PF 074: What You Should Know About Your Camera’s Sensor Size
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.
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 Canon G7x Mark II or the cameras used in some drones.
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.
They need larger files to print large sizes.
When I look at a photo taken on a medium format camera compared to my Nikon D800 or D810, I don't see a big difference in image quality. If I needed to print something on the side of a Las Vegas hotel, then I'd go for the camera with more megapixels to do the job.
Resolution matters when output matters.
When Sensor Size Doesn't Matter
Assuming that I don't have a large output requirement, I can take excellent photos in good light using almost any modern camera. That's because they all look great in well-lit conditions. You know, like daylight. With flash or strobes.
Great quality of light leads to great image quality.
If I could trigger a flash with my iPhone, I could take a photo that would rival many DSLR cameras. I just don't have a hot shoe on my iPhone.
Granted, there are more issues to photography than sensor size. We mentioned light. Lenses certainly matter. It doesn't hurt to have an interesting subject, either.
Yet the sensor size is less of an issue today for, I estimate, 80% of the shots most people take. I'm totally basing that on the 80/20 rule and the amount of photos I see floating around.
If you're shooting concerts, weddings or night time sports, then get the camera with a full frame sensor. You'll use the benefits of its ability to gather more light.
On the other hand, there is a lot of convenience to carrying a smart phone or a smaller camera. The results we see from lighter cameras are very good and they won't break your back lugging gear around with you. Also, you're more likely to take a great shot somewhere if it's not a pain to take the camera with you.