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by Aditya

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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

7
votes
4answers
302 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
144 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
vote
2answers
72 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?
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 ...
2
votes
2answers
141 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
1answer
77 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 ...
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 ...
8
votes
1answer
156 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
259 views

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

The title pretty much says what I want to ask.
9
votes
1answer
4k 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 ...
0
votes
2answers
171 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
0answers
31 views

Focus point plugin for Lightroom [duplicate]

I would like to see where the focus is in my pictures (in post). My understanding is that LR does not provide such functionality. Is there a plugin available?
0
votes
2answers
53 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 ...
1
vote
2answers
246 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 ...
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 ...
5
votes
3answers
297 views

How can I increase depth of field when photographing through a microscope?

I was photographing a small beetle and ran into the problem that it was just 0.5 inches long, and the macro setting on my camera failed to produce a sufficiently detailed and crisp image. Therefore I ...
2
votes
2answers
225 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
181 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
218 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 ...
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 ...
3
votes
4answers
22k 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
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?
2
votes
1answer
381 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 ...
2
votes
2answers
875 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
737 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 ...
2
votes
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?
28
votes
4answers
40k 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
155 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
507 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
391 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
263 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
62 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
293 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
164 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
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
542 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
355 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
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?
6
votes
2answers
3k 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 ...
5
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
551 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
339 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
626 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 ...