CMOS is less noisy because it consumes less power?

crobs808 wrote in post #4273002
lol, that' doesnt really make sense. the sensor inside a cell phone camera is about 1/10th the size, and the noise there comes from basically a built in digital zoom/crop. take a 1024x768 pic with your cell phone, then a 640x480 cell phone. the 1024res is just an enlarged 640 capture..that accounts for the additional noise and blurriness on cell phone pics...phones dont exactly have a DigicIII processor in them, lol

::: connor

Ok hope this will clear it up for you.

The Title of this thread is "...CMOS is less noisy because it consumes less power..." so if this is true then CMOS in cell phone should be less noisy, But it is not. Now if you continue to read on to later posts I speculate that because Canon incorporated intergated AD convertors and Amps into the CMOS sensor they were able to use a less expensive technology to improve upon the resulting image captured. The less noise can also be contributed by the of sensor processor DIGiC X.

lostdoggy wrote in post #4274330
Ok hope this will clear it up for you.

The Title of this thread is "...CMOS is less noisy because it consumes less power..." so if this is true then CMOS in cell phone should be less noisy, But it is not.

nevermind, the logic was flawed and that example didn't really apply since cell phone cmos sensors are on a whole different playing field than DSLR sensors, but whatever.

::: connor

lostdoggy wrote in post #4274330
Ok hope this will clear it up for you.

The Title of this thread is "...CMOS is less noisy because it consumes less power..." so if this is true then CMOS in cell phone should be less noisy, But it is not. Now if you continue to read on to later posts I speculate that because Canon incorporated intergated AD convertors and Amps into the CMOS sensor they were able to use a less expensive technology to improve upon the resulting image captured. The less noise can also be contributed by the of sensor processor DIGiC X.

Yeah, as I've said a couple of times in this thread I don't know much between CMOS and CCD. Noise has several causes and factors: the inherant noise in the reading process, which is affected by pixel well size, and the various electronic processing the signal goes through -- it all contributes to what is called Read Noise. Some of it is unavoidable and some, such as amplifier noise, might be small but I'm sure that all the sensor design companies are searching for ways to tamp it down.

One othe interesting factor is concerning the efficiency of collecting the photon data. I don't know much about it, but I've read that current technology is capable of up to 50% efficiency, and that's considered good. But, that means that half or more of the useable photons are lost, which means if more can be collected that means more good photons and less proportionate bad ones. I've read that Canon has really worked on the 1Ds Mk III efficiencies to make those 21MPs work well, but I haven't seen any specifics.

One reason why CCDs are found in compacts, is that they can be turned "on or off" rapidly, thus eliminating a mechanical shutter. If it had a CMOS, it would need an actual mechanical shutter to control the light reaching the sensor. This is why the 1D classic and some of the other Nikons can reach a 1/500s shutter spead, because they have CCD, so you can control the length of time the CCD is capturing light, and not only limited to the shutter speed.

You should also track down and read Canon's white paper on CMOS and full frame sensors. It's full of good info.

Both CMOS and CCD imaging sensors have come a long, long way in the past 15 - 20 years.

Probably CCD is currently cheaper to produce, because only a couple companies do it and there are volume savings. (Nikon does not produce their own, CCD or CMOS... currently they buy them from Sony, one of the major producers.)

Crosstalk between photosites certainly is a key contributor to image noise, especially at higher ISO.

There are several factors regarding crosstalk. One is the size of the photosites, or how crowded the sensor is. Another is heat, which is a by-product of the amount of power needed to activate the sensor. CCD need more power than CMOS, so tend to run hotter.

The length of the exposure also can be a contributing factor, as heat builds and causes more crosstalk. Thus the need for more aggressive noise reduction on longer exposures.

So, we might expect larger CMOS to be "quieter" than smaller and more crowded CMOS chips, assuming equal resolution. We might also expect the best image quality to come from shorter exposures. And, as a general rule, CMOS should be "cleaner" than CCD. As a rule, small chips of either type should have more trouble producing clean high ISO images, and really small chips may be restricted in terms of ISO and in length of exposure.

All this is pretty well born out by reality.

But there are a couple wild cards in all this. One is other related hardware that's used to process images "downstream" from the sensor. The other is the software that's used. These also contribute to whether or not an image is clean with relatively little noise. So, manufacturers have been able to push CCD to much better quality than might have been thought possible years ago. CMOS also have been improved considerably.

Yes, other manufacturers are beginning to follow Canon's considerable lead with CMOS. Canon committed to setting up their own manufacturing some years ago, and has been reaping the rewards of that decision early on.

Olympus was among the first to switch to CMOS.the very small size of the FourThirds sensors pretty much demanded it if they hoped to keep close in the megapixel race.

In addition to the D3, the Nikon D300 with it's 12MP+ sensor in 1.5X/APS-C probably needs CMOS even more (and is getting it).

The Sony A700 will be using essentially the same sensor as the D300. After all, Sony is making those CMOS for themselves and Nikon.

Some recent things to watch include that Canon has reportedly developed CMOS that are more usable in compact digital cameras. If resolution and performance in those cameras is to improve much more, it will probably need to be with CMOS sensors.

Canon has also developed a larger CMOS with 50MP resolution! It's expected to mostly see industrial use initially. But, hey, who knows!

Sony has developed a new "one pass" CMOS manufacturing process that's said to reduce cost significantly.