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difference between APS -C sensor and CMOS sensor

Boris Activia , Apr 18, 2010; 02:59 a.m.

I'm confused, I'm reading about crop factor and the difference between a full frame sensor and APS - C sensor. Does a CMOS sensor have any relation to APS - C sensor?
I presume the APS - C sensor pertains to the Lens and APS - C sensor pertains to pixels.
I'm trying to understand the technical aspect of photography


Jean-Yves Mead , Apr 18, 2010; 03:11 a.m.

CMOS is a type of semiconductor, often used to make imaging sensors. APS-C is a standard size. They're not directly related.
CMOS would be compared to CCD, APS-C to 'full frame' and other sensor sizes.

Richard Snow , Apr 18, 2010; 09:11 a.m.


Here's a quick run down of information for you.


Full Frame = same size as a 35mm film frame
Examples of Full frame cameras are the Nikon D3/x/s, Nikon D700, Canon 1Ds Mk III, Canon 5D MkII, Sony a850, Sony a900

APS-C = same size as APS-C film. Approximately a 1.5x crop factor vs 35mm or Full Frame
Examples of APS-C Cameras: Nikon D300/s, Nikon D90, Nikon D5000, Sony a550, Sony a330

Canon's 1.6x crop sensor is close to the APS-C sensor size and they are commonly used interchangeably. Canon's 50D, T1i, T2i, and XSi use this format sensor

APS-H: Same size aS APS-H Film. Canon's 1.3x crop camera bodies are the only DSLRs that use this format. These include the EOS 1D Mark III and Mark IV.


CMOS and CCD are two different technologies used to capture images digitally. Both have their strengths and weaknesses. Most DSLRs are now using CMOS sensors exclusively.

Alan Marcus , Apr 18, 2010; 11:45 a.m.

The birth of 35mm film is the result of Thomas Edison bargaining with George Eastman (Kodak) for film for his Kinetoscope (first motion picture system 1889). Kodak was making roll film in 70mm width. The agreement was to supply this width. I was to be slit down the middle making two rolls each 35mm wide. Edison needs sprocket holes on each side to transport the film in his movie camera. The space between the sprocket holes allowed an image 24mm wide. The film travel was vertical; the height of the image was set to 18mm. For years the standard for motion pictures was 24mm by 18mm.

Soon the motion picture industry flourished. Film in 35mm width was widely available. Ernst Leitz (German 1871-1956) Owned the Leitz optical works in Wetzar. His chief engineer Oskar Barmack invented a still camera around the 35mm sprocketed film. This camera, the Leica, utilized horizontal film travel. The 18mm image height was doubled to 36mm. This was the birth of the full frame 24 by 36mm image. The Leica was manufactured in 1924.

The full frame 24mm by 36mm has been challenged many times. Keep in mind that format size popularity is based mainly on advances in film science. A meaningful challenge came in 1996 when Kodak headed a consortium (Kodak - Fuji - Konica - Nikon -others) to make a still camera utilizing 24mm film. The idea revolved around motion picture film that was over coated with a transparent magnetic coat designed to carry the sound track. The idea was a hybrid camera with film that carried both a chemical and a digital image. The classification was Advanced Photo System or APS for short.

The information recorded by the camera on the film signaled the photofinisher as to how to print the images. Thus the 24mm wide film had three aspect ratios. H for High Definition 16:9 (same as today's HD TV's - C for Classic format 16mm x 24mm ratio 1.5 (same as 4x6 print). P for Panoramic 4 x 11 prints.

The APS System was a failure mainly because the 35mm cameras of the day were advancing due to onboard chip logic and the introduction of the digital camera.

As the digital's came on the scene, most utilized a full frame sensor borrowed from 35mm still camera design i.e. 24mm by 36mm.

Improvement in sensor chip technology allows leads to smaller and smaller sensors. Many are manufactured using the APS-C dimensions 16mm by 24mm.

The CCD (Charged Coupled Device) has on its surface, photosites in a grid pattern. Each sight consists of a photodiode to capture light and storage area to hold the electric charge generated by a photon hit. The charge is moved out of the photosites into another chip for processing into an image.

The CMOS (Complementary Metal Oxide Semiconductor) consists of photosites and an area in the chip to process the signals into an image. Thus the CMOS saves power and processes the data faster.

The CCD requires additional chips and consumes more power. Because the CCD must move charges around, it takes more time to assemble an image.

Future chips will be much much smaller as technology marches on.

Dan Ferrel , Apr 18, 2010; 02:24 p.m.

OK Boris, you've received some good and accurate answers here so far. So let me just throw in my "layman's terms" take on it all.

CMOS and CCD do pretty much the same thing, capture an image. Let the manufacturers hash it out as to which is best.
APS-C, APS-H, and full frame all refer to a crop factor, but what does it mean to you? If you're coming from a background in photography and you know what a 24mm lens will capture (angle of view) on a regular film or full frame camera then by attaching that lens to an APS sensor camera you now lose some of the outside of that image. But since it's still printed at the same size as you've printed for years before it's essentially like you've just cropped the image and enlarged it back to what you're used too.
But if you don't know what your lens is supposed to look like, then you have no point of reference at all. It could all be a foreign language written on the lens and it would make as much sense. You get a general idea that 24mm is a wider lens than a 50mm, but unless you're used to what 24 and 50 look like in the viewfinder it's all just numbers.

In the end, put the lens on the camera and see for yourself what you see. That's what you'll get.
You may also have a look at http://www.fredparker.com/vislize.htm to give yourself a visual of what to expect.

Tim Lookingbill , Apr 18, 2010; 02:59 p.m.

According to wikipedia the difference between a CCD and CMOS is that CMOS is less expensive to manufacture because it requires fewer parts, requires less energy and directly converts light energy to voltage where as CCD's hold a charge and then converts it to voltage readouts one pixel at a time making CMOS sensors a bit faster at capturing and converting light energy.

Steven Altman , Aug 18, 2014; 09:45 a.m.

OK. Thanks for the technical jargon. It is quite useful. Now the question is, which sensor produces the higher quality image? Which manufacturer produces the best sensor ?

Rob Bernhard , Aug 18, 2014; 10:20 a.m.

[[which sensor produces the higher quality image? Which manufacturer produces the best sensor ?]]

There is no answer to this question. Arguments for or against one sensor manufacturer or another are heavily biased. Pure numbers-based measurements presented by certain websites do not accurately reflect real-world shooting results.

You can only buy a camera system that meets your needs. Concentrating on sensors only could result in a wrong choice if the system you buy is missing components/lenses/etc. critical to your type of photography.

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