As a photography enthusiast, you must have noticed the recent trend to produce cameras with ‘full-frame’ sensors. By full-frame, we mean that the format or size of the sensor is 24 x 36 mm or something very close to it. Let us go back a little in time and look at the origins of this term. We will see later the impact of the full-frame sensors on images.
Film that was 35 mm in width and used in movies was adopted by some camera manufacturers for still photography. To facilitate easy loading, the film came spooled in cassettes (Picture 1) and was also known as ‘135’, this being an internal designation of the Eastman Kodak company, though it was used by everyone later. There are two interesting points here. First, when shown in a theater, this film runs vertically.
However, in still cameras (called 35 mm cameras), it runs horizontally. Second, for the former the active image area (frame) is 22 x 16 mm whereas the corresponding numbers for the latter were 24 x 36 mm. The movie frame was called ‘single-frame’ and that of stills ‘double-frame’ or ‘full-frame’. However, these words were seldom used during the film era.
While several frame sizes/formats were tried with the 35 mm film, the aforementioned frame of 24 x 36 mm promoted by Leica became very popular. While initially thought to be not good enough for serious work, steady advances in optics and film made this format the choice for almost all applications. So, the 24 x 36 mm format reigned supreme for many decades till D-SLRs made an appearance.
First D-SLRs due to the then technological and manufacturing limitations adopted a sensor size of 24 x 16 mm. This was the same as another film format called APS-C (now defunct) and is used to specify this format.
Subsequently, as technology advanced, latter D-SLRs adopted the same format of 24 x 36 mm for their sensors. Naturally, the name ‘full-frame cameras’ was adopted, and this also helped to distinguish these from the earlier D-SLRs with smaller sensors. Smaller sensors are often called ‘cropped’ sensors. Cropped means smaller than full-frame, and there are many sizes that fall under this category (Picture 2). In this article, we will discuss about only one size of cropped sensor, that is, APS-C size (unless otherwise noted), but the conclusions we draw can be extended to other formats as well.
Also used are the terms FX and DX for full-frame and APS-C cropped formats respectively, but these names are proprietary to Nikon. There are formats even larger than full-frame called medium format, but we will not be dealing with those in this article. For the sake of brevity, we will call a camera with a smaller sensor a cropped camera (instead of ‘camera with a cropped sensor’) and that with a full-frame sensor, a full-frame camera.
Now that we know what full frame and cropped sensors mean, let us look at the technical implications and their effect on the image quality. The rest of the article will deal with these two important issues in detail.
Angle of view and crop factor
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