Is there a difference in the sensor technology in entry level cameras vs. that in pro or semi-pro DSLRs?

Question

Obviously there are differences in everything, both optics-wise and mechanism-wise, but I would like to know:

1. Are the materials used to construct sensors (disregarding sensor size) different at any level ranging from entry-level to professional-level cameras?

2. What is the impact of sensor size: do larger sensor sizes result in higher-quality images?

3. Are image differences due mainly to optics or sensors? I've noticed that pro cameras produce very vibrant colors and very sharp images: does the lens or the sensor have a greater impact?

4. With high-quality lenses, can entry-level and professional DSLRs produce equivalent pictures? Or is a professional body required for the best images?

Answer

It depends where you draw the line. Many "pro" level cameras use full-frame sensors, which are about twice as big in area as the APS-C sensors common in lower (including mid-range) dSLRs. This gives an advantage, because surface area is the best way to get more light, and more light is never bad. So, more expensive cameras will have an image quality advantage there. (With the corresponding tradeoff in size and cost as well.)

But, the basic technology is the same. These days, sensors are usually CMOS — the other leading option is CCD. These have various trade-offs, but both can produce great images.

Even when you get down to point & shoot cameras, we're still really in the same ballpark — CMOS and CCD, almost all using the same Bayer pixel layout. The main difference is that those cameras use very small sensors, so the technology is focused on enabling that. Pixel density is higher (which is generally bad). There are some sensor tricks like backlit CMOS which only show up in these small sensors — probably because the quality gain isn't worth the cost on a larger scale. As those technologies mature, they may be available on bigger sensors too — or maybe not.

The vibrant, sharp colors you've seen from pro cameras are probably mostly because someone put a lot of time into making those images look good (both in the field and in post-production.)

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