Tuesday, July 9, 2019

Different, not Better

The master of candid photography, Henri Cartier-Bresson had described the camera as a sketch book, an instrument of intuition and spontaneity. This emphasises the need to understand our photography gear, know its strengths and weaknesses  so as to master its operation.
          Before buying a Digital Single Lens Reflex (DSLR) camera, many photo enthusiasts keep questioning  which way to go. Full frame or crop sensor  and now their attention is also drawn by the mirrorless camera. I think its better not to discuss the mirrorless for the time being as for many the choice is already confusing.
          The terms crop-sensor and full-frame refer only to the size of the imaging sensor inside a camera. The full-frame sensor is of the same size of a piece of 35mm film, the 24mm x 36mm format. On the other hand, any size of sensor  less than 24X36 mm is called crop sensor. It is also known as the APS-C,(Advanced Photo System). For instance, Nikon’s  full frame  sensor  is of 24X36 mm and the camera is  categorized as FX. Its crop sensor (camera body categorized as DX) is of the size of about 24 X16 mm. The crop factor is 1.5 x. Canon’s cameras  are also of full frame and those of crop sensor have crop factor of  1.3x and 1.6x.Other camera manufacturers also make crop sensor cameras, but their sizes differ.
Both the crop-sensor and full-frame cameras have their own advantages and disadvantages. For instance, in case of a crop-sensor camera of Nikon, the angle of view of a 50 mm lens  will be 75 mm whereas on full frame sensor its effective focal length will remain unchanged. Today, the high-end crop sensor cameras have the potential to provide image quality similar to that of a full frame. But it’s very difficult to point out the difference because it is simply negligible. Thanks to the improved sensor and processor technology.
While most of the sports  and wildlife photographers as well as photojournalists prefer crop-sensor camera to get an extra reach, the landscape and architecture photographers opt for full frame because of its potential to cover wide area. A crop-sensor camera can achieve similar wide view with a wide angle lens made for a crop sensor camera.
The question is, if now the gap between the image quality of both kind of cameras is negligible, why the photographers still feel they would upgrade to a full frame camera. It was in early 2000s that DSLRs began to replace film based Single Lens Reflex (SLR) cameras. The initial DSLRs used to have cropped sensor as it was not easy to make full frame sensor because of its high cost. Later on some camera manufacturers began to manufacture full frame cameras based on the standard 35 mm film format. We have among us many photographers who have enjoyed making images with medium format or large format cameras and the availability of full-frame camera is a boon for them. The crop sensor being smaller  than the standard 35 mm film format , was  considered as an a downgrade.
Practical Implications
Size-The basic difference between the two is of the size of the sensor as a result of which the camera body size also differs. The crop sensor camera is smaller in size and lighter in weight  whereas the full frame camera is bigger and comparatively heavier. Its not that the bigger sensor increases the weight of the camera, but the sensor size increases the dimensions of the camera body  and so makes it comparatively bigger and expensive. The lenses of the full frame camera are also bigger, heavier and expensive.  
The size of the camera  sensor makes interesting effect on various aspects like ISO, depth of field, apparent focal length of lenses and dynamic range, but this does not make us judge how good or bad a camera is. They are different. 
ISO : Higher the number of ISO, greater is the sensitivity of sensor. However, all digital cameras have base ISO which   can be 50 or 100 or 200. Today, most of the crop-sensor cameras significantly outshine their forebears from just a few years ago when people did not like to shoot even at ISO 800 or 1600. The facility of Auto ISO is a remarkable addition.
A full frame sensor provides high ISO and better low light performance, a broader dynamic range and yields a higher quality image as compared to that of a crop sensor. Thanks to the ongoing improvement in technology as nowadays even some of the latest crop sensor cameras are capable of high ISO performance.
Depth of Field: Remember the bigger is not always better. Depth of field  is defined as the zone of acceptable sharpness, which is in front and back of the subject in focus. It can be shallow or deep. The sensor size affects apparent depth of field. When shooting full-frame we get the benefit of a shallower depth of field, which is often liked by the portrait photographers. Those engaged in architecture and landscape photography also prefer full- frame cameras because that gives them wider field of view.
Focal Length: It is not a measure of how long or short  a lens is physically, but it is the distance in millimeters from the optical centre of a lens to the imaging sensor when the lens is focused at infinity.
If a full frame  and a crop-sensor DSLR take the same image from the same distance, with the same lens and point of view, the crop sensor camera will capture a tighter field of view than the full-frame camera. The focal length measurements of lenses being based on 35 mm standard, a crop sensor crops out the edges of the frame, which effectively increases the focal length.
Dynamic Range- It is the range of value between light and dark areas. We see wide range of intensity levels in real scene ranging from direct sunlight to shadows. Because of larger pixels, full-frame cameras  have a broader dynamic range in general, making them better equipped to capture the full brightness range of a scene that features both extreme areas of dark shadows and bright highlights, as well as mid tones. 
Many photographers like to shoot landscapes with a full frame camera because they need maximum wide area in the frame, leave aside other factors. However, when one is to choose between  the two for landscape photography, the answer is, "It’s your choice." Just to ponder over the issue, if one wants to have maximum depth of field for landscapes, it can be achieved with a crop-sensor camera. Also, while shooting at  the same angle of view, on a  crop-sensor and full-frame cameras, if the aperture is f/11 on crop-sensor one may have to use f/16 on a full-frame  to ensure sharpness from foreground to background.
          All said and done, no doubt the full frame camera will yield images of higher resolution  and would  have better low-light performance, but at a considerable price. On the other hand, the crop-sensor camera will help in achieving extra reach at a comparatively low cost. As Nikon has retained  “F” mount for its lenses for both kind of cameras, the full-frame lenses will work properly on crop-sensor cameras, but the reverse has limitations.
Today, many photo-enthusiasts remain keen to upgrade to full-frame with the hope to improve their image quality. But this assumption is not necessarily true. As said earlier, advancement  in  technology   has  narrowed the gap between the image quality and noise levels between full-frame and crop-sensor cameras.
In full frame cameras, the sensor space is used to make each pixel bigger. For example, a full-frame camera with 24 megapixels has bigger pixels spread over a larger sensor area than a crop-frame camera with an equal number of  megapixels. Bigger pixels absorb more light photons, which increases dynamic range in the photo. Greater dynamic range means there will be somewhat more detail visible in dark areas, and less noise. Therefore, better performance in low light.
Here a word of caution. Its not only the high cost, size and weight of the full-frame camera that matters, but also the care with which the images are made. Resolution of most full-frame sensors is so high that it exposes any shortcoming in technique and clarity of image. Thanks to the advancement in technology, none of the full-frame or crop-sensor camera is better, they are different.
          Now the camera manufacturers are   competing with each other in adding more pixels to their megapixel cameras. Is it a  marketing gimmick or do we really need so many pixels. Its high time for the photographers  to  be conscious of  possible compromises, if any.
Subhash Sapru

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