cmos vs. ccd

[Diving Dutch]

Anyone have thoughts and comments about the differences (if any) between shooting with cmos and ccd sensors? I am reading that some broadcast-quality camcorders are using cmos, and was wondering if there is any difference in quality when it comes to shooting under water, especially in low-light conditions?
Thanks.

 

[maged_mmh]

basically, CMOS consumes more power (shorter battery life); but from electronics manufacturing perspective are easier to fabricate with higher grade purity (less flaws, better control about something called doping - related to semiconductor characteristics) and CMOS has faster response time - that's why you usually find it capable of higher ISO numbers with acceptable noise level than CCDs. CCDs allows a higher pixel count though (not the effective pixel count as CMOS has higher purity) i.e. you can cram more pixels in a given area than with CMOS but on the expense of the granulation quality.
sorry if this was too technical. Hope it helps.

 

[Diving Dutch]

So I guess though, when it comes to shutter speed (rolling vs. global shutter), is there any preference when shooting video in murky waters?

As described above, how do these differences affect underwater videography? I am in the "just learning" phase, so technical or not, it's all good information.

 

[PerroneFord]

I'm sorry, this is incorrect. CMOS consumes quite a bit less power than CCD and runs far cooler. This is why you see the current crop of full 1920x1080p sensor handycams.

Or if there is another explanation I'd love to hear it, but this was described by one of the Sony product managers last year in reference to the EX1.

-P

basically, CMOS consumes more power (shorter battery life); but from electronics manufacturing perspective are easier to fabricate with higher grade purity (less flaws, better control about something called doping - related to semiconductor characteristics) and CMOS has faster response time - that's why you usually find it capable of higher ISO numbers with acceptable noise level than CCDs. CCDs allows a higher pixel count though (not the effective pixel count as CMOS has higher purity) i.e. you can cram more pixels in a given area than with CMOS but on the expense of the granulation quality.
sorry if this was too technical. Hope it helps.

 

[maged_mmh]

OK,I'll elaborate:
from electronics facts: CMOS has a threshold voltage (upon which the semiconductor starts acquiring conductivity) of 3.6 volts (logical 1 voltage level) but yes with less complicated circuitry involved-which means less current drawn total power is lower (less circuitry because in CMOS can combine both the image sensor function and image processing functions within the same integrated circuit - another proof for faster response); while for CCD it is 0.7 (the same as a diode "analog device") but you'll need at least 3 layer of different wavelength CCDs (RGB) to render the image plus a separate off board circuitry to process the 3 images from the 3 sensors and merge them together (pretty much like offset printing); hence they say total power is higher.
BUT you're not comparing apples to apples here: 1 layer of CMOS digitally encoded colors to be processed later to 3 layers of analog CCD sensors that gives direct colorspace. if you compare the single-layered CMOS with hypothetical 1 layer CCD (no practical as it will record just a single color or monochrome) then CCD is using less power.
However; if you took the sensor element as a whole then yes; Sony marketing rep surely won that battle.
you can attest that by the fact that all small P&S cameras are employing CCDs, whilst higher end dSLR majority are using CMOS.
BTW, all computers CPUs are based on CMOS.
another thing is right - thanks to highlight, it follows by default higher power=higher heat dissipation this affects your colorspace while shooting - especially obvious in the reddish colors (lower spectrum) due to a process called thermal agitation.
I included one attachement that maybe useful for you.

 

[PerroneFord]

Interestingly, nearly all high end pro video cameras shoot CCD. Very few use CMOS. There are some notable exceptions to this (like RED and the SI2K). But the Genesis, Viper, Dalsa Origin, etc., are all CCD.

I do appreciate your clarification though and it makes perfect sense.

 

[Gombessa]

I believe this has to do to great effect with the fact that CCD is a proven and mature technology, and manufacturers are used to its capabilities and limitations and have very efficient and reliable ways to handle them.

CMOS is still developing, and companies like RED have devised proprietary and complex mechanisms to handle the different limitations of that technology (e.g., fast read-out rates to eliminate rolling shutter distortions).

 

[maged_mmh]

actually there is no old & new as per se among both; they're different technologies for different applications:
CMOS: digital sensor - less pixel density per area, higher sensitivity (e.g. lower light, higher ISO, faster response...)
CCD: analog sensor that must be connected to analog-to-digital circuitry - higher pixel density, better saturation, slower (processing done over board)