Full frame lens on CMOS camera?

Discussion in 'Beginner Questions' started by ron_brown|6, Dec 10, 2011.

  1. Is there a lens I can put on a Canon CMOS to get a look of a full frame sensor? I was told that a 85mm 1.8 gives the same look on a small frame camera, as a full frame image.
    Does anyone know if there is a lens that gives a look as coming from a full frame camera? Thank you...
     
  2. Perhaps you are asking about angle of view on a full frame sensor camera, and want the same angle on a small sensor camera ?
    If you have a zoom lens, then you can use the zoom to achieve the same angle on both cameras by zooming in or out as appropriate. Otherwise, there is no such a lens.
     
  3. CMOS is a sensor type not a size/format. Your 400D has a "crop factor" of 1.6X as compared to a full frame sensor. For example, a 50mm lens on a 400D will give you the same field of view as an 80mm (50mm x 1.6) lens on full frame camera.
     
  4. A cheap way to own and try a full frame camera as much as you want is to get a film camera. Also, all the camera stores are willing to let you try and compare a full frame and a cropped sensor cameras with a same lens
     
  5. Is there a lens I can put on a Canon CMOS to get a look of a full frame sensor?​
    No and yes. You can get the equivalent angle of view by changing lenses, and that's about it.
    First, CMOS is a kind of sensor technology and has nothing to do with sensor size. The two kinds of sensors most widely used in digital photography are CCD (Charge Coupled Device) and CMOS (Complementary Metal Oxide Semiconductor). The smaller sensor is referred to as APS-C size, and is roughly 2/3 the surface area of a full-frame sensor. Full-frame is based on the dimensions of a 35mm film negative.
    Second, for technical reasons, a full-frame sensor (of equivalent sensor technology) will always out-perform a 'crop-frame' sensor in terms of noise, dynamic range, etc. That's strictly a function of physical sensor area available for the photosites, and has nothing to do with any lens.
    Third, because an APS-C sensor is smaller than a full-frame sensor, it 'sees' less of the image a lens projects to the inside rear of the camera. That effectively cuts down on the angle of view of a given lens, and is rather like cropping a print (hence the name 'crop-sensor'). The end effect is as if you used a lens with a longer focal length to take the shot. It is not magnification, and the focal length does not change, but the effective angle of view does change due to the smaller sensor.
    You can estimate and select a lens giving the equivalent angle of view of a given lens on a full-frame camera by multiplying the focal length of the lens by 1.6 (for Canon APS-C cameras; Nikon's APS-C 'crop factor' is 1.5). This is known colloquially as the 'crop factor'. Example: an 85mm lens on a Canon APS-C camera will give the angle of view of a 136mm lens with a full-frame camera (85mm x 1.6 = 136mm).
    More to your original question, to approximate the angle of view of a full-frame sensor DSLR, the lens of a 'crop frame' DSLR will need to be roughly 5/8 the focal length of that used on the full-frame camera. Example: to give the view of a 50mm lens with a full-frame camera, the focal length of a lens used with a crop-sensor camera would need to be 31.25mm (50mm/1.6 = 31.25mm, or 50mm x .625 = 31.25mm)
     
  6. Ron,
    There is a way of taking a shot on FF and a crop sensor that is identical and nobody can tell the difference. But not every shot taken with a FF can be replicated identically with crop cameras.
    The term you are looking for is equivalence. A shot taken with a crop camera with an 85 mm f1.2 at f1.4, 100 iso and 1/100 sec makes a picture that is identical in every respect to one shot with a FF camera and a 135 mm f2 at f2, 200 iso and 1/100 the sec. These images are identical in depth of field, noise, field of view etc and nobody can tell them apart.
    But shoot the FF with an 85 mm f1.2 at f1.2 and there isn't a lens made for crop cameras that will replicate that image, even the 50 f1 at f1 would look quite different.
    In the real world, if you shoot an 85mm f1.8 on a ff camera at f5.6 and 200iso, shoot the same thing with a crop camera with a 50mm f1.4 at f4 and 100 iso and again, nobody could tell them apart.
     

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