amfoto1 wrote:
It's actually quite a bit less than 1/2 the pixels on the FX sensor.
The AREA of a Nikon FX sensor is between 856 and 864 square millimeters.
The AREA of a Nikon DX sensor is between 368 and 370 sq. mm.
Divide the DX area by the FX area and you'll get between 42% and 43%.
So between 57 and 58% of an image is "cropped away". Or, in other words, when you crop FX down to DX you're left with around 42-43% of the original pixels.
42-43% of 24,000,000 is 10,080,000 to 10,320,000... or approx. 10MP.
By the way...
No, using an FX camera's DX setting or using an actual DX camera doesn't "extend a lens by 1.5X". 500mm is still 500mm, regardless.
However, when you crop the image to DX format that 500mm will "act like it's 1.5X more powerful, it will be roughly equal to what you'd see if you put a 750mm lens on a full frame camera". In fact, ALL lenses will "act" 1.5X longer than they would on full frame. That might be a good thing for telephotos, but a bad thing for wide angle lenses.
The crop doesn't change the focal length of the lens, it just changes the angle of view or field of view that's seen through any particular focal length. The angle or field of view of a 500mm lens on a DX camera will be about the same as the AoV/FoV of a 750mm on an FX camera. On an DX camera with the 3:2 aspect ratio common to all Nikon DLSRs (most DSLRs, in fact), the diagonal AoV/FoV of a 500mm lens is 3.3 degrees. On an FX camera the diagonal AoV/FoV of a 750mm lens would be the same 3.3 degrees. But if you instead but that 500mm lens on the FX camera, it's diagonal AoV/FoV will be 5 degrees.
It's actually quite a bit less than 1/2 the pixels... (
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Thanks. I see there is no upside.