Sensors vs Film
Digital camera sensors are smaller than film in all cases, except for full frame digital single lens reflex (digital SLR or DSLR) cameras, which are equivalent to 35mm. When taking the same photograph on 35mm film and a common digital camera, the digital camera will have closer framing with a lower quality image when compared with the 35mm film image. This is due to a feature called the aspect ratio.
Aspect Ratio
Aspect ratio is defined as the longest dimension to the shortest dimension in a frame. For example, 35mm film measures 36 by 24mm and so has an aspect ratio of 36:24, or more commonly stated, a 3:2 aspect ratio. Single Lens Reflex cameras use 35mm film and are a readily available, popular format. Some Digital Single Lens Reflex cameras (DSLRs) mimic 35mm and provide the same 3:2 aspect ratio. These are called full frame DSLRs.
Compact digital cameras and some DSLRs, on the other hand, provide a 4:3 aspect ratio. This is also the common ratio for computer monitors and televisions.
The Crop Factor Effect
Since digital sensors are smaller than film frames, the same lens will have a different effect on the same image in a film camera versus a digital camera. For example, a 28mm lens on a film camera is considered wide angle, but used on a camera with 4:3 framing, it would be like using a 55mm.
Aspect ratios are often referred to differently when discussed in terms of crop factor. A 1.6x crop factor is another way of expressing that a camera has a 4:3 aspect ratio. This is simply the length divided by the width of the aspect ratio. Therefore, a 50mm lens on a camera with a 1.6x crop factor (4:3) is equivalent to an 80mm lens on a camera with a 1.5x crop factor (3:2).
Types of Film
35mm (3:2) is the most popular film type. It is versatile, does not require a large, cumbersome camera and provides good image quality.
APS (advanced photo system) did not gain popularity due to innovations in digital photography that made its intended flexibility seem antiquated before it reached the consumer markets on a large scale. It was intended to be more versatile than 35mm by providing options for aspect ratio selection, such as panoramic.
Medium format film is intended for Twin Lens Reflex cameras (TLR cameras), which are larger, bulkier, and more expensive than SLRs. The increased size accommodates larger negatives, however, which provides better quality in addition to multiple aspect ratios in its common film types. Some examples of medium format film are 6x4.5cm negative, 6x17cm panoramic film and 6x7cm negative, which is the most popular medium format option.
Sheet film (large format) comes in 5-by-4-inch and 10-x-8-inch negatives. This film is expensive, intended for large cameras and is costly to process. Much like with medium format however, it is high end film that provides impeccable quality and clarity. Large format cameras can be hard to come by and are most often seen in fine art and professional photography.
Ratios for Print
When printing a 4-by-6-inch print from a digital photograph, cropping will often occur at the edges of the image because a 4-by-6-inch print requires an image with a 3:2 aspect ratio and most commercial digital cameras use a 4:3 ratio. While this may not affect the specific image, it can often crop out important parts of an image.
In short, if aspect ratios do not match the desired print size, arbitrary cropping at the edges will occur depending on the crop factor.
Tags: aspect ratio, 35mm film, camera with, crop factor, digital camera, Lens Reflex, Lens Reflex cameras
