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83 votes
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Are there cameras that can photograph Wi-Fi/WLAN or mobile phone radiation?

In order to get an image, both the subject and the "camera" must be much larger than the wavelength of the light that you use for imaging. The wavelength of visible light is between approximately 400 ...
oefe's user avatar
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22 votes
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Why do polarising filters only work in one direction?

You're probably comparing a linear polariser with a circular polariser. The linear polariser is a basic filter that only passes light waves polarised in a particular direction. That works either way ...
JerryTheC's user avatar
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20 votes

Are there cameras that can photograph Wi-Fi/WLAN or mobile phone radiation?

I disagree with the answer with many upvotes. Physical lengths can be "swindled" in a number of ways and theoretically it would be possible to build a portable camera that snaps images of a very tiny ...
Noldor130884's user avatar
19 votes
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How do apertures which seem too large to physically fit work?

Your observations of the lens leads you to both a correct, and incorrect, conclusion. Correct: the aperture (i.e., mechanical iris) of the lens is substantially smaller than the 10 cm it supposedly ...
scottbb's user avatar
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18 votes
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Since the speed of light is so high, why does shutter speed even matter?

why does shutter speed modify picture sharpness/detail? Why do pictures get darker with faster shutter speeds, and brighter with slower shutter speeds? These things happen because the light sensor in ...
Caleb's user avatar
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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
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12 votes
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What's the actual physics of diffusion filters?

I read online that diffusion filters do not add data as the entirety of the effect can be recreated in post with more flexibility. Yes and no. But in practice mostly no. Yes, in principle, the ...
Ilmari Karonen's user avatar
10 votes
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Does a sensor count the number of photons that hits it?

Your link discusses how a CCD (charge coupled device) image sensor works. Note, CCDs have applications besides images sensors, but the vast majority of CCDs are used as image sensors, and that is the ...
Matt's user avatar
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8 votes
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What is the flame-like pattern detected in this image near the hammer of a metal worker?

What you're seeing is smoke what I am assuming is coming from the hot metal as the worker hit it. This smoke hit a light beam (probably coming from a window somewhere in the room) and was lit up, ...
timvrhn's user avatar
  • 2,704
8 votes

What's the actual physics of diffusion filters?

Diffusion filters cause a portion of the light to refract/bend by creating some kind of obstruction. The amount (percentage) of the light that is scattered is indicated by the filter's strength rating....
Steven Kersting's user avatar
8 votes
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How (the heck) did NASA photographer Joel Kowsky take this amazing photograph of the International Space Station transiting the Sun?

I've actually done this myself. The first time I was not successful. The second time I was successful. Considerations There are a few things that go into this. Planning -- finding a transit near ...
Tim Campbell's user avatar
  • 3,897
7 votes

Are there cameras that can photograph Wi-Fi/WLAN or mobile phone radiation?

Sort of. Not a "camera", but a computational imaging technique. We explore the feasibility of achieving computational imaging using Wi-Fi signals. To achieve this, we leverage multi-path ...
pjc50's user avatar
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7 votes
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How much of digital sensor noise is thermal?

It depends: On the sensor design, the ISO setting selected, the length of exposure, the intensity of the light entering the camera, etc. Thermal noise can be anywhere from almost none of the noise in ...
Michael C's user avatar
  • 174k
7 votes

Does a sensor count the number of photons that hits it?

No, you won't obtain the photon count directly. Also, a camera sensor has noise, not just from photon counting but also from electrical circuits. Also, a DSLR has a color filter on top of the pixels, ...
juhist's user avatar
  • 6,588
6 votes

Since the speed of light is so high, why does shutter speed even matter?

No, it's a photography question alright. But I assume that by "clarity" you mean "sharpness", otherwise the question makes no sense. If your object is 30 m away, light from it will reach the sensor ...
stevenvh's user avatar
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6 votes
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Polarization and Rainbows

The obvious answer is that the light from a rainbow, or at least the portion that is fitting in your viewfinder at the time you are rotating the polarizer, is all polarized in the same direction.¹ ...
Michael C's user avatar
  • 174k
5 votes

Why do polarising filters only work in one direction?

The digital camera sports automation that adjusts exposure and focus. These mechanisms are likely dependent on semi-silvered mirrors. These work like mirrored sunglasses; they pass some light and ...
Alan Marcus's user avatar
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5 votes
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How do wavefronts/wavelets propogate in three dimensions, and why is this important for photography?

Okay, so, the first thing to understand is that the textbook¹ is trying to get you to understand a theory put forward by Christiaan Huygens in the late 1600s. It turns out he was (generally) right ...
mattdm's user avatar
  • 143k
5 votes

photon counting with a DSLR

Get an idea on the spectral sensitivity and quantum efficiency of your camera. The data are provided by the camera manufacturer and/or chip manufacturer. It's easier for monochrome cameras as there is ...
planetmaker's user avatar
4 votes

Why is the area in focus in front of the focus distance narrower than behind it?

Why is the area in focus in front of the focus distance narrower than behind it? It isn't. Not always. Just usually for landscape shooters using wider lenses aiming somewhere not that close. :) The ...
inkista's user avatar
  • 51.1k
4 votes

Since the speed of light is so high, why does shutter speed even matter?

You can imagine light as an electromagnetic wave, but for this question I'll use its second "state" as a (humongous) set of particles - photons. Why do pictures get darker with faster shutter ...
Crowley's user avatar
  • 1,808
4 votes
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What technology do modern flashes use to emit light?

Flashes and studio strobes use arc light: a glass tube with electrodes at both ends containing a gas that can be ionized at high voltage to produce light (e.g. Xenon). Arc lights can fire incredibly ...
the_limey's user avatar
  • 518
4 votes

Camera image in pixel to real image in meters size relation

The actual focal length if the lens depends on the focus, so you cannot even trust was is reported in the EXIF data or even the markings on the lens. If the settings are repeatable (prime lens...) ...
xenoid's user avatar
  • 20.2k
4 votes

What is the farthest a camera can see?

It depends on the lens you're using. I have a sigma 150-600mm lens on a Nikon D850 and I can safely identify people over a distance of 1.2km There is a CANON 5200mm lens, with a much longer reach: ...
Alexander von Wernherr's user avatar
3 votes
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Cross Polarization: Are linear and circular polarizers compatible?

Yes. Both of these filters exclude light that doesn't match the appropriate direction of polarization. Circular polarizing filters start with a linear polarization filter. They then also have a ...
mattdm's user avatar
  • 143k
3 votes

Polarizers: Linear vs Circular. How does it affect a photo?

A 'circular' polarizer is just a linear polarizer with a quarter-wave plate behind it that repolarizes the light in a circular kind of way. But the polarized light removed by passing through the ...
Michael C's user avatar
  • 174k
3 votes

Are there cameras that can photograph Wi-Fi/WLAN or mobile phone radiation?

Another 'sort of' answer: One possibility, more analogous to a traditional camera, is to use a stationary receiver and a strongly directional antenna. If the antenna is directed in the same way that ...
pbeentje's user avatar
  • 131
3 votes

Why is the focus distance for a mirror image further than the surface of the mirror itself?

Yes, you either get the lake (or mirror, with its beautiful carved wood frame !)) in focus, or the reflected clouds at infinity. If you want the ducks on the lake and the beautiful reflection of the ...
Benjamin Cooper's user avatar
3 votes

What is the farthest a camera can see?

I took this hand-held (or maybe having support from a flat platform but not a tripod) with Nikon D750 and Tamron 150 - 600 mm at 600 mm, f/11, 1/2000 s and ISO 1600. I didn't think of the settings too ...
NikoNyrh's user avatar
  • 131

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