That’s a logical question. After all, the APS-C format has already died once—albeit in its original Advanced Film incarnation that was killed off by the rise of digital compact cameras. But unlike their film-based ancestors, which included a handful of APS-C SLR models, the proven advantages found in APS-C DSLRs may give them a reprieve from the same fate. Let’s take a closer look at those benefits, especially as they relate to pros who demand more than improved low-light performance and depth-of-field separation from their camera systems.
For starters, APS-C DSLR bodies can be built smaller and for less than similar-featured, full-frame DSLR bodies, period. That’s because nearly all of the components involved in the camera design and exposure system are larger and more expensive to manufacture in full-frame cameras. Topping the list is the cost differential between the full-frame sensor and APS-C sensor, with full-frame sensors typically priced several hundred dollars more per chip due to the difficulty faced in manufacturing a larger-area sensor. (Approximately 30 full-frame sensors can fit on an eight-inch wafer compared to over 100 APS-C sensors, and defects are more likely in the full-frame manufacturing process.) Obviously, the cost of manufacturing full-frame sensors has come down over the years as resolution has increased or we wouldn’t see affordable 20-plus-megapixel models like the Nikon D600 or Canon EOS 6D. The same can be said about APS-C sensors. However, other component costs for a full-frame camera have remained higher, including the prices for the larger reflex mirror (Canon and Nikon models), SLT mirror (Sony), optical viewfinder, shutter blade, internal AF motor and even the batteries (more power needed to operate the mirror assembly, shutter and AF).
In this increasingly competitive space, manufacturers can’t hide or absorb the cost of building the camera in hopes that photographers will buy more lenses and accessories to make them profitable. So don’t expect the same features and performance between similar-priced APS-C and full-frame HDSLRs. For the same price, the APS-C camera likely will include faster focusing systems, better burst performance, better build, additional manual controls over video, etc. The question pros must ask is whether the increased low-light performance, typically brighter viewfinder and increased depth-of-field separation provided by a full-frame DSLR will be enough to offset the missing features, smaller sizes and lower costs of APS-C models.
Wait! We’re forgetting the other half of the DSLR equation: the cost, size and compatibility of lenses! If you’re moving up from an APS-C-based DSLR, you’ll notice that lenses optimized for use on full-frame cameras are larger and more expensive than their APS-C-optimized equivalents. Again, material costs add up, but manufacturers also know that pros are more willing to spend more for a good lens (or they can blame the higher prices on economy of scale). Sure, a full-frame camera provides a wider field of view for any given focal length than an APS-C camera, but you may not be able to fit as many lenses in your camera bag (or budget), and if you’re a Canon shooter, you also lose backward-compatibility with your existing stock of lightweight EF-S lenses. (You can mount Nikon DX lenses on FX models such as the D600; however, you can’t mount a Canon EF-S lens on full-frame models such as the Canon EOS 6D without an adapter because of differences in back-focus distance and interference from the mirror.)
Most APS-C DSLRs, on the other hand, not only accept smaller, more affordable "digitally optimized lenses" such as Nikon’s DX, Canon’s EF-S, Pentax’s DA and Sony’s DT series, but are also backward-compatible with the respective brand’s full-frame lenses that may harken back to the film days—albeit with a 1.5X to 1.6X cropping factor (see the sidebar). When full-frame lenses are mounted on a compatible APS-C model, the sensor is covered by the central sweet spot of the lens, resulting in the best performance match and minimal edge distortion or light falloff. However, on full-frame DSLRs, you’re more likely to notice the shortcomings of a full-frame lens—especially lenses designed during the film days—at the widest apertures and toward the corners of the image. You’ll also notice that the AF zone area on a full-frame camera generally covers less of the field of view than it does in an APS-C camera. That’s because camera manufacturers tend to use similar focusing engines across both DSLR formats, and the wider field of view provided by a full-frame camera means a proportionally smaller AF zone in the center of the viewfinder. However, that gives a focus-tracking advantage to the APS-C DSLR, since the AF zones cover more of the image area and can lock onto moving subjects on the extreme right or left before a full-frame camera’s AF system can.
For nature and sports shooters, the added 1.5X or 1.6X cropping factor afforded by any lens on an APS-C DSLR is a plus, as it allows them to get closer to a subject without spending more on a heavier supertelephoto lens (for example, a 100-300mm ƒ/4 lens becomes a 150-450mm ƒ/4 equivalent lens at half the size and weight) or turn a bright 50mm ƒ/1.4 lens into a great 75mm-equivalent ƒ/1.4 portrait lens. In addition, adding a sensor-based image-stabilization system to a DSLR, such as those found in Sony and Pentax models, or even a lens-based optical-stabilization system like those sold by Nikon and Canon, can be done more effectively and at a lower cost with an APS-C camera or lens than a full-frame camera or lens. You also may notice that the image-stabilization system and the autofo
cusing system are slightly quieter on APS-C cameras and lenses due to the mechanical differences.
Improved lens designs for APS-C DSLRs also have increased the number of ultrawide-angle offerings, allowing wider fields of view that once were the exclusive domain of full-frame DSLRs. In fact, a typical image-stabilized 18-55mm ƒ/3.5-4.5 kit lens, with an equivalent wide-angle to telephoto field of view of 24-80mm, now can be purchased for $100 to $200, yet ranks as one of the sharpest lenses available for APS-C models. Compare that to the full-frame Nikkor 24-85mm ƒ/3.5-4.5G ED VR kit lens introduced for the Nikon D600, which costs $500.
One last note on the lens front: As manufacturers continue to pack more pixels into their full-frame sensors than their APS-C sensors (and they will, won’t they?), photographers may start to notice a greater drop in resolution at apertures above ƒ/11 due to lens diffraction. Unfortunately, diffraction affects all lenses equally due to the physics of light and becomes more noticeable in high-resolution sensors (above 20 megapixels) and at apertures above ƒ/11—something to consider when you’re trying to squeeze out more depth of field in a scenic or macro shot.
The bottom line? The APS-C class of HDSLRs looks like it’s going to be around for a long time based on its relative cost, size and several performance advantages over full-frame HDSLRs. In addition, there are more than enough APS-C and full-frame lenses available to satisfy most pros and advanced amateurs who want to stick with APS-C—and those same lenses can be used on a growing number of APS-C-class camcorder models and several interchangeable-lens compact cameras.
Michael J. McNamara is a renowned expert on digital cameras, printers and color management systems. During his 20-year editorial career, McNamara has written hundreds of articles on all aspects of photography and technology. He’s also the editor in chief of the McNamara Report, www.mcnamarareport.com.
Full Frame Vs. APS-C:
The Cropping Factor Explained
| What’s a lens-cropping factor, and why don’t full-frame cameras have one? The lens-cropping factor is a shortcut used to explain and predict the different fields of view captured by full-frame and APS-C cameras using similar focal-length lenses. Essentially, full-frame cameras actually have a cropping factor, but it’s a 1:1 factor compared to factors ranging from 1:1.5 to 1:1.6 in most APS-C cameras, and typically written as 1.5X (Nikon, Pentax, Samsung, Sony) or 1.6X (Canon).
In the early days of digital, the cropping factor often was erroneously labeled the focal-length magnifier, as if it referred to the same changes one might expect when using a teleconverter to increase the reach of a lens. These changes included a reduction in a lens’ maximum aperture, plus decreased field of view and depth of field at any given focal length and aperture. But with digital cameras, only the field of view varies, as lens focal length is based on optical formulas that don’t factor in the size of the camera sensor. Therefore, a lens’ maximum aperture and depth of field at any given aperture don’t vary based on sensor size; only the field of view changes.
An easy way to picture this relationship is to imagine two different windows set in the same wall. Stand inside at the same distance from each window and look through the smaller window (APS-C), and you’ll see a narrower field of view compared to the larger window (full frame), but the exact same depth of field and scene brightness.
To determine the cropping factor on any interchangeable-lens camera, you must divide the diagonal length of a full-frame sensor (43.3mm, the same as 35mm film) by the diagonal length of the smaller APS-C sensor. For APS-C sensors in a Nikon camera, the diagonal is 28.9mm, resulting in a cropping factor of 1.5X, while on a Canon APS-C-class sensor, the diagonal is closer to 27mm, resulting in a cropping factor of 1.6X.
Once the cropping factor is known, it can be multiplied by the focal length of the lens to determine the equivalent field of view recorded by the sensor. For example, a 50mm lens placed on a Nikon D90 (APS-C sensor) will show the same field of view on captured images as a 75mm lens mounted on a full-frame camera (50 x 1.5). However, the depth of field at any given aperture will remain the same for each of the captured images, while changing the actual focal length from 50mm to 75mm on the full-frame camera will result in a slightly decreased depth of field.