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07-17-2010, 05:30 AM   #1
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question on WR 50-200mm/2 Q's

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Last edited by TheoSixx; 07-19-2010 at 08:13 AM. Reason: *****
07-17-2010, 05:35 AM   #2
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50x1.5 = 75
200x1.5 = 300

Looks like you multiplied your numbers twice or multiplied instead of dividing!

If you want to calculate FOV, you multiply the focal length by 1.5 when going from APS-C to Full-Frame, and divide by 1.5 when going from Full-Frame to APS-C. Keep in mind that a 200mm lens is always a 200mm lens, however, and that the calculations above are only to show what focal length on a FF body would result in the same FOV on APS-C.

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07-18-2010, 08:06 AM   #3
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Hello,

Focal length causes so much confusion today, due in part I believe because 35mm film cameras evolved into digital. The issue has always been around, but in the past, we all just accepted that an 80mm lens was a normal (50mm) lens on a Hasselblad.


The first is the technical description of the optical formula used in the lens design.

Focal length is defined as the distance between the film or sensor area (known as the focal plane) and the optical center or nodal point of a lens focused at infinity. So a 50mm lens’s optical center would be 50mm’s from the film or sensor plane at infinity.

The second is our interpretation of what the lens will do for us while photographing.

We describe a 50mm lens as being a normal lens. “Normal” lenses have focal lengths approximately equal to the diagonal length of the film or sensor area. The diagonal length of 35mm film is 42mm’s. Normal lens have an angle of coverage of approximately 46 degrees, which corresponds to our own vision.

The lens multiplier formula used today is method for understanding how a lens will perform on a digital camera ( with a sensor smaller than a 35mm film frame ) in terms of what we were accustomed to when shooting film. Whether on an APS-C sensor, Full Frame or 35mm film body, a 50mm lens is a 50mm lens. How it affects our image is another matter.


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Last edited by Chuck-B&H; 07-18-2010 at 08:07 AM. Reason: Spacing
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