APS-C sensor

The APS-C dilemma

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Should you buy a camera with an APS-C sensor, or a full-frame?

This argument has been going on for a number of years now, and still divides the photographic community. Is APS-C better than full-frame, or is it sub-optimal? Well, I think it’s all about perspective. APS-C, along with Micro-Four-Thirds are frequently viewed as mere crop-sensors, a designation that only exists because we perpetuate the falsehood that full-frame offers the “standard” sensor size. This stems from the fact that 36×24mm was the standard film size before digital cameras came along. As digital cameras evolved, “full-frame” became the name for the sensor size that matched a 35mm negative.

However we are at the point in time where each sensor size should be considered on its own merits, (and pitfalls) without unnecessary inference that it is a mere “stepping-stone” to a full-frame. Identifying an APS-C sensor, which has a size of 23.6×15.7mm, as “just a crop” sensor does not give the camera the kudos it deserves. The problem lies in every aspect of how these cameras relate to one another, but manifests itself best in lenses.

APS-C versus full-frame camera
The physical differences between APS-C and full-frame. The full-frame Leica SL3 is nearly twice the weight of the APS-C Fujifilm X-T50, and has a much bigger form factor.

Most APS-C sensors have a crop-factor of 1.5 (except Canon which is 1.6). This means lenses function a little differently than on full-frame lenses. Now a 50mm lens is always 50mm, regardless of the system it is associated with − it’s how that 50mm is interpreted in relation to the sensor that is important. For example a 50mm lens is a “normal” lens for a full-frame camera, while in APS-C land a normal is going to be a lens with a focal length of 33-35mm. A 50mm lens on an APS-C sensor will give a smaller picture than a full-frame, because well obviously the sensor is smaller. So an APS-C 50mm has the same effect as a 75mm lens on a full-frame camera in terms of what is in the picture.

Some basic visual comparisons of APS-C versus full-frame

There are obviously things that full-frame sensors do better, and things that APS-C format cameras do better. Image size is the first, which is purely the result of full-frame cameras having more photosites on their sensors. With the evolution of pixel-shifting technology this may be a mute-point as super-resolution images are already available on some systems. Full-frame cameras also tend to have better dynamic range and low-light performance. This is because photosites are often bigger on full-frame cameras, so they can collect more light and better differentiate between light intensities. This means they work better in low-light situations introducing less noise. But digital cameras rely on software to turn the data from photosites into the pixels in an image, and so as software improves, so too will things like noise suppression algorithms in APS-C.

How lenses function on APS-C and full-frame lenses

But not every full-frame has larger photosites. For example a Fuji X-H1 camera with a 24MP sensor has 6000×4000 photosites, with a photosite pitch of 3.88μm. The Sony a7CR has a 61MP sensor (9504×6336) with a pixel pitch of 3.73μm, which is actually smaller than that of the APS-C sensor. So more pixels, but perhaps a low-light performance that isn’t that much better. And what is anyone going to do with images 60MP in size? Post them on the web? I think not.

featureAPS-Cfull-frame
low-light performancegoodexcellent
depth of fielddeepermore shallow
lens availabilitylarge selectiongood selection, fewer third-party lenses
lens costaffordablemore expensive
portabilitylight, easy to carryheavy, bulky
dynamic rangeslightly reducedwider
applicationsstreet photography, sport, wildlife, travellow-light, studio, landscapes, portrait
camera body costtypically affordableusually expensive
wide angle lenses18-23mm28-35mm
normal lenses26-38mm40-58mm
A comparison of some of the characteristics of APS-C versus full-frame

Full-frame cameras, just like medium-format cameras are for people who need the things they provide – high resolution, low-light abilities, etc. Many people tend to correlate a full-frame camera with high quality because of its sensor size, but quality isn’t necessarily associated with high-resolution images. Yes, more data captured by a camera means more detail in an image, but that doesn’t automatically mean that APS-C sensors (or even MFT) are inferior.

Most non-professional photographers don’t need huge image sizes, just like they don’t need a Leica. APS-C cameras are considerably lighter, and more compact than their full-frame brethren. APS-C lens are also cheaper to purchase, because they are easier to build, and require less glass. In all likelihood there is also a broader ecosystem of third-party lenses for non-full-frame cameras as well, as they are cheaper to manufacture. Over time as newer sensors evolve, APS-C may be well positioned to take a more prominent role in the camera world.

Further reading:

Choosing the right digital lens can be challenging

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Choosing a digital camera, and a sensor size is one thing, but I think the thing that really stumps people is choosing the most appropriate lenses to use. Of course for the amateur photographer, what the lens will be used for may be the most important consideration. Travel? Landscapes? Street photography? The task is always made easier if there are some constraints on the number of lenses available. For example the range of lenses available for Micro-Four-Thirds, or even Fuji-X cameras has always been a little bit constrained, well until recently with the expansion of 3rd-party lenses.

So how do you choose the right lens? Like vintage lenses, digital lenses are principally chosen based on focal length (which advocates their use), and speed, i.e. aperture size. In addition there is cost, and “extras” such as weather sealing, and stabilization. The problem comes with the variety of lenses available – consider the long list of Fuji-X lenses, many of which are 3rd-party. Which one should you choose? Do you choose a prime or a zoom, a Fujifilm, or a third-party? Do you need an 8mm APS-C lens? Would 13mm be better? What about 16mm? Is manual focus okay, or would you prefer auto-focus? It’s not easy, even with the myriad of videos reviewing lenses.

I’ll concentrate on Fuji-X here, because it’s at the heart of my current lens dilemma (my camera is a Fujifilm X-H1). Now my photography is a mixed bag of street, landscape, architecture and travel. I currently have the 23mm f/2 R WR (which is a FF 35mm equiv.). Now I’m looking to expand, primarily a wide-angle lens. Here are some of the typical focal lengths for Fuji-X (APS-C sensor), and their applications. Measurements in ( ) represent the full-frame equivalences.

  • 50-56mm (75-85mm) – Good for portraiture.
  • 33-35mm (50-53mm) – Good for general photography, portraiture and cityscapes.
  • 23mm (35mm) – The upper end of the wide spectrum, provides more scene than the 33mm, but without the distortion of wider focal lengths. Good for street photography.
  • 18mm (28mm) – The standard choice for landscapes (and sometimes architecture), providing a relatively wide angle of view, without introducing obvious distortions.
  • 14-16mm (21-24mm) – The common lower end of the wide spectrum, good for very broad landscapes. Can include some noticeable perspective distortion, especially if the camera is tilted.

Beyond that we begin to move into the ultra-wide focal lenses, of which there seem to be quite a number. 11-13mm (16-20mm) lenses encompass more of the scene than can be seen with normal vision, so there is an innate sense of exaggerated perspective. Subjects close to the camera appear quite large, with the relative size of more distant subjects reducing quickly with distance. These lenses can be ideal for photography where the distortion does not impact the aesthetics of the image.

Various Fuji (APS-C) lenses and their associated angles of view. (Photo taken from Belvédère Kondiaronk lookout on Mont Royal, Montreal)

In reality, going down this rabbit hole has led me towards the 16mm, and possibly something like a 33-35mm. I have enough vintage lenses to cover the 50mm+ spectrum, and this makes sense as I don’t envision using them that often. And I’m going to stick with prime lenses. Some people really like zoom lenses because of the flexibility they allow, but I find I always seem to stick to one focal length – the 12-40mm on my Olympus camera used when travelling is perpetually set at 12mm (24mm). There are other compromises as well – weight can be an issue, as well as slower apertures.

Choosing a digital lens is challenging, especially for the hobbyist photographer. There are a lot of options, regardless of the sensor. Even Micro Four Thirds also has a long list of lenses. If someone is unsure, then I suggest starting with lenses from the camera manufacturer. As to focal length, choose a lens that provides the most optimal angle-of-view for the application you are most interested in. For example, if you shoot with an APS-C camera, and your focus is street photography, then a 23mm (35mm) lens is the most optimal solution.