Does Sensor Size Really Matter?

One of the common debates in photography seems to be an unending grousing about sensor size. What's better for a DSLR, a crop sensor or a full frame? Can you take a decent photo with a smart phone? Why does anyone bother with Micro Four Thirds? Is that even a thing anymore?

There are occasions when sensor size matters to your photos. Fortunately for most of us, those occasions are specific, predictable, and quite often the minority of times most people need to take a photo.

When Sensor Size Matters

Larger sensors collect more light than smaller sensors. Ideally, this allows for higher resolution and better photos.

In practice, modern technology really improved the image quality of smaller sensors. If you're taking a photo in good light at a DSLR equivalence of a midrange aperture, such as f/5.6 or f/8, it's quite likely that you wouldn't notice the difference among many different cameras, from smart phones to medium format.

That's not to say we should toss out our larger cameras. They really do excel at some things due to their sensor size.

Bokeh

A larger sensor provides better bokeh – the defocused area behind your subject when shooting with larger apertures. Larger sensors require larger lenses to fill up the sensor with light.

Smaller sensors require wider focal lengths. Those wide angle lenses do a poor job of creating bokeh. If you want to see great bokeh, rack out a 70-200mm lens at f/2.8 on a full frame sensor camera. That provides some serious blur.

If I use my ultra-wide angle Nikon 14-24mm lens, then my bokeh isn't nearly as desirable. Shorter focal length, less bokeh. Smaller sensor size, wider lenses, less bokeh.

Smaller sensors crop in the image compared to larger sensors, so they need greater distance from the subject to replicate the same bokeh.

Granted, your sensor alone doesn't create bokeh. It needs a lens and comparative distance from the subject. Basically, you just can't cram all of that into a smaller sensor and get the same results. It violates the laws of nature.

Low Light Conditions

Remember what I said above? Larger sensors gather more light. Smaller sensor sizes struggle in low light conditions. If they cannot gather enough light to represent the subject, you start to see digital noise.

I would never think of trying to take photos with my old Nikon D200 (crop sensor) camera above ISO 800. It was horrible at that ISO, too. When I switched to a full frame sensor size in the Nikon D700, I wouldn't hesitate to take it up to ISO 1600. In fact, I could get usable images up to ISO 6400, though they needed a lot of help with post processing noise reduction.

My Nikon D800 is a few years old, but it's far advanced with technology compared to the D700. I laugh at ISO 6400 now.

Crop sensor sizes made improvements. The Nikon D7000 can go higher than the same sensor size in my old D800, but it doesn't get close to the quality I had in my full frame cameras.

Smart phone photos in low light are mostly a reminder that you were someplace blurry in the dark.

Even so, I'm finding some very nice results from the 1″ sensor size cameras used in some modern point and shoot cameras, like the or the cameras used in some drones.

Image Resolution

We know that the megapixel wars were mostly a myth about image quality. Yet there are reasons why some photographers shoot with a medium format camera with megapixel resolutions.