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Cameras and Lenses

ciechanow.ski

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Re: Cameras and Lenses

#121

Post by sillysaurusx »

whatshisface wrote: post #112
daralthus wrote: post #109

The only thing better than a pinhole camera is a pinhole camera with multiple holes. Let me explain: When you have two holes (apertures), their images would likely overlap (depending on the arrangement). Imagine you took two photos from a few millimetres apart to the left and to the right, then you superimposed them. Some areas would look ok (as both views saw the same distant object) and some would be less ok (of ob…

> That "infinitely many overlaps" I was talking about happens with lenses too and is essentially a convolution where you convolve the image with itself (actually many different perspectives of itself if I am correct). Which is just the Fourier transform. That statement is a bit muddled, let me unpack it. The infinitely many overlaps thing can be expressed mathematically as the convolution of the image with a function…

The diffraction bands are approximately the Fourier transform of the slit function.

Is this correct from a physics standpoint? Feynman had a lot to say about light in his book (QED https://www.amazon.com/QED-Strange-Theory-Light-Matter/dp/06...) and never framed it this way. At one point he remarked that the explanations in the book were related to diffraction, and the explanation there was very different from the Fourier transform.

Re: Cameras and Lenses

#122

Post by daralthus »

codetrotter wrote: post #120
daralthus wrote: post #109

The only thing better than a pinhole camera is a pinhole camera with multiple holes. Let me explain: When you have two holes (apertures), their images would likely overlap (depending on the arrangement). Imagine you took two photos from a few millimetres apart to the left and to the right, then you superimposed them. Some areas would look ok (as both views saw the same distant object) and some would be less ok (of ob…

> captures depth information and you can use it for 3d reconstruction, refocusing etc That’s crazy cool! Got any good links for reading about how to do those things that way; 3d reconstruct and refocus?

Here's a paper on depth: http://groups.csail.mit.edu/graphics/CodedAperture/

Stanford has a class on computational imaging: http://stanford.edu/class/ee367/

I think these slides should give you a pointer to enough papers to fill a lifetime: https://web.stanford.edu/class/ee367/slides/lecture9.pdf

Georgia Tech also has a class, that's on youtube and Udacity: https://www.udacity.com/course/computational-photography--ud...

Re: Cameras and Lenses

#123

Post by StavrosK »

lb1lf wrote: post #60
bboozzoo wrote: post #59

Earlier quoted context omitted.

Actually being Polish I can say it is correct, at least for the cases mentioned (also correct for suffix -cki). However it is true that there are surnames that do not follow this particular inflection scheme. Keep in mind that Poles are likely to use a single, male variant of the surname, rather than explain the intricacies of inflection in the Polish language.

-A former girlfriend is of a Russian emigré family; she always got a chuckle out of Norwegians' inability to understand the concept of inflection. Her father as a matter of course got letters from all her leisure activities, school &c addressed to 'Mr. Yuri ----skaia'. - as her last name was ----skaia, obviously his would be, too. At least for us inflectionally challenged Norwegians.

Basically the same as "Miss John Doe".

Re: Cameras and Lenses

#124

Post by StavrosK »

baq wrote: post #95
echelon wrote: post #75

Earlier quoted context omitted.

I'm still going to use they/them because a name doesn't necessarily match with one's gender.

language 1 extracts gender to a separate word. language 2 embeds gender in the word itself. names are words. it's a lose-lose situation: native speakers of language 2 will look at what you wrote and cringe or just assume you're ignorant. they won't get the point you're trying to make, null, nada, 0% chance. source: i'm a native speaker of language 2.

Yep. "Greek is gendered, the gender is embedded into the words". Sure, but I can speak whole normal sentences without referring to gender at all, something like "went to the supermarket and bought x y z, then did a, b and c and came back".

You can talk about someone at length without mentioning their gender once.

Re: Cameras and Lenses

#125

Post by CliffStoll »

whatshisface wrote: post #112
daralthus wrote: post #109

The only thing better than a pinhole camera is a pinhole camera with multiple holes. Let me explain: When you have two holes (apertures), their images would likely overlap (depending on the arrangement). Imagine you took two photos from a few millimetres apart to the left and to the right, then you superimposed them. Some areas would look ok (as both views saw the same distant object) and some would be less ok (of ob…

> That "infinitely many overlaps" I was talking about happens with lenses too and is essentially a convolution where you convolve the image with itself (actually many different perspectives of itself if I am correct). Which is just the Fourier transform. That statement is a bit muddled, let me unpack it. The infinitely many overlaps thing can be expressed mathematically as the convolution of the image with a function…

Indeed! We like to think of light as photons, traveling in rays in straight lines. That's geometric optics and works great for most purposes in photography.

Physical optics takes into account the wave nature of light. This becomes important when the size of the lens becomes small (eg pinholes) ... there's diffraction around edges and pixels receive contributions from many points in space.

Geometric optics lets you model using ray-tracing, reflections, and Snell's law refraction.

Physical optics uses tools such as Fourier transforms, convolutions, and sinc functions.

Understanding a simple lens system? Geometric optics is your friend. Building an astronomical telescope? Check into physical optics.

Re: Cameras and Lenses

#126

Post by codetrotter »

daralthus wrote: post #122
codetrotter wrote: post #120

Earlier quoted context omitted.

> captures depth information and you can use it for 3d reconstruction, refocusing etc That’s crazy cool! Got any good links for reading about how to do those things that way; 3d reconstruct and refocus?

Here's a paper on depth: http://groups.csail.mit.edu/graphics/CodedAperture/ Stanford has a class on computational imaging: http://stanford.edu/class/ee367/ I think these slides should give you a pointer to enough papers to fill a lifetime: https://web.stanford.edu/class/ee367/slides/lecture9.pdf Georgia Tech also has a class, that's on youtube and Udacity: https://www.udacity.com/course/computational-photography--ud…

Thank you :)

Re: Cameras and Lenses

#127

Post by sudosysgen »

foo_barrio wrote: post #90
dTal wrote: post #74

Earlier quoted context omitted.

A large lens captures information over an area, and so to a certain extent can "see around" out of focus objects. A selective blur of a fully focused scene captured from a single viewpoint (i.e. a small lens) can only approximate this effect, because it simply doesn't have access to the same information. Even with a perfect depth map, you still don't know what's behind occluded objects.

If instead of resolving points of light on the image sensor, you use a group of pixels to resolve an entire tiny image you can effectively also see around things. You end up with a picture of many small sections of the large image each at a different angle. The image on the far left of the image would see a different angle than the image on the far right. This is exactly what the Lytro camera did and it's why you can…

Well yes but you're still going to need a sensor as large as the aperture of the lens you want to simulate, which makes it a non-starter for phones.

Re: Cameras and Lenses

#129

Post by kepler1 »

echelon wrote: post #79
kepler1 wrote: post #20

The site is the work of a guy, "him", and "his" work. We don't have to guess and say "them" and "their" work.

> The site is the work of a guy, "him", and "his" work. We don't have to guess and say "them" and "their" work. Assumptions are presumptuous and harmful. Everyone is a they/them until otherwise stated. These are extremely useful pronouns. You're a they/them. Calm down. You seem to be overly attached to regressive labels. I don't know what drives this in you, but the universe is burning and people just want to be happ…

I'll share something with you.

The level of consideration you have for people who are no more than 1% of the population is admirable. Very admirable, in comparison with the actual large problems that I'm sure you pay 0% attention to each day, and do make assumptions about. So very admirable that you go out of your way to bring this to the level of everyone having to select a pronoun in their dropdown menu because you feel morally superior for doing this.

Extremely useful. I'm sure you live among people who are 50% transgendered and cannot tell the difference between an man and woman with every person you come across.

Is it any wonder that most of the country feels you and such people are out of touch with the needs of the world, and vote in a backlash against you?

Re: Cameras and Lenses

#130

Post by kepler1 »

echelon wrote: post #82
h_spacer wrote: post #78

Earlier quoted context omitted.

Sorry to hear that you hold other cultures in such low regard.

Culture and gender aren't linked. Does culture tell you if someone's gender, sexual preferences, what kind of car they drive, whether or not they're a furry, what god(s) they do or do not believe in, etc.? Don't put people in boxes based on your limited world view. Think about the limit. When we're uploaded to the matrix, you'll finally be able to be whatever gender you want to be without fear for the stupid stigmas…

What a hypocrite -- feel free to let people be who they are, as long as I can force you to call them a word I want.
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