The size of the sensor in a digital camera can have a huge impact on the quality of the images it can produce. I’m not talking about the number of megapixels here but its actual physical size.
At the smallest end there are camera phones and compact cameras which, while not comparable to DSLR’s, can produce remarkable images from very small sensors. However a sensor of this size is never going to be able to provide a shaloow depth of field, to isolate the subject of a photograph which is often the hallmark of a professionally taken image.
Camera systems like the Sony NEX range and Nikon One system usually have a sensor known as the 4/3rd’s size. These provide some improvements in terms of depth of field, particularly when paired, as they often are, with fast lenses which have wide apertures such as f2 or f1.4.
The vast majority of digital SLR cameras have an ASP-C or cropped sensor. This is a sensor that is approaching the ‘full frame’ size and can provide excellent low light performance and a shallow depth of field. Again, the use of professional ‘fast glass’ with apertures of f2.8 or larger are a great help here. A DSLR with a cropped sensor is usually sufficient for the average photographer to achieve great pictures. Moreover, it would be a mistake for most people to invest in a more expensive full frame camera body before they have bought a good selection of fast lenses. A full frame camera with a cheap lens is a bit like owning a sports car that’s stuck in first gear! Perhaps an exception to this would be a landscape photographer who may not be looking for a shallow depth of field and can take advantage of the sharpness of a lens, stopped down, paired with the additional clarity and field of view of a full frame camera.
So what do we mean by full frame? The sensor in a full frame camera is of comparable size to 35mm film and is the choice of most wedding photographers and photojournalists. If you are looking for a camera that can offer you the highest quality images, with the shallowest depth of field and best low light performance then a large sensor will help. The latest cameras like the Nikon D600 and Canon 6D are putting full frame cameras within reach of more users and are delivering stunning results.
Sensor sizes don’t stop at 35mm though. Many professionals will choose a medium format camera, particularly when working in a studio for an even greater quality of image. The creative possibilities and ‘look’ of medium format make them a popular choice for fashion and portrait photographers.
My own decision to step up to full frame was dictated by the very reasons outlined above. As a wedding photographer, the low light conditions of most churches and the need for the camera to focus in the darkness of the late night party mean that, once I had made enough money to reinvest in my equipment, a full frame camera was the obvious choice. However, I didn’t make the leap until I had invested in some high quality lenses and felt I had reached the creative limits of my existing camera.