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basic ccds :: eye vs film vs ccd

We call the wavelengths between 400-700 nm the "visible" spectrum. These wavelengths are what the human eyes are sensitive to. Visible light is commonly remembered by the anagram ROY G BIV. This stands for Red, Orange, Yellow, Green, Blue Indigo, and Violet. These colors are just light at different wavelengths that the eye interprets as different colors.

Red: 780 nm, Orange: 620 nm, Yellow: 585 nm, Green: 570 nm,
Blue: 490 nm, Indigo: 440 nm, Violet: 420 nm

This "visible" spectrum is just a small part of the wavelengths that are out there. All wavelengths are collectively known as the electromagnetic spectrum. :: More information on light and the electromagnetic spectrum ::

CCD's are able to see a much broader range of wavelengths than humans can see (Silicon:: 200-1200 nm) enabling astronomers to observe things not visible to the eye.

Another benefit of CCD's versus the human eye is the CCD's can take a long exposure. CCD's can absorb data for very long periods of time, capturing more data. Eyes can only absorb data (photons) for a short period of time, giving eyes high refresh rates. The refresh rate is the amount of times aa image is repainted or refreshed per second on a display (ie monitor, tv, eye, etc.)

Film has a different set of shortcomings in comparison with scientific CCD's. CCD cameras are up to 100 times more sensitive than film **. CCD's also have a greater dynamic range, capturing both faint and bright details in a single exposure. Film's dynamic range varies by the film speed.

CCD's also are able to save time. In order to use film for data analysis the picture first needs to be taken, then developed, then digitized, before it can be analyzed. Information from a CCD is in digital form so analyzing can happen quicker. Another benefit of CCD's is the ease of use. Retriving film from an orbiting telescope can be quite difficult.

** CCD's come in different qualities. Astronomical CCD's are higher quality than the CCD's that are in consumer digital camera. Film has a better dynamic range than most ccd's in consumer level digital camera .

visible spectrum
Visible light :: color spectrum (from left) Red, Orange, Yellow, Green, Blue, Indigo, Violet

electromagnetic spectrum
Electromagnetic Spectrum
The visible spectrum is a very small part of the entire wavelength spectrum flash :: static


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