Making Sense of Sensors – Full Frame vs. APS-C
There is more to a full frame sensor than simply being bigger than an APS-C one and it is not necessarily the best choice for all types of photography. Find out why in this in-depth article on the differences between full frame and APS-C cameras and lenses.
It’s hard to find a photographer these days who doesn’t have a digital camera, where an electronic sensor replaces film as the means of recording the results of the shutter click. However, many of the terms used in film photography persist into the digital era, such as ‘full frame’. In this article we will explain the terminology and how the size of the sensor affects the quality of the images taken.
Full frame Sensor Cameras
For those new to photography, let’s first get some basic definitions out of the way. 35mm film was the dominant standard in still photography until digital photography took off. The term ‘full frame’ refers to the sensor being the same size as a single negative (or frame) on a 35mm roll of film ie 24 x 36mm. So, the image sensor inside a full frame camera body is 24mm high and 36mm wide. The ratio of width to height of a sensor is known as the aspect ratio which governs the proportions of each image. With a full frame camera (and 35mm film) it is a ratio of 3:2.
APS-C Sensor Cameras
APS stands for Advanced Photo System. This is a film format that was introduced in 1996, but has since been discontinued. APS film frames measure 16.7 x 30.2mm, but there are three different APS digital image formats: H (high-definition), C (classic) and P (panorama). All three are smaller than the original APS and 35-mm film size, hence the term ‘cropped sensor’. The H format is the same ratio as the entire APS negative, while the C format has an aspect ratio of around 3:2, the same as in a full frame camera. The exact size of an APS-C digital sensor varies slightly depending on the camera manufacturer.
APS-C images sensors can be found in most digital SLR, mirrorless and compact systems cameras. It is no wonder, then, that the selection of APS-C lenses and camera bodies on the market is very large compared to their full frame counterparts. All ZEISS lenses are optimized for full frame image sensors, with the exception of Touit.
Lenses are designed to suit the sensor type
The APS-C format is the one most commonly found in digital SLR, mirrorless and compact systems cameras. This has led to a wider choice of lenses being manufactured to suit APS-C sensors.
All ZEISS lenses are optimized for full frame image sensors, with the exception of the Touit range.
APS-C sensors: cropped images
Because an APS-C image sensor is smaller than a full frame sensor, APS-C cameras have a smaller area to capture a scene. In other words, the scene is ‘cropped’, as illustrated below.
With an APS-C sensor, the angle of view is narrower. This creates the impression of being zoomed in more. Although the depth of field remains the same in both cases, the background is “sharper” than the same shot taken with a full frame sensor and the same aperture. So by using different image sensors, you have created two very different images.
The crop factor
The crop factor allows you to figure out what the field of view would be in a 35-mm film format equivalent camera based on the actual focal length you are using on a APS-C camera. It also helps you compare lenses. The crop factor is always calculated by dividing the full format size by the size of the APS sensor. Let’s take an example.
Suppose your APS-C image sensor is 25.1 x 15.7mm. If you divide 36mm by 25.1mm (36/25.1), you get 1.43. That’s the crop factor. If you put a 70-mm lens on a digital SLR camera that has an APS-C image sensor and multiply this focal length by the crop factor (70 x 1.43 = 100), you would produce the same field of view as if you were using a 100mm focal-length lens on a full frame camera. Crop factors for digital SLR cameras can vary between 1.3x and 2x. The higher the crop factor, the more zoomed in the image will appear.
Which sensor is ‘better’?
It’s a myth that full frame cameras and lenses are, by definition, better than their APS-C counterparts. Granted, due to the larger sensor size – and higher price tag – professional photographers mainly use full frame cameras. But the choice of APS-C or full frame is not about price or size. Ultimately, it depends on your goals, ideas, and the kind of photography you like to do.
Staying in the background
One big advantage of APS-C sensors is that the cameras that have them are smaller and lighter than a full frame camera. So if you like to do street photography, compactness may be just what you need. You’ll be able to capture the atmosphere and your subject while remaining inconspicuous.
APS-C cameras and lenses are a good choice for street photography as they are smaller and lighter so less obtrusive.
Depth of field
A crop-sensor camera also comes in handy for macro shots. Recall that depth of field (DOF) is the distance between the closest and furthest parts in an image that will appear in focus. At the same aperture and for the same field of view, an APS-C sensor will have a higher depth of field than with a full frame camera.
A full frame sensor camera and lens will have less in focus for a given aperture and field of view than an APS-C combination, allowing more creative effects.
APS-C cameras enable you to fill the frame with your subject from a greater distance, so the images will look more zoomed in than if they had been with taken with a full frame camera. This can be an advantage when you cannot, or should not, get too close to your subject, such as wildlife, an athlete or another source of action. An APS-C sensor magnifies telephoto lenses, enabling you to get “closer up” with these. A 200mm lens on an APS-C camera will act like a 300mm lens on a full frame camera.
Advantages of full frame sensors
That said, full frame camera systems offer several distinct advantages over APS-C sensors. For starters, you’ll have more control over the depth of field because you’ll need to move in closer to your subject. This could be important for portraits or if you want to create other aesthetic effects.
A full frame camera/lens combination also delivers better image quality. The reason is the pixel pitch: a larger sensor with the same number of pixels means each individual pixel is larger; this allows more light to be captured. Hence, full frame systems also perform better when the light is weak, enabling you to confidently raise your ISO settings. For night photography, full frame sensors win hands down over APS-C sensors.
Full frame systems also produce more finer details because the pixels are larger, creating a better dynamic range than an APS-C sensor would with the same number of pixels. Because of a full frame sensor’s larger size and the larger field of view it projects, a full frame lens/camera combination is also more suitable for wide-angle shots, which is relevant for architectural, landscape or product photography.
A full frame camera and lens is the best choice for wide-angle landscape images.
Mixing and matching
Given the ubiquity of APS-C lenses and camera models, how much mixing and matching is possible between both systems?
All full frame lenses can be used on an APS-C camera with the same bayonet, but you will still only get a cropped frame. Putting an APS-C lens on a full frame camera will also produce a cropped scene. This will cause vignetting (black corners) on the image as light can’t reach into all the corners. Fortunately, some full frame cameras recognize an APS-C lens and automatically switch to a crop mode. That happens if you put a Touit lens on a Sony full frame camera.
Investing for the future
Both full frame and APS-C sensor formats will continue to exist alongside each other. That said, upgrading to full frame lenses and camera models will always be a winning recipe for maximum creative potential. Full frame is also a solid investment in the future because full frame systems never become obsolete. Future innovation in both types of sensors will be driven by the quest for even higher resolution, a trend already visible in video.
Full frame vs APS-C sensors and lenses summary
Which will suit you best?
|Situation||Which is best?|
|Street photography||APS-C, smaller, lighter cameras|
|Macro photography||APS-C, greater depth of field|
|Sports, wildlife||APS-C, greater reach for a given focal length|
|Architecture, landscape||Full frame, larger field of view, more suitable for wide-angle shots|
|Night photography||Full frame, sensor captures more light|
|Creative flexibility||Full frame, greater ability to choose a narrow depth of field|
|Superior image quality||Full frame, higher pixel pitch|