Digital Cameras: Crop vs ‘Full Frame’

There are cases where the rapid evolution of technology means that terms can lose connection with their original meaning.  ‘Crop’ and full frame are clear examples.  Should we go back to the original meaning, or embrace using the original term in ways that evolve further and further from that original meaning?


Film Cameras

studijskifotoaparatFilm Cameras were invented in the 1880s, but it was in around the 1920s that standard film sizes became popular, which allowed specialist camera brands to emerge.   No film camera is of any use unless film for the camera was readily available, but with film already available, a company could now manufacture only cameras and lenses.  Eventually, specialisation allowed for an ecosystem of specialist camera brands (e.g. Nikon, Canon, Ricoh, Pentax, Leica, Hasselblad etc) and separate specialist film brands (eg Kodak, Fuji), who often made both film for general use, and for their own brand cameras.

nikonfThe most common standard sizes to emerge were 35mm (suitable for consumers and newspaper photography), the larger medium format for magazine photography and studio work, and even larger large format (4inches x 6inches and larger)  sizes for specialist high quality work.  As film qualify improved, medium format and particularly 120mm and 220mm film took over from large format in almost all use cases.pentaxshift

Standard film sizes, meant lenses were all manufactured to produce an image size optimized for a specific film size, mostly 35mm lenses or medium format lenses.

Pre ‘DSLR’ Digital Cameras

1996, 640×480 resolution Sony DSC-F1

The first digital cameras were either:

– not really alternatives for ‘real’ photography, very expensive specialist professional
– or cameras made by Kodak combining a Nikon camera with electronics made by Kodak.

Image quality of early consumer cameras was often 640×480 pixels or lower. Sensors were small and image quality no match for film cameras of the same period.

Enter the ‘Crop Factor’

The professional Kodak Digital DCS cameras first released 1991 introduced the concept of a ‘crop factor’. The sensors were not as large as the film they replaced within these cameras.  This meant the image captured did not cover the full area of the view finder, and was a ‘crop’ of the image which would have been captured with film.   The sensor for the camera ‘cropped’ the image captured by the lenses, retaining only the central section of the image.frontview

The kodak cameras were built using camera bodies from Nikon and Canon (and later medium format cameras), but adding a digital capture system using typically a 2 megapixel CCD (some later models reached 6 megapixels). Prices were as high as $25,000.  This was specialist technology!

The first Mainstream Digital DSLRs

In 1999 and 2000 Nikon and Canon respectively released far more mainstream digital SLR cameras to join those original models from Kodak.  However all of these cameras two things in common, they were all designed around 35mm camera systems and used exclusively 35mm lenses, but ‘cropped’ the 35mm image from the lens as they used sensors smaller than 35mm.

Digital Cameras in 2018 and beyond

The original digital interchangeable lens cameras were all designed around 35mm sensors, but now in 2018 we now have digital camera systems using:

  • smartphone cameras of 4.8×3.6mm (iPhone6)
  • 1/2.55 smartphone  5.6×4.2mm (iPhoneX, note8=1/2.4)
  • 1″ sensors 13.2×8.8mm
  • m4/3 sensors and lenses 17.3x13mm
  • APS/C sensors and lenses 22×14.8, 23.5×15.6 or 23.7×15.6
  • 35mm sensors and lenses 36x24mm
  • Crop Medium Format sensors of  44x33mm (Fuji)
  • Medium format lenses of 56x44mm
  • (Medium Format could be within the range 56×44-224 mm)

The leader in producing sensors for these various sensor sizes is Sony, and Sony concentrates technology for 35mm and smartphones.

The original meaning of Crop and Full Frame

Originally, and still today in most contexts in photography, to crop is to select an image from within a larger original image, and ‘full frame’ is to use the entire image.

As you can only crop if you have a larger image to start with, the only true ‘crop’ systems are those using lenses designed to accommodate a larger sensor than was used for the image.

So with a 35mm system lens on an APS-C camera, the camera will crop the image from the lens.  That is the lens is designed to produce an image of 36mm x 24mm, and the image captured is approximately 24mm x 16mm.  However, and  APS-C lens on an APS-C camera is using the entire image the lens is designed to produce, and is not cropping, and therefore is being used full frame.

APS-C cameras when used with full frame lenses (possible with Sony, Nikon and Canon, but not Fuji) and being used as cropped cameras, but all also have native APS-C lenses and these cameras are full frame for these lenses.

Similarly all current medium format cameras (Hasselblad, Pentax, Fuji) crop this image as they all use a smaller sensor than the medium format design.  It is reported here that the brand Zenit is preparing the first full frame medium format cameras.

So APS-C cameras when used with 35mm lenses and Medium Format Cameras are cropped, and others cameras are full frame.

The Evolved meaning of Crop Factor and Full Frame

The evolved meaning is to assume that every camera could be used with a 35mm lens, and the image cropped from that 35mm lens.

This meaning is useful for cameras up 35mm, but becomes quite strange above 35mm as it would suggest a cropped image medium format camera like the Fuji GFX 50s is actually beyond full frame (which of course is not really possible).

Full Frame: The evolved meaning is that ‘full-frame’ is 35mm, which means cameras from Fuji, Pentax, Hasselblad and Phase One are all ‘overfull’ or beyond full frame.

Crop Sensor: Any camera with a small sensor than 35mm is referred to as ‘crop sensor’, meaning large cropped sensors are not called ‘crop’ even though they do crop, and smaller sensor like smartphones which do not actually crop are called crop.

Crop Factor: The multiplier that should be applied to lens focal length to give as 35mm equivalent focal length.  Whether called ‘crop factor’ or more accurately ‘multiplier’, this is a very useful number.

Why the misleading terms?

The history

The first mass market interchangeable lens digital camera to capture the ‘full frame’ was a 35mm camera, the Canon 1DS.  For some years, the only digital camera to capture the same ‘full frame’ that film would capture, were 35mm cameras.

Further, while professional studio and fashion photographers mostly used the larger ‘medium format’ cameras,  consumers and newspaper and sports photographers used 35mm, the smallest format in wide usage at the time. The largest number of digital camera were a ‘crop’ of 35mm format, so the alternative for those cameras would be the full frame of 35mm format.

Digital photography disrupted the rules since as the sensor now came with the camera instead of being separately purchased and developed film, now any size sensor was possible and it was not just professionals dealing with differnt sizes, but also consumers.

New systems have since been released and generally these new systems use “full frame of an alternative size to 35mm”,  but, as the first cameras were actually a crop of 35mm, common practice became to quote the sensor size as if it was still a crop of 35mm.

Further, the need arose to compare effective lens magnification and apertures, even those these had traditionally been measured in film size specific ways.  Previously the most common system was 35mm, and the second most common was for professionals who lived cameras and had no difficulty converting.  Converting equivalence to 35mm became the standard for the all systems other than medium format, where people did not need to convert.

Rather unfortunately we kept the sensor size specific ways of specifying lens field of view (and debatably aperture) which means with so many different sensor sizes some conversion and equivalence is required.

Is it(using misleading terms) workable?

Yes, but only just, and perhaps not for long. Clearly the terms ‘crop’ and ‘full frame’ are now for most mirrorless systems misleading at best, and just crazy for sensors beyond 35mm.  However technology took a long time to deliver sensors of even 35mm, so sensors beyond 35mm are still relatively rare.  The other reason the terms work better than would be expected is that I would suggest the sensor market is currently dominated by Sony, and Sony focus their technology on three sensor sizes, 35mm, APC-C and camera-phone, and uniquely release their own mirrorless APC-C system using a full 35mm mount, and thus currently, produces the only crop 35mm mirrorless system.  (Canon produces the EOS-M system APS-C system, lenses for this mount can only be 35mm, as with the Fuji APS-C mirrorless system).

Unless the sensor market changes, beyond 35mm will remain rare and the misleading terminology will remain workable (if still misleading) in practice.  A future post will cover why the sensor market may indeed change!

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