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Cameras and Lenses

ciechanow.ski

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Re: Cameras and Lenses

#41

Post by miahi »

The_Colonel wrote: post #35

I have a question for the more knowledgeable: Color filters on the sensor split the light into three wavelength ranges - red, green, blue. Then photosites measure intensity of light, which means that sensor only knows that the incoming photon is "roughly green", but doesn't actually recognize its precise wavelength. So e.g. when the light is pure orange, it falls down into red wavelength range and is counted as red.…

They work exactly the same as a screen. Orange is not pure red, it is red + yellow, and yellow is red + green. So orange is red + _some_ green. The in-camera processing will render the image based on the sensor input and the known properties of the filter (think of it as a color profile, a mapping between what the sensors read and the color). And the processing includes color interpolation for each pixel, as each pixel (photosite) only has one color filter, but the resulting image pixel has all three colors; these are calculated based on the neighbor photosites.

Different sensors/cameras have different filters, and combined with the manufacturer specific post-processing this gives different cameras/manufacturers a different color rendition and feel.

Re: Cameras and Lenses

#42

Post by _ph_ »

friendly_chap wrote: post #40
The_Colonel wrote: post #35

I have a question for the more knowledgeable: Color filters on the sensor split the light into three wavelength ranges - red, green, blue. Then photosites measure intensity of light, which means that sensor only knows that the incoming photon is "roughly green", but doesn't actually recognize its precise wavelength. So e.g. when the light is pure orange, it falls down into red wavelength range and is counted as red.…

Not an expert but: orange color code is FFA500. It has red and green. I expect when orange hits the sensor, it will register as X amount of read and less than X green?

That is correct. The sensitivity of the "red" and "green" pixels overlaps in the orange light frequencies.

Re: Cameras and Lenses

#43

Post by kruxigt »

echelon wrote: post #8
Jaruzel wrote: post #7

Although I knew most of technical aspect described having immersed myself in Photography several years ago, I cannot express properly how GOOD this article is. The sliders and diagrams are brilliant for helping a layperson understand how it all works. Kudos!

You'd like their other work : https://ciechanow.ski/lights-and-shadows/ https://ciechanow.ski/gears/ https://ciechanow.ski/tesseract/ Etc. Check out the whole blog! It's amazing. These are some of the most intuitive explanations coupled with the slickest animation / demo work I've ever seen. All of that put together into crystal clear educational material is such a rare gem and requires incredible talent. Impressive…

And the articles renders so fast and so smooth on my laptop. In fact they render more smoothly and loads faster than 99% of all much much less technically advanced articles out there. Wow!

Re: Cameras and Lenses

#44

Post by The_Colonel »

_ph_ wrote: post #37
The_Colonel wrote: post #35

I have a question for the more knowledgeable: Color filters on the sensor split the light into three wavelength ranges - red, green, blue. Then photosites measure intensity of light, which means that sensor only knows that the incoming photon is "roughly green", but doesn't actually recognize its precise wavelength. So e.g. when the light is pure orange, it falls down into red wavelength range and is counted as red.…

You are right, this is a challenge. The wavelength of the light cannot be measured directly, only inferred by the intensity of the pixels with the different color filters. On the other side, most reproductions of photos are reproducing the original frequencies either. A computer screen has red, green and blue dots, which produce light at the corresponding wave lenghts. So if you have orange light, you have a signal o…

Thank you for your great explanation. The overlap was the missing piece in my mental model ...

Re: Cameras and Lenses

#46

Post by iamacyborg »

lm28469 wrote: post #34

FYI there are digital sensors which aren't using bayer filters. Some are classic sensors missing the bayer filter (leica monochrome for example) other are based on different tech like Foveon sensors [0] Many people also debayer their cameras themselves, especially in astro photography [1] [0] https://en.wikipedia.org/wiki/Foveon_X3_sensor [1] https://stargazerslounge.com/topic/166334-debayering-a-dslrs...

Fuji also use what they call an X-Trans sensor.

https://en.wikipedia.org/wiki/Fujifilm_X-Trans_sensor

Re: Cameras and Lenses

#47

Post by KineticLensman »

The_Colonel wrote: post #35

I have a question for the more knowledgeable: Color filters on the sensor split the light into three wavelength ranges - red, green, blue. Then photosites measure intensity of light, which means that sensor only knows that the incoming photon is "roughly green", but doesn't actually recognize its precise wavelength. So e.g. when the light is pure orange, it falls down into red wavelength range and is counted as red.…

>> So e.g. when the light is pure orange, it falls down into red wavelength range and is counted as red

'Pure' orange light isn't red. It has a wavelength of 590–620 nm. Red is 625–740 nm and Green is 495–570, so 'orange' is between red and green. The sensor filters each allow a range of wavelengths through. So green is triggered as well as the red filter. In RGB terms orange is 255, 127, 0, i.e. with a strong red component and a smaller green component.

White balance is computed downstream from the sensor, and is used to resolve the effect that a coloured light source creates a colour cast on objects, most noticeably on white ones. The human visual system auto-compensates for this but cameras require special processing, sometimes done using presets for different types of light (sunlight, shade, tungsten etc).

Re: Cameras and Lenses

#48

Post by zokier »

_ph_ wrote: post #37
The_Colonel wrote: post #35

I have a question for the more knowledgeable: Color filters on the sensor split the light into three wavelength ranges - red, green, blue. Then photosites measure intensity of light, which means that sensor only knows that the incoming photon is "roughly green", but doesn't actually recognize its precise wavelength. So e.g. when the light is pure orange, it falls down into red wavelength range and is counted as red.…

You are right, this is a challenge. The wavelength of the light cannot be measured directly, only inferred by the intensity of the pixels with the different color filters. On the other side, most reproductions of photos are reproducing the original frequencies either. A computer screen has red, green and blue dots, which produce light at the corresponding wave lenghts. So if you have orange light, you have a signal o…

> The wavelength of the light cannot be measured directly, only inferred by the intensity of the pixels with the different color filters.

Well, depending how you think "directly" but you can get pretty far with spectrometer, i.e. device that splits light and measures the intensity spatially to collect a spectrum. It's not impossible thought to build camera based on that principle, just need to sample the light in an array to make pixels

Re: Cameras and Lenses

#49

Post by zokier »

friendly_chap wrote: post #40
The_Colonel wrote: post #35

I have a question for the more knowledgeable: Color filters on the sensor split the light into three wavelength ranges - red, green, blue. Then photosites measure intensity of light, which means that sensor only knows that the incoming photon is "roughly green", but doesn't actually recognize its precise wavelength. So e.g. when the light is pure orange, it falls down into red wavelength range and is counted as red.…

Not an expert but: orange color code is FFA500. It has red and green. I expect when orange hits the sensor, it will register as X amount of read and less than X green?

That is in the rgb color model. In physical world, there are (almost) infinitely many different spectra that could be perceived as same "orange". It is honestly pretty amazing how well human color vision works despite that

Re: Cameras and Lenses

#50

Post by h_spacer »

franga2000 wrote: post #24
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.

But it's way less effort than checking, isn't it? The name in the footer isn't English, so it's hard to know from that and there's no about page that I could find. The Twitter profile makes it more obvious, but I only clicked on it to check because of your comment. Why bother??

Slav surnames are gendered. * ski is male, * ska is female, * sko is neutral. Using gender neutral in this case is as insulting as calling him a dog.

Other cases where using gender neutral pronouns insults everyone speaking the language is using Latinx for Latino. If you want to butcher every other languages genders like they are in English, use Latin instead - the gender neutral form of Latino in English since only the middle ages.

Hope this helps.

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