Why don't digital SLR cameras use three sensors like those 3CCD video cameras?

a little backgroud on image sensors - http://www.cambridgeincolour.com/tutoria...


seeing that sensors can only take in one colour into each photosite - and those Foveon sensors place photosites on top of each other - why haven't they placed 3 sensors around a glass prism like Panasonic and Sony do with their 3CCD sensor video cameras?

that would increase the quality and megapixels of dSLR cameras greatly...

Your tutorial doesn't apply to 3 CCD sensors, which require the light to be split via prism system. Because it doesn't explain them, your question is missing a few facts, like the fact that such systems in video cameras are for very small sensors.

As a result, making an SLR camera with such a system increases its cost and complexity. Moreover, your argument that the quality and megapixels would be increased is not supported by history. Minolta tried a prism system SLR called the RD-3000 and it was a dismal failure. Bayer-based sensors did much better and the cameras weren't as thick.

If you look at a 3-CCD camera they have 1) much smaller sensors physically than an SLR and 2) the cameras are physically often much larger than an SLR. So, to get a 3-CCD SLR, you'd be looking at a huge camera to get a prism-based 3-CCD camera.

That's why Nikon, Fujifilm and others are looking at sensors that go beyond Bayer, but will perform better than Foveon sensors.

And that's why a 3-CCD still camera isn't being made, because contrary to what you claim, it isn't really a practical way to increase quality and megapixels for a digital SLR.

I can think of several reasons.

1. Price. Digital camera sensors a a lot bigger and more expensive than video camera sensors. The consumer level video camera has 740x480 resolution. That's 0.3 megapixel. These sensors are quite cheap to put three of in a camera and still have it in reasonable price range. Try to make a camera with 3 x 12 megapixel sensors, and it will probably double the price.

2. Sensitivity. Foveon or not, to get light to three sensors means splitting it in three streams. Whether you split original stream then split one of the sub-streams or split it 3-way -- your sensors (at least one of them) will get to see at most 1/3 of the light. That means 1.5 stops of sensitivity sacrifice... Not good.

3. Quality - The picture quality of the modern Bayer cameras is so good, it's hard to imagine why anyone will be willing to cope with two problems above for a 3 sensor still camera, and by exactly how much will the quality improve. imagine that it won't improve in proportion with the price increase and having to deal with light loss. Also great post processing is available for still images, which is either unavailable or is very expensive and cumbersome for video. So it's important to get the video colors correctly right off the sensor(s), while in photo world it can be corrected later!

LEM.