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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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4answers
627 views

Why can't my DSLR with kit lens focus on objects close to the lens?

I have a Nikon D5200 with the 18-105 kit lens. I cannot focus the objects which are 15-20 cm away from the lens. Can anyone tell me how to manipulate the settings so that i can focus those objects? ...
1
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1answer
199 views

Why do I see different focuspoint in my DSLR's viewfinder and screen with old lenses?

I've had an old completely analog Praktika SLR with a set of lenses for a few years now. The camera and lenses are still quite good but I wanted to go digital. Having recently acquired a Nikon D5200, ...
5
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1answer
108 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 ...
2
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1answer
79 views

Compensating for 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 ...
3
votes
2answers
636 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
162 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?
1
vote
1answer
189 views

How can i get AF confirmation working with Samyang 500mm f/6.3 with dandelion chip?

I've put a dandelion chip (4th gen) on my Samyang 500mm f/6.3. I shoot a Canon 6D by the way. So, that's cool now I've set the chip to return f/6.3 and I can get a correctly exposed LiveView, EXIF ...
7
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4answers
356 views

How much does a drop in temperature affect focus?

In an answer to question "What lens characteristics are important in astrophotography?" there was mentioned "If the temperature changes drastically, you may need to refocus as different materials in ...
0
votes
1answer
169 views

Canon 50mm F1.4 focus problems

I've had this lens for a couple of years, but am really struggling to get sharp pictures now. I've tried it on a 400D and a 7D and both show the same results. I had the problem with it getting stuck ...
1
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2answers
86 views

Science Fair Project Relating focus to pinhole size

I am doing a science fair project in which i want to see how the size of a pinhole effects the light diameter, and i would like to also relate this to focus and focal point. How would i do this?
1
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1answer
81 views

Tricking compact's camera autofocus

I'm trying to get some bokeh using a compact (almost premium) camera, a Nikon Coolpix p300 (although the question is general). Since the camera hasn't got a manual focus option, I'm trying to use the ...
1
vote
2answers
280 views

Why Focus Assist activating in full outdoor light on my Canon EOS Rebel?

Trying to understand why the focus assist feature is activating in full outdoor light on a sunny day. I have a Canon EOS Rebel T-3. Recently, the 18-55 stock lens was replaced free by Canon. Since I ...
13
votes
4answers
437 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 ...
9
votes
1answer
196 views

Is the focus plane of a fisheye lens inherently curved?

After shooting of a fisheye lens earlier this week, I noticed that what is in focus does not seem to lie on a flat plane as it would for a rectilinear lens. Now, I am aware that lenses usually exhibit ...
4
votes
5answers
282 views

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

The title pretty much says what I want to ask.
0
votes
2answers
249 views

how to select a proper aperture for 50mm portrait lens? [duplicate]

I am using 50 mm 1.8 potrait lens with my canon 600D. But when i take a portrait with f1.8 on Av mode using autofocus, only subjects eyes are sharp and rest of the other face is slightly blurry. How ...
0
votes
2answers
58 views

What (and why) are the differences for AF between viewfinder and LiveView [duplicate]

I find that viewfinder never beeps to confirm focus. It also is much quicker (~0.5s) but sometimes jumps around constantly and never settles to a focus point. LiveView probably gets less light for ...
2
votes
2answers
154 views

What would appear on polaroid film exposed without a lens?

I am trying to get a better understanding how lenses & focusing works. Let's say that I am standing in a completely dark room holding a unexposed polaroid film, and turn on a TV in the other ...
1
vote
2answers
287 views

Help me understand effective f-number

If I set a lens to, say, f/2 but my focus is set to its closest point, my effective f-number won't be f/2 any more but it will be higher by a factor that depends on focal length, image magnification ...
2
votes
3answers
398 views

How does autofocus point selection relate to manual focus?

Every lens I have comes with an auto-focus / manual focus switch. How should it be used if I am shooting on AV mode? If I were to select one of the focus points, do I need to have the lens on ...
2
votes
2answers
302 views

What factors determine the size of focus step done with remote shooting?

When a DSLR camera is used for remote shooting, corresponding software usually provides very simple way to change focus position: small, medium and large steps forward or backward. This is how it ...
0
votes
1answer
229 views

Canon lens FD 50mm 1:1.4 with Canon Rebel T3i - no focus

I am trying to use an old FD 50mm lens with my Rebel T3i camera but cant get focus. Is there any configuration on the camera I havo to make or it just don't work at all? Thanks!
4
votes
3answers
309 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 ...
10
votes
1answer
742 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
880 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
2k 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
100 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 ...
1
vote
2answers
159 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
604 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 ...
0
votes
1answer
67 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 ...
3
votes
5answers
329 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 ...
4
votes
5answers
851 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
3answers
177 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 ...
2
votes
3answers
357 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
516 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 ...
1
vote
3answers
6k 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 ...
5
votes
2answers
652 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
405 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 ...
3
votes
1answer
2k 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 ...
3
votes
4answers
32k 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
1answer
687 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
4k 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 ...
1
vote
2answers
402 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 ...
6
votes
1answer
726 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
139 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
253 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), ...
3
votes
2answers
4k 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 ...
1
vote
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
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 ...
2
votes
5answers
245 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 ...