how do camera lenses have a “resolution” and a mega pixel count?

Question

I get details can be blurry on a bad lens but how is this like pixel resolution?

CCTV lenses are often 1-5 megapixel lenses. How can a lens have a mega pixel count?

What does it mean for a lens to “resolve” more detail? Is this just about sharpness?

Also when buying DSLR lenses how can you tell what their resolution will be?

Thanks 🙂

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Answer 1

It’s not the lens. It’s the sensor in the camera body. It’s a grid of light-sensitive semiconductors. The more of these, the higher the number of pixels.

These are kind of expensive to make in any decent size since one bad sensor ruins the whole thing. These are made on wafers, so if you put hundreds of tiny ones on a wafer and two bits are bad in the area of two sensors, you only lost a couple out of hundreds. But if you make big ones, maybe ten per wafer, you lost ten percent of your wafer with the same two errors.

But we want more megapixels! so we pack more sensors in the same area of a small chip. The problem is, smaller, tightly-packed sensors are more susceptible to noise and don’t gather as much light. So small sensors with high megapixels will generally have lower quality.

Or we make a really big chip with ten times the surface area, and we put the same number of sensors on it, but much bigger ones. These have lower noise and gather more light, so the image quality is much improved.

So let’s say you’re looking at a 24 MP DSLR with an image sensor of 2/3″. Don’t expect quality, but you won’t pay much. Up the chain a bit you may find the same 24 MP with an APS-C sensor, which has over six times the imaging area, and photos will probably be a lot better. Go higher to full frame and you’ll pay a lot more money, but you’re getting about 15 times the imaging area of the first camera. Each sensor is about 15 times as big, so much lower noise, much better light gathering ability.