When choosing your first camera, you’ve probably come across the terms “full-frame” and “APS-C” many times. Or perhaps you’re wondering if it’s really worth changing from an APS-C camera to a full-frame one. What’s the difference between the two, and how does it matter? Read on to find out.

1. APS-C and full-frame: 2 different-sized image sensors
2. Consideration #1: Impact on camera and lens sizes
3. Consideration #2: Low light and high ISO performance
4. Consideration #3: 1.6x crop factor
5. Consideration #4: Depth of field
6. In conclusion: APS-C or full-frame camera?

 

APS-C and full-frame: 2 different-sized image sensors

On a digital camera, the image sensor is the part of the camera that receives light entering from the lens and converts them into electrical signals that can be viewed, analysed, or stored. They come in different shapes and sizes, but there are certain standard formats that are widely used by camera manufacturers.

Whether you are buying a DSLR or a mirrorless camera, the two formats that you will most commonly encounter are “full-frame” and “APS-C”. While there may be very slight variations between different camera models, generally, the image sensor dimensions are as follows:
Full-frame: 36 x 24mm
APS-C (Canon): 22.3 x 14.8mm

35mm full-frame

“Full-frame” is also known as “35mm full-frame”, and it originates from the 35mm film is used in film cameras. If you measure a 35mm film negative, you will find that the image area is 36 x 24mm—which happens to be the around same size as the image sensor on a full-frame camera.

Incidentally, 35mm film itself was adapted from the 35mm film reels used in cinema. Read about the history and learn about cinema cameras in:
6 Things About Cinema Cameras that Serious Video Creators Should Know

APS-C format

“APS-C” stands for “Advanced Photo System type-C”. It originates from the C (“Classic”) format of the APS film negative format that was first introduced by manufacturers in 1996 as part of an effort to make cameras more accessible to non-professional camera users. When digital photography became more popular, camera manufacturers incorporated digital image sensors that were around the same size.

 

Consideration #1: Impact on camera and lens sizes

When you remove the lenses on some mirrorless cameras, you can immediately see the image sensor, and the size difference is quite obvious when you put a full-frame and APS-C mirrorless camera side by side. On DSLR cameras, the image sensor is behind the mirror but the same applies.

Camera size

The most immediate impact of the sensor size is on the size of the camera. After all, the camera must be big enough to house the sensor and everything else! On DSLR cameras, it also affects the size of the mirror that’s right in front of the sensor and the pentaprism or penta-mirror at the top, which in turn further adds to the size and the weight. That’s why there is a limit to how light and compact a full-frame camera can be, compared to one with an APS-C image sensor.

Back row: DSLR cameras EOS 6D Mark II (full-frame) and EOS 200D II (APS-C), 
Front row: Mirrorless cameras EOS R6 (full-frame) and EOS M50 Mark II (APS-C)
APS-C cameras can be made smaller and lighter than full-frame cameras.

Lens size

The image projected by a lens is a circle. A full-frame image sensor requires a larger image circle than an APS-C image sensor, which means that the glass elements inside the lens need to be bigger to cover the full sensor area. In comparison, the much smaller image circle required by an APS-C image sensor allows lenses for APS-C cameras to be smaller and lighter.

How it affects your choice

The image sensor size influences the size and weight of the camera and lens bodies, and also impacts the cost of producing them. If you need something small and light, and/or are on a smaller budget, you’ll probably find yourself looking at more APS-C camera models.

 

Consideration #2: Low light and high ISO performance

The image sensor size also affects the possible pixel size, which in turn can affect the camera’s low light performance.

Here’s a simplified illustration of what the same number of pixels might look like on an APS-C and full-frame image sensor. Notice how the larger area on the full-frame sensor allows pixels to be larger?

The pixels on an image sensor are photosites that collect light, which is in turn converted into data. This data is used not just for forming the image, but also for processes such as light and exposure metering, or Dual Pixel CMOS AF calculation*. Under the same light conditions, a larger photosite area technically allows more light to be collected. This increases light sensitivity and reduces the signal-noise ratio, which contributes to less image noise at high ISO speeds as well as better overall low light AF performance*.

* On mirrorless cameras, and on DSLR cameras during Live View shooting. DSLR cameras have a separate AF sensor for OVF shooting.

What about full-frame sensors with more megapixels?

In reality, a lot of other factors influence low-light performance:

- Smaller pixels mean finer resolution, and this also means that the grains of any noise produced appear finer and less obvious

- The image sensor structure: Conventional image sensors have circuitry around each pixel, which takes up space on the sensor and affects the actual pixel size. The circuitry and actual pixel size depends on the camera model. However, a stacked sensor structure like the one on the EOS R3 moves the circuitry behind the pixels, leaving more room for larger photosites.

- Technological advancements: Things like noise reduction technologies and pixel efficiency are always improving.

In that sense, besides just the size of the image sensor, you will also want to consider the other technologies involved. A newer, high-end APS-C camera might have low light performance that is just as good or better than a lower-end full-frame camera released years earlier.

EOS RP (full-frame) @ 35mm, f/4, 1/60 sec, ISO 12800

EOS M6 Mark II (APS-C) @ 13mm, f/11, 1/15 sec, ISO 12800

 

Consideration #3: 1.6x crop factor

APS-C image sensors are also called “crop sensors”. Can you guess why?

Let’s see what happens when we shoot an image from the same spot, using the same focal length but with different camera sensor sizes.

Notice that the angle of view captured by the APS-C sensor is narrower? In fact, the results are the same as what you would achieve shooting with a 1.6x longer focal length on the full-frame camera. For example, if you used a 50mm lens on an APS-C camera, the resulting images would have the same angle of view as those shot at 80mm (50 x 1.6) on a full-frame camera. This effect is called the “APS-C crop”, and 1.6x is the “crop factor”.

In this article, we shall call the focal length that corresponds to the angle of view after the APS-C crop the “equivalent focal length”.

When does it matter?

The angle of view also depends on your distance from the subject, so with most everyday subjects, you won’t really feel much of a difference. However, it does make a difference if you like getting closeups of your subject, and if you like to shoot ultra-wide-angle images.

APS-C: It’s like perpetually having a longer lens

With the crop factor, it’s almost like you automatically have a longer lens. A 100mm lens works like a 160mm lens, 200mm lens works like a 320mm lens and a 400mm lens works like a 640mm lens—perfect for subjects like animals and wildlife, where it always helps to have more reach.

EOS M50 (APS-C camera) + EF‑M55‑200mm f/4.5‑6.3 IS STM @ 187mm (299.2mm equivalent)

You never know when having more reach will come in handy—it certainly did for photographing this lotus flower close up from an appealing angle, all the way from the other end of a pond! The APS-C camera and telephoto zoom lens combination used here weighs a very hiking-friendly 647g, much less than any existing equivalent full-frame lens and camera combination.

How about the 1.6x crop mode on some full-frame cameras?

Some full-frame cameras have a 1.6x crop mode, which allows you to view and capture scenes with the APS-C crop effect. That’s very useful as you can check the composition with the close-up effect on the spot without having to use a longer lens.

However, as only part of the image sensor is used to record the 1.6x crop image, the resulting image is less than the full resolution of your camera. For example, for the images below, using the 1.6x crop mode on the 30.3-megapixel EOS R resulted in a 4176 x 2784 image—about 11.6 megapixels.

It probably won’t matter much if you are going to just share the images online without much editing. But if you intend to crop your images even further during post-processing, having fewer megapixels will limit how much you can crop. It could also affect the quality if you are making a large-size print.

2000px crop from an image shot in 1.6x crop mode
Original image shot at 200mm on the EOS R (full-frame) + EF70-200mm f/4L IS II USM

Images generally have to be at least 2000 pixels on the longest end for best results when viewed across most display devices. The image above was shot in 1.6x crop mode on the EOS R, and taking a 2000 pixel crop from it (bottom image) gave the results at the top. Cropping further could cause the image quality to look less sharp and more pixelated especially on bigger screens.

On a 24-megapixel APS-C sensor camera like the EOS M50, you would get a larger original image (6000 x 4000 pixels), where a 2000 pixel crop would allow the bird to fill more of the frame. The other costlier options would be to get a longer lens, or use a full-frame camera with more megapixels.

 

FAQ: Can I use my APS-C lenses on a full-frame camera?

Lenses designed for APS-C DSLR cameras (EF-S and EF-M mount lenses) won’t fit on a full-frame Canon DSLR camera. Even if you manage to attach them, the smaller image circle is likely to cause vignetting on a full-frame sensor image. The full-frame EOS R system mirrorless cameras can take RF-S lenses directly, and EF-S lenses via the EF-EOS R mount adapter. However, you automatically get switched to the 1.6x crop mode where only part of the image sensor is used. To maximise a full-frame camera’s capabilities, you will have to use lenses that are designed for full-frame cameras.

 

Full-frame cameras: take full advantage of ultra-wide-angle lenses

Shot at 14mm on the EOS R5 (full-frame) + RF14-35mm f/4L IS USM

If you plan on taking lots of wide-angle shots, you might want to consider the lens choices available as the APS-C crop automatically makes the angle of view narrower than on a full-frame camera. For example, mounting a 16mm lens on your APS-C camera gives you an angle of view like that shot at 25.6mm (16 x 1.6) on a full-frame camera (“25.6mm equivalent”).

This isn’t so much of an issue if you use the ultra-wide-angle zoom lenses designed specifically for APS-C cameras, such as:
- EF-M11-22mm f/4-5.6 IS STM (for EOS M series cameras)
- EF-S10-18mm f/4.5-5.6 IS STM
- EF-S10-22mm f/3.5-4.5 USM

These offer a focal length range that go as wide as 16mm equivalent (for the EF-S lenses) or 17.6mm equivalent (for the EF-M lens), and can give surprisingly good results. However, due to the technical challenges of designing ultra-wide-angle lenses with minimal distortion, if you want to go even wider, you’ll have more options with a full-frame camera.

Learn more about what you can do with wide angle lenses in:
Lens Basics #6: Wide-angle Lenses
Exploring Wide Angle Lenses Part 1: Photo Effects of Wide-Angle Lenses

More fun facts about lenses in:
Lens FAQ: What Does a Lens Name Mean and Why are Some Lenses White?

Know this: The circular fisheye effect is achievable only on a full-frame camera

Love playing around with different lenses? If you ever get your hands on the unique EF8-15mm f/4L Fisheye USM fisheye lens, a full-frame camera lets you achieve something unique with it not possible on an APS-C camera:

EOS R + EF8-15mm f/4L Fisheye USM @ 8mm

This is called the circular fisheye effect, and it provides a 180-degree view of the scene. It’s only possible on a full-frame camera. The crop effect of an APS-C camera would crop the image so that it’s no longer a full circle.

Diagonal fisheye: Possible on full-frame and APS-C

EOS R + EF8-15mm f/4L Fisheye USM @ 15mm

Regardless of whether you use an APS-C or full-frame camera, you still can get a dynamic effect with the diagonal fisheye effect, which appears from around 12mm full-frame equivalent on a fisheye lens.

It’s not just about the unique distortion. Find out how fisheye lenses can create amazing starscapes in:
EF8-15mm f/4L Fisheye USM: My Go-to Lens for Photographing Starscapes

 

Consideration #4: Depth of field

You might have heard that full-frame cameras can produce a shallower depth of field (more visible background blur/bokeh) compared to APS-C cameras. One big reason for this is because the sensor size affects your shooting distance from the subject.

First of all, let’s recap the four factors that affect background bokeh/shallow depth of field:
i)  Distance between subject and background
ii)  Aperture setting
iii) Effective focal length
iv) Distance between the camera and the subject

What happens when we shoot with a full-frame and APS-C camera, keeping i) and ii) consistent? In the images that follow, pay attention to the size of the bokeh circles in the background and how they change.

These two images were shot with the same 50mm lens at f/1.8. We used the 1.6x crop mode on the full-frame camera so that both images have the same angle of view.

 

The bokeh circles are around the same size in both images, which shows that after the crop factor is accounted for, at the same shooting position and settings, there is no visible difference in depth of field between the images captured by the full-frame and APS-C cameras.

What if, instead of using the 1.6x crop mode for more reach, we move the full-frame camera closer to the subject so that it is the same size as in the APS-C image?

The depth of field is shallower in the image from the full-frame camera: it has larger bokeh circles. Shooting closer to the subject reduces the depth of field.

What does this tell us?

When using a full-frame camera, we often end up shooting physically closer to the subject compared to when we use the same focal length on an APS-C camera. This is usually what results in a shallower depth of field and more intense bokeh.

Find out how to recreate that sparkly background here

 

In conclusion: APS-C or full-frame camera?

Here’s a summary of the advantages and disadvantages of both types of camera

Advantages of an APS-C camera
- Often smaller, lighter, and more affordable
- Lenses designed for APS-C cameras are usually also smaller, lighter, and cheaper
- 1.6x crop automatically extends your reach
- Can usually take full-frame lenses in additional to APS-C lenses (but depending on the mount system, may need a mount adapter)

Disadvantages of an APS-C camera
- Cannot take full advantage of wide angle lenses
- Might have more visible noise when shooting at high ISO speeds in low light

Advantages of a full-frame camera
- Captures a wider field of view compared to an APS-C camera with the same lens at the same spot
- Can take full advantage of wide angle lenses
- Likely to have less noise when shooting in low light at high ISO speeds

Disadvantages of a full-frame camera
- More expensive
- Limited use with APS-C lenses

Ask yourself: how much are you willing or able to invest?

The biggest advantage of APS-C cameras and lenses is their relative affordability. If this is your first camera and you are on a tight budget, it’s possible to build a decent gear arsenal with an APS-C camera, a couple of lenses, and perhaps even a Speedlite for the cost of a brand new full-frame camera kit.

Full-frame camera systems require much more investment, but in return, they provide versatility in a greater variety of shooting conditions. That’s why so many professional photographers prefer using a full-frame camera, and why many enthusiast photographers eventually decide they need to “graduate” from their APS-C camera systems.

There’s no hard and fast rule on how a photography journey should begin. You can start small with an APS-C camera system and see how it goes, or invest in a full-frame camera kit to grow into (and grow with). Ultimately, your camera gears are tools you use for visual expression, and what matters is that you learn to use them well! That’s what SNAPSHOT is here for.

Happy shooting!

 

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