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45 votes

Why do stars appear as circles, not points?

Whenever light passes a boundary, it diffracts, or bends, due to the wavelike property of light interacting with that boundary. An aperture in an optical system, typically circular or circle-like, is ...
scottbb's user avatar
  • 32.8k
40 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 ...
Michael C's user avatar
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28 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 ...
scottbb's user avatar
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28 votes
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Why is the hole in a pinhole camera usually a circle?

From Wikipedia's Pinhole camera article, The best pinhole is perfectly round (since irregularities cause higher-order diffraction effects), and in an extremely thin piece of material. Industrially ...
scottbb's user avatar
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22 votes
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Why is my large format lens so much smaller (in length) than my 35mm-format lens?

The focal length is the distance from the (theoretical) center of the lens to the image plane. On the large format camera, there's a lot more camera between the lens and the film. The lenses are also ...
mattdm's user avatar
  • 143k
22 votes

Is a two-prime lens possible? E.g. 35mm and 50mm

Yes, it is possible and a "Lens Turret" is one way of accomplishing it. It was very common to use a "Lens Turret" on film and movie cameras in the 1950's before zoom lenses became practical. Source:...
Mike Sowsun's user avatar
  • 12.3k
22 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 ...
Alan Marcus's user avatar
  • 39.3k
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 ...
Michael C's user avatar
  • 175k
20 votes
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Why do prime lenses have multiple lens elements?

Single lenses with real thickness refract the different wavelengths of light at slightly different angles. For anywhere other than the exact optical center of the lens, this causes a prismatic effect ...
Michael C's user avatar
  • 175k
18 votes
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How to choose a good smartphone if the top priority of the user is photography?

If you're on a tight budget and want to get the best "bang for the buck" you need to select the phone that has a camera with strengths in the areas you need them the most while letting go of other ...
Michael C's user avatar
  • 175k
17 votes
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Why doesn't an extension tube "crop" the picture?

The extension tube does change the field of view. Specifically, it enlarges the image circle size at the sensor/film plane. Light as it is projected by the rear of the lens onto the film/sensor plane ...
Michael C's user avatar
  • 175k
15 votes

How can I test that the image is inverted in a pinhole camera?

Replace the back wall of the camera with a sheet of tracing paper, ground glass (or similar translucent material) and observe the resolved image from behind the camera. You may need a dark sheet over ...
db9dreamer's user avatar
  • 1,242
15 votes

How do manufacturers get to high (83x) zoom levels on hybrid cameras?

I think the use of the term 83X while true, is most misleading. The Coolpix does a remarkable job when it comes to its optical range which is 83X. This is actually called the zoom range. The math is: ...
Alan Marcus's user avatar
  • 39.3k
14 votes

What is the farthest a camera can see?

If you simply want visual examples with commonly available lenses and resolutions the webpage: "Guide to Identifying or Recognizing a Face: Resolution, Focal length, and Megapixels" has a number of ...
Rob's user avatar
  • 1,813
13 votes
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What's the opposite of a fisheye lens?

The opposite of a fisheye is a rectilinear lens. You probably did not find one because your definition is wrong. Distortion of a fisheye lenses is not barrel distortion, it is that a different ...
Itai's user avatar
  • 103k
12 votes
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Categorization of 14mm lens as rectilinear?

Unlike most other digital cameras, Panasonic micro four-thirds cameras record lens correction information (distortion and CA, iirc) into the EXIF information of their RAW files (and will bake in the ...
inkista's user avatar
  • 52.2k
12 votes

Why do mirrors give less sharpness, gamut, and contrast than lenses?

Mirrors are better than lenses in that they are inherently free of chromatic aberrations, and are reflective over very wide spectral bandwidths. For these reasons, they are very attractive design ...
Brandon Dube's user avatar
  • 2,445
12 votes
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What is the difference between perspective distortion and barrel or pincushion distortion?

Perspective is determined by the position of the camera relative to the scene. When a camera position produces a perspective that makes an object or scene look different than we might expect it to ...
Michael C's user avatar
  • 175k
11 votes
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Is a two-prime lens possible? E.g. 35mm and 50mm

Yes it is technically possible. The question is whether this will have practically same limitations as a zoom or not. There are two objectives from Leica with stepped focal length adjustment: the 16-...
Euri Pinhollow's user avatar
11 votes
Accepted

What can cause double-vision effect in slightly out of focus areas?

A cheap filter (uncoated or poor coatings) can reflect some of the light which is always reflected off of the front element surfaces. The primary reflection (blue in the drawing) will be stronger than ...
Steven Kersting's user avatar
10 votes

What happens if anti-reflective coating is fully ruined or removed from lens' most outer surface?

Up until the late 1940s and into the 1950s, camera lenses didn't have coatings. The result was much higher incidence of lens flare and reduced contrast in the presence of bright light sources. ...
osullic's user avatar
  • 12.5k
10 votes

Is a two-prime lens possible? E.g. 35mm and 50mm

It is possible and Canon has done it, although in a different way than you'd expect - their EF 200-400mm f/4L IS USM Extender 1.4x. It's a zoom lens with a built-in teleconverter that could be toggled ...
K. Minkov's user avatar
  • 2,055
10 votes
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Are there any 24-70 2.8 lens with no length change in zooming?

You need to look for a lens that uses internal zoom so that the length of the lens will not change during zooming. You also want a lens with internal focusing so that the length of the lens doesn't ...
Michael C's user avatar
  • 175k
10 votes

What's the opposite of a fisheye lens?

A fisheye lens isn't designed to have extreme barrel distortion -- the distortion is the result of trying to map a sphere onto a plane. A regular lens follows the equation ...
Brandon Dube's user avatar
  • 2,445
10 votes

Why is the hole in a pinhole camera usually a circle?

The pin-hole casts (projects) tiny image circles on the back wall of the camera. This is also the place we position photo sensitive material so that we can replica this image on film or paper or ...
Alan Marcus's user avatar
  • 39.3k
10 votes

Why can't my custom camera body focus to far distances?

If not, do I move the lens away or closer to the optical plane to fix the problem? If the lens will focus on near subjects, but not on a subject at "infinity," then that means that the lens is too ...
Solomon Slow's user avatar
9 votes
Accepted

Does sensor size impact the diffraction limit of a lens?

Does sensor size impact the diffraction limit of a lens? No. Therefore, if the sensor is larger, and the photo-sites for the same resolution can also be larger, does this influence the diffraction ...
Michael C's user avatar
  • 175k
9 votes
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Determining the size of the smallest resolvable detail for a given camera

If you want tens to hundreds of pixels per 50 micron area, you need a microscope. Based on your object size, with that resolution, you want at least 10px/50um * 3000um/50um a 600px wide view of your ...
Brandon Dube's user avatar
  • 2,445
9 votes

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

Yes, they do. This is the cause of chromatic aberration. It happens in two ways, actually. Axial chromatic aberration (also known as longitudinal CA) happens because different wavelengths focus at ...
mattdm's user avatar
  • 143k

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