Resolution vs. Sensor Size: Which Matters More?

David Pogue
·Tech Critic
Updated
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Mr. Pogue: 

Your articles and reviews have definitely caught my attention about what Sony is doing with large sensors in its cameras — so much so that I have narrowed down the choice for my next purchase to Sony’s top-end point-and-shoot, the RX-100 (forgoing the higher price and slight feature upgrade of the RX-100 II) and the entry-level interchangeable-lens NEX-3N.

But in comparing them, I ran up against a mystery that even my much more knowledgeable professional photographer girlfriend couldn’t figure out.

Specifically, the NEX-3N’s sensor is four times the size of the RX-100’s (about twice as long in each dimension) — but the maximum resolution is higher for the RX-100: 5472 × 3648 vs. 4912 × 3264 for the NEX-3N.

If the differences in sensor size and resolution were small, I’d ignore it. But how a sensor four times as large, and apparently of the same type, can produce photos of lower resolution seems inexplicable. After all, what’s the point of stuffing a larger and presumably more expensive sensor into a camera if not to achieve higher-resolution pictures?   

Any ideas? Or, put another way, what am I missing here?

I love what you’re doing with Yahoo Tech. Keep up the good work.  

—Bob Woolley

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Hi, Bob!

Oooh! I know this one!

I’m afraid to say that you’ve fallen victim to the Big Old Camera Lie, that more megapixels = better photos. It’s absolutely untrue.

You’re right that the NEX camera’s sensor is much bigger than the RX-100’s.

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You’re also right that the larger NEX has  lower resolution than the RX-100: 16 megapixels instead of 20.

The solution to the mystery is staring us in the math: The NEX camera has bigger pixels than the RX-100! (Here I’m referring to pixel sensors, technically known as photosites.)

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Both cameras are extraordinary — but really, my lifelong campaign to emphasize the importance of a big sensor is just a simplification. What you really want are big pixels.

Bigger photosites soak in more light and generate less heat, which means less digital “noise.” Other things being equal, you always want bigger pixels on your sensor.

Both of these cameras have  way more than enough megapixels. You could print billboards of these pictures. That being said, the NEX is the more desirable camera, because its individual pixel sensors are so much bigger.

Hope this helps!

—DP

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