CMOS vs CCD

[Zalfa Chamoun]

Hi again,

 

What would you say is the main advantage, in terms of performance, of CMOS over CCD?

 

Power consumption?

Frame rate range?

Light sensitivity?

or?

 

And would you have any numbers to quantify the difference?

 

Thanks again!

 

Zalfa Chamoun

[Michael LaVoie]

The biggest advantage of CMOS would have to be it's rolling shutter artifact that creates lots of distortion when moving the camera or panning. Unless it's a global shutter (full plane)CMOS, that's kind of a dealbreaker for me.

Edited March 23, 2009 by Michael LaVoie

[John Sprung]

Power consumption?

Frame rate range?

Light sensitivity?

 

Pretty much a wash on all three. CMOS and CCD both convert photons to electrons in the same way. It's what they do with the electrons thereafter that differs.

 

CCD has to move the electrons to the edge of the chip and read them out. Cheap ones do that directly at the edge of the image, the better ones have a whole frame worth of covered storage, which lets them read a frame out while the next one is exposing. Processing has to happen on separate chips. Bright lights in the shot can streak if the CCD doesn't have a mechanical shutter, but the ones with a frame store on board can pull down fast enough that that's rarely an issue.

 

CMOS processes the image right where it forms. It's made the same way other electronic chips are made, so it can do much more right on the single chip. How fast they can read out a frame determines whether they'll have a rolling shutter problem or not. Rolling shutter is a kinda weird thing, sometimes it doesn't bite you when you expect it to, sometimes vice versa. But overall, it's way overblown as a problem. Rolling shutter artifacts are few and far between, much less common than interlace artifacts were back in the video days.

 

 

 

 

-- J.S.

[Brian Drysdale]

. Processing has to happen on separate chips. Bright lights in the shot can streak if the CCD doesn't have a mechanical shutter, but the ones with a frame store on board can pull down fast enough that that's rarely an issue.

 

-- J.S.

 

The high end 3 x CCD cameras since the Sony BVW 400 don't streak - at least at the normal day to day lighting levels that you come across (even the sun doesn't streak, although you can get a small star effect).

 

However, the Genesis does have a streak effect.

[Phil Rhodes]

The main advantage of CMOS is that you can manufacture them with more intricate electronics built-in.

 

This allows things like higher frame rates and potentially lower noise, as well as flexibility to do things like window out part of the sensor. It also makes them cheaper and easier to use, which is why cellphone cameras tend to be CMOS.

 

The downside is that the more non-pixel electronics you put on the things, the less room there is for pixels, which tends to lower dynamic range and increase noise.

 

P

[Peter J DeCrescenzo]

... The downside [of CMOS] is that the more non-pixel electronics you put on the things, the less room there is for pixels, which tends to lower dynamic range and increase noise.

 

Hi Phil,

 

Thanks especially for this "heads up". Very interesting.

 

All the best,

 

- Peter

[chrisssteeven]

CMOS consume low camera power than CCD to reduce heat and enhance battery life. CMOS sensors now producing cleaner images than CCDs. CMOS is cheaper so it is used widely in mobile camera. CMOS reduce camera cost to enable quick acceptance and proliferation.