Digital Question:

[PhoenixRising]

Okay, I understand, in principle, how 'analog' film works. The shutter opens, and the image is burned onto the negative.

Right?

So how does that work on a digital camera? It's one of those things that I would like to know, if anyone knows.

Thanks!

[kcfoxie]

um well my general understanding is the shutter opens and the image is captured by a light sensitive device that's known as the CCD... I don't know what CCD stands for. The CCD, and the quality of it, will then digitize what it "sees" and saves it as a file on the camera's card. The better the CCD the more megapixels and the better the color, quality, etc.

[Steinola]

CCD stands for "Charge Coupled Device".

Think of the CCD as a series of really tiny cups, all lined up in a grid. As light is let into the camera, each of those cups begins to "fill up" to varying amounts depending on how much (and what color) light is captured in that precise portion of the frame.

The CCD then measures how much is in each cup to come up with a digital value, which is saved to your memory card.
The "Charged" in CCD refers to the static charge it creates to contain the light electrons. This is why, eventually, your CCD will collect dust (faster on a DSLR than a point-and-shoot... because you're essentially exposing the CCD to dust every time you remove the lens), and, hence, your pictures will begin to get "fuzzy" (which is why, unless you know what you're doing and know how to clean a CCD - not an easy process because they are quite delicate - you want to stay away from used digital cameras... since they'll already have dust on them, and you'll have the much less time before it begins to affect your photos).

More megapixels will generally mean that the CCD has more "cups" in the grid... though there are a couple of digital cameras out that "recycle" the CCD to elevate their megapixel value (the CCD analyzes the upper-left quandrant of the frame, for instance, calculates that value, empties all the cups, then analyzes the upper-right quandrant of the same frame, calculates that value, adds it to the first, and so on). Recycling the CCD lowers the cost of the camera, because it reduces the complexity and precision required in the chip (fewer "cups" = less cost)... but of course it takes 4 times as long (or more) to capture the picture.

If your camera has a "histogram" feature (your EOS certainly should), the histogram is a graphic representation of how much each of your CCD's cups were filled up for any given picture, in order from dark to light.

[PhoenixRising]

Originally Posted by Steinola

CCD stands for "Charge Coupled Device".

Think of the CCD as a series of really tiny cups, all lined up in a grid. As light is let into the camera, each of those cups begins to "fill up" to varying amounts depending on how much (and what color) light is captured in that precise portion of the frame.

The CCD then measures how much is in each cup to come up with a digital value, which is saved to your memory card.
The "Charged" in CCD refers to the static charge it creates to contain the light electrons. This is why, eventually, your CCD will collect dust (faster on a DSLR than a point-and-shoot... because you're essentially exposing the CCD to dust every time you remove the lens), and, hence, your pictures will begin to get "fuzzy" (which is why, unless you know what you're doing and know how to clean a CCD - not an easy process because they are quite delicate - you want to stay away from used digital cameras... since they'll already have dust on them, and you'll have the much less time before it begins to affect your photos).

More megapixels will generally mean that the CCD has more "cups" in the grid... though there are a couple of digital cameras out that "recycle" the CCD to elevate their megapixel value (the CCD analyzes the upper-left quandrant of the frame, for instance, calculates that value, empties all the cups, then analyzes the upper-right quandrant of the same frame, calculates that value, adds it to the first, and so on). Recycling the CCD lowers the cost of the camera, because it reduces the complexity and precision required in the chip (fewer "cups" = less cost)... but of course it takes 4 times as long (or more) to capture the picture.

If your camera has a "histogram" feature (your EOS certainly should), the histogram is a graphic representation of how much each of your CCD's cups were filled up for any given picture, in order from dark to light.

Thanks!

Is it true, it's a bit like a reverse LED? Or is that too simple?

[Steinola]

Originally Posted by PhoenixRising

Is it true, it's a bit like a reverse LED? Or is that too simple?

Ehhh... probably too simple. I mean... it's true, the LED takes electical signals and turns them into lightwaves (photons, actually), while the CCD takes lightwaves and turns them into electrical signals. But beyond that, there's not a whole lot that's similar.

It'd been closer to say that each of the pixels in the CCD (what I called "the little cups", above) is a single reverse LED... but not quite. Saying that would be akin to saying that a toilet was a reverse water fountain. Accurate in theory, but in use they operate in completely different ways.

[kcfoxie]

Originally Posted by Steinola

Ehhh... probably too simple. I mean... it's true, the LED takes electical signals and turns them into lightwaves (photons, actually), while the CCD takes lightwaves and turns them into electrical signals. But beyond that, there's not a whole lot that's similar.

It'd been closer to say that each of the pixels in the CCD (what I called "the little cups", above) is a single reverse LED... but not quite. Saying that would be akin to saying that a toilet was a reverse water fountain. Accurate in theory, but in use they operate in completely different ways.

Quote of the year: "Saying that would be akin to saying that a toilet is a reverse water fountain."