Understanding Sensor Size

When shooting in our nation’s national parks, you can get all sorts of questions from inquisitive visitors. Often times these questions are something along the lines of, “Is that lens heavy?” “Is all that equipment expensive?” or “Can you see Pluto with that thing?” The answers to these questions are, yes, definitely yes, and no.

But there are other questions you might get from curious park guests that can immediately inform you of the person’s involvement in photography. These questions are often times a bit more specific. The mark of a seasoned photographer is often displayed in what questions they ask about your equipment. The most common of which is, “Is that a full frame or crop body?” Short of having an entire company’s camera body lineup memorized, the best way to tell is simply to ask. So, why does it matter? Well, there’s a lot you can tell about a photographer and what they are shooting by knowing about their sensor size. Let’s take a look.

What is a sensor?
As I’ve touched on briefly in previous posts, the most important component to your camera is the sensor. Without it, you can’t take photos. At least, not digitally. Before digital photography became the behemoth it is, the days of film ruled, and the concept of varying sensor size was foreign to all but the most dedicated camera spec nerds. Nearly everyone shot 35mm film (at the time referred to as “small format”), and a few folks shot medium format or large format film, but that was about it. 35mm has now become the standard in photography and as such, digital camera companies have relied on that as a benchmark with which to format their sensors. Nowadays, the camera sensor is the key component in capturing an image, rather than film. These sensors work by interpreting light particles as data points and formatting an image of variously colored pixels and sending those signals to a computer responsible for recomposing those pixels in the same position they were triggered, reproducing a digital image. There’s loads of science and technology behind this concept and entire textbooks have been written about it, but for now, that’s the bulk of it.

Here you can see the size comparison between various sensor sizes. Credit: Wikimedia Commons.

Why are there different sized sensors?
The sensor in your camera is capable of incredibly precise measurements, and as such, can be incredibly difficult (and expensive) to mass produce. As a result, camera companies have determined that by shrinking the overall space upon which your sensor will read and reproduce an image, they can also shrink the overall cost of that same sensor, as well as shrinking other components of the entire camera, such as the body and lenses necessary to achieve common focal lengths. These different sensor sizes have for the most part fallen into three main categories. Full frame (using the full 35mm equivalent), crop sensor (a cropped version of the same 35mm equivalent), and four thirds or micro four thirds (which use an even smaller sensor with a 4:3 ratio instead of the more common 3:2 aspect ratio, hence the name). There are pros and cons to each, and depending on the style of photography you enjoy, and your budget, you may find yourself looking at entirely different cameras than you did before. There are also about a dozen other sensor size formats, but we’ll focus on these three as they have become the most common offerings among the major manufacturers.

One of the most popular full frame cameras on the market, the Canon 5D Mark IV

Full Frame
Full frame cameras have widely become the “gold standard” of photography and for good reason. These cameras have a 35mm sensor and have for decades been the “professional” option. When the industry shifted from film to digital, camera companies wanted photographers to already understand their lenses and didn’t want to have to start from scratch with new lens development. So they modeled their digital sensors off the 35mm film, and we now have a standard 35mm digital sensor.

Across the board, most lenses are also measured by their 35mm equivalents, as well as aperture and focal length. There’s some complicated mathematics involved in understanding why changing the sensor size would change the aperture value of a camera, so we won’t get into that right now. But know that larger sensors are capable of increased depth of field, increased dynamic range and better low light sensitivity. This is because the larger sensor provides more space for larger pixels. These larger pixels equate to more control of the individual differences between pixels as they relate to the larger individual photosensitive diodes on the sensor. Basically, the bigger the diodes, the better control your sensor has of the individual colors within the image.

Because of the increased clarity and low light sensitivity available with the larger sensor, full-frame cameras are considered the best quality of the three main sensor sizes, but that quality comes at a price. While there are other camera systems that have even larger sensors, and as a result, even better quality, these systems are frequently tens of thousands of dollars more than even the most expensive DLSR bodies and we’ll leave them out of the discussion for the moment.

Full frame cameras are capable of incredible detail and clarity due to the larger space with which the camera is recording light data. As a result, there are more individual data points spread across the same (or similar) number of pixels and can give you truer colors, deeper clarity and wider apertures resulting in more pronounced bokeh.

Photographers using full frame cameras are also granted the luxury of a common language, as most lenses are marketed based on their 35mm focal length equivalent. And by shooting at the 35mm equivalent, full frame bodies are capable of much wider angle photography, making that tiny flower look so much bigger and bolder in your foreground. So why wouldn’t you want a full frame camera? Good question. Let’s see what the other options are before we go singing the praises of all things full frame.

Crop Sensors
Both Nikon and Canon systems provide crop sensor bodies as well as full frame options. These crop sensor bodies (also called APS-C) are much less expensive and can serve a few other purposes. The crop sensor from Nikon uses a 1.4x crop factor, while Canon’s is 1.6x. This means that you will have to multiply your lens’ focal length by either 1.4 or 1.6 to achieve your true focal length. This can be great for telephoto applications, such as wildlife or sports photography, as you’re granted extra “reach” in every lens you buy. The problem here is that when shooting wide angle scenes, you can not turn off the crop factor, so photographers shooting a full frame body will have a wider field of view than your crop body. The 70-200mm lens that you bought for your full frame body will become a 98-280mm lens for you Nikon folks and a whopping 112-320mm lens for the Canon users out there.

An excellent pro-sumer crop body, the Nikon D500
















Other benefits of the crop body are that since there is less total data processing that happens with a crop body, camera manufacturers are able to produce cameras that are typically capable of higher individual frame rates. For example, the Canon 6D Mkii full frame body is capable of shooting at 6.5 frames per second, while the similarly priced and spec’d 7D Mkii crop sensor body is capable of 10 frames per second. This may not be a big selling point for those of you who like to shoot landscapes or portraits, but I know I have captured a number of unique shots at the 10 frames per second of my 7D Mkii that I would not have gotten with a slower body.

The other major benefit of a crop sensor is cost. These sensors are typically much less expensive to produce than a full frame sensor (on average 20 times less), and, while still capable of taking fantastic images, can provide an entryway into professional level photography for photographers on a tight budget. For comparison’s sake, the average cost of a full frame DSLR body is around $3,000 while top-end crop bodies are rarely over $1,500 with some entry level options coming in around $500.

Four-Thirds Sensors
The third major type of sensor you may see in your search for a new camera is Four Thirds. You may see 4/3 or micro 4/3 sensors, and be wondering, what’s the difference? Micro 4/3 is simply a mirrorless 4/3 body. The crop factor and benefits/faults are more or less the same, so we’ll address them as one in this article. 4/3 sensors are roughly half the size of a standard 35mm sensor. These sensors result in a 2x crop factor, meaning that 300mm lens you’re carrying around is actually capable of shooting at a 600mm full frame equivalent.

The extremely popular and very capable micro 4/3 Olympus OM-D EM-1 Mk ii
















The biggest benefit of shooting 4/3 is the size of the equipment. These cameras are substantially smaller and lighter than even the popular mirrorless options from Sony. The lenses are much smaller as well, and as a result, you can find yourself packing more lenses and taking your gear on longer hikes than you would have before.

Another benefit of these systems it seems is that the manufacturers are more willing to play with new technology to build a customer base. As a result, options like 8K photo/video mode, dual pixel shift, and rapid-fire continuous burst mode are becoming standard on the 4/3 systems. These features should not be seen as a sales pitch, as they are truly capable of capturing some really fantastic footage. If I told you Canon or Nikon was working on a full frame body capable of capturing 30 seconds of 20+ megapixel images at 60 frames per second, you’d think I was dreaming. But that technology is already available on multiple 4/3 bodies, and I guarantee those bodies are a fraction of the cost of anything from Canon or Nikon with the same feature. The advancements in camera technology coming from the 4/3 systems are possible in part because of the dramatically lower cost of sensor production, allowing companies like Olympus and Panasonic to put some real time and money into designing exciting and capable features to complement their cameras and a wide variety of lenses.

The downside of the 4/3 systems is, of course, a loss in image quality. While the 4/3 system manufacturers have really been beefing up their image quality, the math just doesn’t line up to allow for the same dynamic range and depth of field seen in a full frame sensor. These smaller sensors also struggle a bit with autofocusing quickly in low light, so before you run out and buy one to shoot those Sandhill Cranes taking off from Bosque del Apache, take that into consideration. While you may be able to capture some incredible footage with 60 frames per second, you might have to throw out more than a couple of them due to lack of focus.

Final Thoughts
The bottom line here is that there are a ton of great options for intermediate to professional level photography from a wide variety of manufacturers. This is means the options for quality camera equipment will only be getting better as companies fight for their spot within the various sensor size markets. Ten years ago, most folks would never dream of shooting mirrorless, and now I’d say half of my guests on our tours are shooting with a mirrorless setup. It’ll be really great to see the improvements in the next ten years as full frame sensors become less expensive to produce, and equipment gets smaller and lighter. As a backpacking and hiking guide, I’m certainly excited to see what sort of developments are coming to the 4/3 system world to improve their dynamic range. Crop sensors will continue to be more and more affordable, while full frame bodies are shifting to mirrorless to compete with the lighter weight equipment made for smaller sensored bodies.

If looking for a new camera/body/system to shoot, go back to the basics. Think of what sort of photography is most important to you. Decide if you’re willing to sacrifice a bit of image quality for packability. If not, figure out if there’s a mirrorless option that is within your budget. Begin with the end in mind, and make the most of the wide variety of options available. As the old adage goes, the best camera is the one you have. If you’re not able to carry all of your equipment, afford all of your equipment, or use all of your equipment, it’s not going to be worth a whole lot at home in the closet. Check out your local camera shop, rent a couple of different types of cameras, or join us on a tour where our friendly guides and guests will be more than happy to show off their own equipment. In time, you’ll find the right fit for you and your needs. And until then, make the most of what you’ve got and learn to use it well. This will do much more for your photography than any new camera will. Happy shooting!

Chris Gheen







Chris grew up exploring the mountains of North Carolina, originally with his family on weekend camping trips and later as a self-taught rock climber and backpacker, leading him ultimately to a degree in Recreation Management from Appalachian State University with a focus in Outdoor Experiential Education. Immediately after graduating, Chris drove west, knowing the mountains and opportunities for adventure were much bigger. Since then, he has worked in a variety of guiding applications, from small leadership non-profits to adolescent wilderness therapy, to commercial hiking and tourism guiding in California, Arizona, Utah, Colorado, Wyoming, and Montana, always with a camera in hand. Chris loves teaching and sharing his passions and experience with others and is sure to provide careful insight and education whenever the opportunity arises. Chris currently resides in Bozeman, Montana where easy access to Yellowstone National Park allows him frequent trips into the park to photograph wildlife and the unique geologic features of the area. When not behind the lens, he spends his time backcountry skiing, ice climbing, and mountain biking, always on the lookout for a new unique perspective to photograph. The mountains have always been a point of inspiration for Chris and he is excited to capture the beauty of the natural world in an effort to share the space he is so privileged to work in with those around him. For a look at some of Chris’ work, visit his website www.chrisgheenphoto.com