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56 votes
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Why do photo cameras lose focus when you zoom, when movie or TV cameras keep it?

The effect's name is parfocality, we are speaking of parfocal lenses. Lenses that change their focus when zooming are called varifocal lenses. Like reducing focus-breathing (change in focus also ...
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51 votes

Why aren't faces sharp in my f/1.8 portraits even though I'm carefully using center-point autofocus?

You're not doing anything wrong. You're just finding the limits of the camera/lens combination you are using. The EF 50mm f/1.8 (in various versions) has been known as the "plastic fantastic" for a ...
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44 votes
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What are the best (ethical) ways to keep insect still for outdoor macro photography?

A focus rail + stacking software will help you achieve deeper depth of field. However, if you don't have a focus rail (or time to set one up), try to pick an optimal angle to capture as much of your ...
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39 votes

How can a smartphone take pictures of a landscape with everything in focus?

It's worth noting that sensor size plays a huge role in depth of field and behavior of the lens. A smartphone has a tiny camera sensor, often around 25 square mm. This gives the camera a crop factor ...
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39 votes
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Can you tell from a blurry photo if focus was too close or too far?

It depends. In many cases, it may actually be possible without any further visual aids in the picture. Many lenses, if not most, will show different longitudinal chromatic aberration in front of and ...
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39 votes
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Why can't my custom camera body focus to far distances?

If I have built my device with the correct distance between the flange and the optical plane, does this mean the (inexpensive) lens I am using is bad? If you had built your device using the proper ...
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31 votes

Can I post process this out of focus image?

Yes of course it can be post processed. It might make it “better.” But it will never make it the picture you wish it was. The good news is that there will be other snakes on other days. Plenty of ...
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29 votes
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Why is infrared light's focus point different from that of visible light?

It is for the same reason that chromatic aberration occurs at all: different wavelengths of light will bend at slightly different angles when passing through the same refractive medium such as a lens ...
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27 votes

How can I get perfect sharpness when shooting still art?

It sounds like you're doing almost everything right, but there's one detail that caught my attention: Aperture highest the lens offers. I'm assuming that this means that you are stopping the lens all ...
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27 votes

Why focus on the eye closest to the camera instead of the eye in the middle?

There's more depth of field behind the focus than in front of it. So focussing on the near eye gives you the best chance of getting the whole face in focus. If you can't do it focussed on the near eye,...
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27 votes
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Do convex lenses make parallel light rays of different wavelength converge to different points?

Do convex lenses make parallel light rays of different wavelength converge to different points? Yes. The separation of different wavelengths of light is called dispersion. Different wavelengths of ...
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23 votes
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How to reposition subject in the same place and pose in a series of images over time

Fun idea. That could be called hyperlapse. If you use a specific memory card for that project, you can always switch from viewing the first photo of the project to live view. Another option is that ...
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22 votes

Any cameras move the sensor instead of lens elements for focus?

Not a digital camera/sensor, but the Contax AX film SLR was able to move its film plane forward and back via a ceramic rail and ultrasonic motor in order to be able to autofocus the normally-manual-...
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22 votes

Is camera lens focus an exact point or a range?

There's only one distance that is in sharpest focus. Everything in front of or behind that distance is blurry. The further we move away from the focus distance, the blurrier things get. The questions ...
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21 votes
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How can I take a photo through trees but focus on an object behind the trees?

You can focus manually. To do that with the Nikon AF-S DX NIKKOR 18-55mm f/3.5-5.6G VR II supplied as the kit lens with the D3300, you need to slide the switch on the lens to M for manual focus. It's ...
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  • 2,833
21 votes

Do convex lenses make parallel light rays of different wavelength converge to different points?

Light from a far distance object, like a star, arrive at the lens, as parallel rays. As they transverse the lens, they are forced to change their direction. They bend inward, we call this refraction ...
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20 votes

How can a smartphone take pictures of a landscape with everything in focus?

If by "landscape" you mean something like this: then the answer is simple: at very large distances, depth of field is extremely large even at large apertures. That is, at any aperture if you focus at ...
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20 votes

Can you tell from a blurry photo if focus was too close or too far?

When the aperture is positioned to minimize vignetting, the bokeh shapes for objects that are too far is rotated by 180° compared with objects that are too near. (The aperture image is reflected ...
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  • 241
20 votes

How can I get sharp bird photos when the bird is further away?

Several possibilities: In the examples shown, it could be a problem with the subject. The center of the picture is a rather fuzzy plumage for the dove and sharp lines for the white-eye. Your 55-250mm ...
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  • 16.3k
18 votes

Why do we need a DOF preview button?

Hitting the DOF preview with a stopped down aperture should make it obvious: what you see can be very dim, dim enough it can be very difficult to compose and focus. That's why cameras have the lens ...
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  • 1,174
17 votes

Why is infrared light's focus point different from that of visible light?

The ideal lens would cause light beams of every color to come to a focus at the same distance from the lens. That would be the focal length of the lens when the lens is imaging at infinity (∞ as far ...
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  • 36.2k
16 votes
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Why does this lens lose focus when you zoom in but not when you zoom out?

The lens is not parfocal in either direction. What you have discovered is the difference between narrow Depth of Field (DoF) at longer focal lengths and deeper Depth of Field at wider focal lengths. ...
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16 votes
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Since it's not "focal length", what is the term for the distance at which things are in focus?

Focal length is the distance between the lens and the sensor when the subject is in focus, not the distance to the subject. The term for the distance to the subject in focus is the focus distance ...
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16 votes
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Why does wider aperture make snowflakes look bigger?

The use of a large diameter, f/3.2 aperture allowed you to set the shutter at ½ second. You captured snow as it tumbled down. The shutter speed is insufficient to freeze the falling snow. The flakes ...
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15 votes
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How to take sharper photos

The first image was shot wide open with what is essentially the lowest cost Canon lens (50mm f/1.8), in demanding low light conditions, and at ISO 1600. I'd say your results are exactly what I would ...
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14 votes
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How do disposable cameras work without exposure and focus control?

Three things: Film is relatively lenient, and exposure variations are handled in the printing. The lens has a relatively small fixed aperture and focus is set at a reasonable distance to get a lot of ...
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14 votes
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What is the best way to focus when doing night photography or astrophotography?

For focusing on stars, I suggest using a Bahtinov mask, which uses purposely-created diffraction spikes to determine correct focus. Bahtinov mask by Justin Dolske, from Flickr. CC BY-SA-2.0 This ...
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  • 31k
14 votes
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How do I diagnose the source of focus problem in a camera?

The question is extremely broad. There are a lot of questions and answers here that address particular aspects of blurry pictures. Putting all of that in one answer would be excessively long as well ...
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  • 168k
14 votes

Why focus on the eye closest to the camera instead of the eye in the middle?

Because the way human vision perceives a two dimensional representation of the three dimensional human face if the nearest eye is in focus it looks to us more like the whole face is in focus. Even if ...
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  • 168k
14 votes
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Why can't my dSLR take close-up photos?

You are just too close to your subject. Cell phone cameras and "Point and Shoot" cameras can take photos from very close distances. DSLR cameras can not. It is actually the lens that determines how ...
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