answers
7k 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 ...