Education

Full Frame vs. Crop Sensor Cameras

The current camera market has a massive variety of bodies and formats to choose from. If
you’re just starting out on this journey, the selection can be a little bit overwhelming. One of the
most frequent questions I get asked is, “Should I buy a full frame or a crop camera?” and
“What’s the difference?” The below images were taken with a crop and FF camera with
comparable focal lengths and settings, so my first question is, “Which one is which?”
I like to ask this question to feel out what they are really looking for in their images and what
they want to do with the final result (printing, vs social media posting). Cameras have come
such a long way that lines between these two sensor sizes is really starting to blur. If the images
above look pretty equal in their eyes, then I can dig into cost as a factor vs weight and so on.
But before we get ahead of ourselves, let’s talk about what a full frame and a “crop” frame
sensor is. Oh, and I’ll answer which is which in a bit.

Full Frame Camera

Simply put, a full frame camera has a sensor size on par with the size of a 35mm film negative;
roughly 24mm x 36mm. Full frame cameras are designed to capture the same amount of light
across the sensor as 35mm film cameras, given the same lens. Originally aimed at the working
pro, more complex and customizable technology and functionality tends to go into these bodies
which usually results in a meatier price tag. That’s why they are often referred to as “pro bodies”
in the industry. But take that label with a grain of salt as there are many professionals using crop
sensors as well these days.

Crop Sensor Camera

Crop sensors have a smaller physical size than a full frame sensor; meaning less light is
gathered across the sensor, given the same lens. For example, if you were looking out your
window with no obstructions, there would be a certain amount of light entering the room, and
you would have a specific view of your scene. Now, standing from the same spot, if you covered
10% of the edges of the window, there would be less light in the room, and you would have a
“cropped view” of your scene (you’d no longer see what was at the edges of the window). While
the full frame cameras have a 24mm x 36mm footprint, crops cut away the edges to leave you
various sizes based on the manufacturer. For example:

  • APS-H (Canon) uses 19mm x 28.7mm
  • APS-C (Canon) uses 14.8mm x 22.2 mm
  • APS-C (Sony, Nikon, Fuji, etc.) uses 15.7mm x 23.6mm
  • Micro Four Thirds (Olympus, Panasonic) uses 13mm x 17.3mm
  • 1” Sensors (Nikon, Sony) uses 8.8mm x 13.2mm

There are many other examples of sensors out there, but these are some of the main ones you
probably have heard of.

It used to be true that crop bodies were not as feature rich as their full frame cousins, but as this
market grows, “pro” features and tools have made their way into here as well.

Lenses

So this is where lenses come into play. Many companies, like Nikon, make a range of lenses for
their full frame “pro” bodies which they call the FX line as well as a line for their crop bodies
called the DX line. The FX and DX lenses are designed specifically for the sensors that will be
using them, and like FX bodies, the FX lenses carry a more steep price tag but also a higher,
more precise build. A DX lens is optimized for the DX sensor, while the FX lens is optimized for the FX sensor by casting the appropriate size circle of light onto the sensor. If a DX lens was
placed on an FX body (which you can do), the circle of light would be smaller than the sensor,
causing a strong vignette unless you crop to DX sized image – essentially a zoom. I’ll explain
that a bit more.

If I were to take a 50mm lens off a full frame camera and stick it on a crop sensor body, it’d still
render like a 50mm lens (larger circle of light than the sensor can handle), but it’d only be
grabbing light from the center portion of the lens – in effect performing a digital crop of the center of the image. To make it a little more clear, take the image below. This was taken with a proper full frame 50mm lens on a full frame body. If this same lens was put on a 1.5x crop sensor, only the middle portion (shown below in red) would be captured. Contrary to belief, this does not affect the depth of field, you’re simply grabbing the relative center of the image, chopping off all the edges. The rest of the light along the edges has no sensor to hit and therefore isn’t captured.

 

This is where manufacturers compensate by making 35mm (full frame) equivalent lenses which
tend to be smaller or lighter in weight. To get the same field of view as a 50mm lens, for
example, a 1.5x crop lens manufacturer would use a wider 32mm lens. Now, standing in the
same spot, a 50mm lens on a full frame body and a 32mm on a 1.5x crop body, you could take
a very similar image. And that’s precisely what I did for the images near the top of this article.
Below are the files (I color graded the example at the top of the page to closely match the look
and feel, so below are the raws) from the full frame Sony A7R II with the Zeiss Loxia 50mm (left) and the Fuji X-T2 with the Zeiss Touit 32mm lens (right).

Two different length lenses on their respective bodies, taken from the same tripod spot,
resulting in the same edge to edge view. Though I kept the ISO the same, notice the shutter
speed and depth of field was corrected in camera match the scene with the two focal lengths.
Without geeking out too much, a full frame 50mm lens at f/2.8 has close to the same hyperfocal
distance as a crop 32mm lens at f/1.8. By definition, the distance between a camera lens and
the closest object that is in focus at infinity is the hyperfocal distance. The “blur” is what occurs
on either side of this plane. By adjusting the f-stop (and consequently, the shutter speed to have
the same exposure) on one camera, you can get a very similar image and depth of field. For my
testing, I carried around a hyperfocal calculator app so that my images would always be similar.

Pixel Density

This is another area I’ll only touch on, but for the sake of discussion, this is the number of pixels
used to capture the same image for a given lens. The crop body I used here was the Fuji X-T2
which has 24MP, and the full frame body was the Sony A7R II with 42MP. There is 2.25 times
more space on the full frame sensor, meaning, if it were packed as tightly as the crop, there
would be 24MPx2.25 (1.5×1.5 crop factor) = 54MP pixels. But at just 42MP on the Sony, it is not as densely packed, allowing for larger light gathering pixels, and therefore, more light falls onto each one. Consequently, this results in less noise at higher ISO’s (each pixel captures more
light) on the full frame. So, based on the MP count you’re looking at there are potential
trade-offs.

Look at the raw results again. I focused on the message board of the scene above. Taking out
lens factors, below are 100% crops of the crop (left) and the full frame (right):

Depending on your use of the images, the ability to render details like this may or may not be a
factor. Below is one more detail (100% crop) so show micro-contrast and sharpness when
zoomed.


Conclusions

Both full frame and crop sensors have advantages and disadvantages that matter to the
photographer; cost vs image quality usually being a huge factor and where most of the trade
offs happen. Following an understanding of lens lengths and how they are paired with the
sensors, I hopefully shed a little light on the crop vs full frame story. It comes down to what
produces the images you want best and what body you want to have by your side. I know
several pros using crops not only as a backup, but as a main shooter as well as hobbyists that
only swear by full frame bodies. Both sets are producing equally stunning images.

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