QUOTE(pac1 @ Nov 16 2007, 01:38 PM)
Nikon DX is 1.5, 1.6 is Canon.
The effective focal length of a lens depends on the crop factor of the camera sensor.
For example Sigma 12-24mm EX lens:
- when use on full frame DSLR, you'll have the same focal length of 12mm - 24mm.
- when use on Nikon's camera, you'll have to multiply with the crop factor of 1.5, you'll have 18mm - 36mm focal length
- when use on Canon's camera, you'll have to multiply with 1.6, you'll have 19.2mm - 38.4mm.
The table below that shows the equivalent lens sizes for different crop factors. The column on the left is the lens focal length on a full frame camera.

Full frame - Canon 5D/1D MkIII, Nikon D3
1.3x - Canon EOS 1D/1D MkIIN
1.5x - Nikon D40/D50/D70/D70s/D80/D200/D300/D2XD2Hs, Minolta 7D/Fuji S3 Pro, Pentax *istDS/K100D/K110D/K10D
1.6x - Canon EOS 300D/400D/20D/30D/40D
2.0x - Olympus E-400/E-500/E-300/E-1
tks for the info...yeah, I did realised the difference comparing with my dad's 1975-80s' Canon SLR using the 70-210 F4 lens...The effective focal length of a lens depends on the crop factor of the camera sensor.
For example Sigma 12-24mm EX lens:
- when use on full frame DSLR, you'll have the same focal length of 12mm - 24mm.
- when use on Nikon's camera, you'll have to multiply with the crop factor of 1.5, you'll have 18mm - 36mm focal length
- when use on Canon's camera, you'll have to multiply with 1.6, you'll have 19.2mm - 38.4mm.
The table below that shows the equivalent lens sizes for different crop factors. The column on the left is the lens focal length on a full frame camera.

Full frame - Canon 5D/1D MkIII, Nikon D3
1.3x - Canon EOS 1D/1D MkIIN
1.5x - Nikon D40/D50/D70/D70s/D80/D200/D300/D2XD2Hs, Minolta 7D/Fuji S3 Pro, Pentax *istDS/K100D/K110D/K10D
1.6x - Canon EOS 300D/400D/20D/30D/40D
2.0x - Olympus E-400/E-500/E-300/E-1
Nov 16 2007, 07:33 PM

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