Is Bigger Better? Sensor Size Examined

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Full-frame and medium-format mirrorless photo gear use has exploded in the past couple of years. Sony, Canon, Nikon, Fujifilm, Hasselblad, and even Panasonic either just launched or will soon have some big-sensor cameras coming out. After years of companies and photographers disagreeing about the merits of APS-C and Four Thirds sensors, it leads us to question of whether bigger really is better.

The Obvious Answer

Yes. All things being equal (remember this phrase, it is the all-important qualifier), the bigger the sensor, the better the quality. Please, refrain from pointing out differences in camera designs and lenses, etc. Looking at the sensors alone and assuming perfectly equal lenses and light quality, the images coming out of a bigger sensor will be better. This is backed up by the science underlying digital imaging technology.

There is a tried-and-true explanation for why bigger sensors are better. At its core is the idea that if you have bigger individual photosites, which I will now refer to as pixels for simplicity’s sake, the information captured will be more accurate. Now, to dramatically oversimplify: Imagine each pixel is a bucket collecting rain. Bigger buckets (in this case bigger refers to the opening, or aperture if you will) will collect more rain and provide a more accurate measurement of average rainfall. A sensor with bigger pixels will collect more light, and more light will generally improve image quality. Easy concept to understand, right?

From an imaging perspective, the easiest way to see the improvement is to examine noise. Larger pixels collect more light data, meaning that any errant information can be averaged out to produce a more accurate final measurement. This also explains why raising the sensitivity and using a higher ISO results in more noise—the sensor is recording less data and is unable to create as accurate an image as you would get at the lowest settings. Assuming the resolution remains the same between formats, the larger sensor will obviously have bigger pixels and, therefore, will deliver better image quality.

Really, this does come down to pixel size instead of actual sensor size, but then you must consider practical matters. Going with a 10MP sensor in APS-C can be more limiting than going with 24MP in a full-frame sensor, even though noise and other performance may be very similar between the two. Dynamic range is a topic that comes up often in favor of larger sensors. This is more related to pixel size than sensor size, although having larger pixels generally results in greater usable dynamic range as you go to higher sensitivities.

Another subject commonly mentioned in this conversation is depth of field. Now, if you take the same lens, say a 50mm f/1.4, and shoot at the same aperture on both full-frame and APS-C sensors and make sure to frame everything the same way, the depth of field will be shallower with the full-frame setup. This, however, can be solved with lenses specifically designed for the format, and an understanding of equivalence. Larger apertures will mean shallow depth of field on the smaller format, to make up for the difference, yet it still won’t be a perfect replacement much of the time.

Full-frame sensor (left) versus APS-C sensor (right)

In summary, bigger sensors will give you better performance, both practically speaking and technically, because images will be cleaner and/or sharper, again, if all things are equal.

Current Events

Looking at the market, it seems that either photographers have begun asking for larger sensors or that manufacturers think this is going to be the next big thing. The biggest news from 2018 is from the big two: Canon and Nikon. Both launched completely new mirrorless systems centered around large mounts and, of course, full-frame image sensors. They also crammed some of their latest tech into these models with features we have yet to see on their flagship DSLR lines. Mirrorless got its advantage from being smaller. At first this also meant smaller sensors, but now manufacturers are proving that they can make full-frame models notably lighter and smaller, as well.

The Canon EOS R is a lighter and more compact take on its full-frame DSLRs, definitely shaving some weight and bulk, thanks to the new mount. It introduces a touch function bar on the back for expanded controls, but sits solidly in the middle of the company’s lineup. We are expecting them to go both high-end and entry-level with future releases, but one thing we can see now is a focus on outstanding and unique glass. A major release is the RF 28-70mm f/2L USM, the first f/2 constant aperture on a full-frame mid-range zoom.

Canon EOS R Mirrorless Digital Camera

The Nikon Z Series is a huge shift for this manufacturer, basically delivering mirrorless equivalents to its hugely popular full-frame DSLRs. Think of the Z7 as a D850 and the Z6 as a D750. They are focusing on the doors being opened by using a larger mount. They even add UHD 4K with N-Log and 10-bit output, a first for Nikon cameras. Ultra-fast lenses and high-quality compact primes are the focus, and the Noct 58mm f/.095 is going be a highlight going forward.

Nikon Z7 Mirrorless Digital Camera

In terms of actual big sensors, Fujifilm is making medium format more accessible to us regular folk with the GFX 50R, a rangefinder-styled 50MP mirrorless that comes at the best price we have ever seen for anything like it. The ever-expanding GFX system looks great, with many new lenses coming down the pipe. Sony took a small break, but its sole release of the a7 III changed what we consider “the basic model.” It has seriously pro specs, a brand-new sensor, and with Sony’s history as the first major proponent of full-frame mirrorless, it has years of development and lenses behind it.

FUJIFILM GFX 50R Medium Format Mirrorless Camera

Finally, the most intriguing piece of full-frame mirrorless news comes from Panasonic, Leica, and Sigma. The three companies announced the L-Mount Alliance, a new group dedicated to creating cameras and lenses with Leica’s L mount. Panasonic is striking hard with the S1R and S1, two full-frame models that promise some impressive specs. What we don’t know is what will be coming from the other two in the group, but Leica’s SL is still a solid piece of tech, and Sigma has a stellar reputation from its Global Vision lenses. We should see more early next year.

While simple, this should tackle many of the basic benefits of larger image sensors. Do you have anything you want to add to the conversation, or do you want to make a case for your camera system? Join us in the Comments section, below, for a discussion.

14 Comments

The dog in both shots is identical so how can it be two different cameras?

Maybe it is a cardboard cutout of a dog? 

Dennis A Livesey wrote:

The dog in both shots is identical so how can it be two different cameras?

The backgrounds behind dogs are different. Left background is more blurred than right one. It is called "depth of field". The more blurred background you have the nicer picture looks like. Non-proffesional pictures usually have sharp backgrounds.

The article states that Canon's EOS R "is a lighter and more compact take on its full-frame DSLRs." Compared to a 6D Mark II, it's definitely more compact, but only one ounce lighter. Why so little difference?

The pixel size of the Fuji is more than 150% larger than the pixel size of a Nikon Z7.  But a Nikon Z7 has to be enlarged  ~120% more than the Fuji to attain the same size enlarged image.  So, if the claims of manufacturers are completely true and the quality of the sensor electronics are equal, the Nikon Z7 is the better deal by far...so it seems. (pixel density is exponential (Sensor size over square area), enlargement is merely a linear function).

While I'll totally buy the science of "bigger is better" in this case, I'd rather continue to concentrate of doing the best gig you can do with the tools you have.  Especially with the new sensor/camera technology in the last two or three years.  

I come from the audio world.  I remember folks arguing that they "needed 96K" before they could cut a pro record.  Well, that argument has long been put to rest.  It isn't true.  While I'd rather work with boutique mic preamps like USA built A-Designs and German converters like RME, I can still make a great sounding record with less expensive gear like a UA Apollo and recording at 48K- on either!

I believe sensors in the newest cameras have come of age- or at least are coming of age at this moment in time.  I'm saying that the argument for bigger/better quality is becoming less of an issue in today's cameras.  NO DOUBT, the bigger and better the quality of the camera sensor increase your chances of making great photographs.  But if you can't take a pro photo with a camera like the Sony a6500, you shouldn't be in this discussion.  

The photo presented of the dog with the stream log pool in the background was a terrible choice if you wanted to make full frame look good. I showed the images to a dozen people on my computer screen. NOT one selected the FX over DX. Depth of field often is taken to mean better photos. Reminds me of a Peach Pit press tutorial showing kids in an African Village where ONLY one person’s eyes were in focus, and the rest of the scene was blurred out. I have showed that image to hundreds of people. Without prejudicial discussion. Few thought the scene was captured well. I have owned over $250,000 in camera gear. Large and medium format were my thing for years. But I majored in images that had big depth of field. I belonged to a group known as f64. But depth of field with tilts and swings, etc., is a whole different thing than shallow depth of field photos. I have used in the last fifteen years mostly DX cameras like the Nikon D500. My grandson Christjen has D500 video that is amazing. I want gear that does both stills and video. And facilitates Rapid changing between still and video. I use the Nikon D7500 for that frequently. The heavy descent into full frame is going to mostly push most people taking pictures into becoming Cell Phone Snappers. I plan on buying a Nikon Z6 and 24-70 S lens with the FTZ. And wonder if the Nikon D500;wouldn’t be better for my field camera use. 

"This also explains why raising the sensitivity and using a higher ISO results in more noise—the sensor is recording less data and is unable to create as accurate an image as you would get at the lowest settings"  Thinks about what you're writing.  Can you "raise" (increase) the sensitivity of a sensor?  No you cannot.  A higher ISO tells you the sensor cannot get the optimum amount of light needed for a noise-free image.  Changing ISO does raise sensitivity, it only tells the camera the sensor will NOT be fully sensitized, so digital gain must be applied to the data.  Further, ISO allows one to equalize all cameras at the same exposure--that's its real purpose.  What you may have meant to write is "This also explains why raising the sensitivity of your sensor you can use a higher ISO with LESS noise--the sensor is recording more data and is able to create a more accurate image than you would get with a smaller sensor at the SAME ISO.    

Max R. Is right!

Is Pentax done? There is no mention of them in your article. Last time I checked they had the full frame K-1 and K-2 models available.

Hi Wayne,

Pentax is far from done. They have the K-1 Mark II full-frame DSLR, the GR III on the way, and a highly-successful Theta line. However, this article is focusing on full-frame and medium-format mirrorless development, and Pentax does not currently offer one of those.

This article is focusing on full frame and medium format development! You got that right! And the case for DX, now even avoided by Nikon who makes over 1/2 of its money on DX DSLR Cameras to date, see the latest sales data worldwide, not just in Japan. The heavy propaganda towards Full frame is certainly full tilt. Now I would say, look at the reduction of higher level cameras compared to cell phone. Manufactures proceed at your own risk!

"...this article is focusing on full-frame and medium-format mirrorless development..."

No mention of Hasselblad X1D?

Hi Brandon,
Not this time, as this was referring to "Current Events," meaning everything from 2018. The X1D was released in 2017. Still a solid camera.

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