Remember that the focal length required to produce a specific angle of view with an APS-C or Four Thirds System D-SLR will be shorter than that needed to produce the same angle of view with a 35mm SLR or full-frame D-SLR. The specs for each D-SLR note the sensor’s focal-length factor, a figure that tells how its images relate to those of a 35mm film frame. For example, Nikon’s non-full-frame D-SLRs (all except the D3, D3X and D700) have a factor of 1.5x—any given lens used on one of those D-SLRs will frame like a lens 1.5 times longer on a 35mm SLR (or full-frame D-SLR). For example, put a 100mm lens on a D300, and it will frame like a 150mm lens on a full-frame D3.
Here are the magnification factors for popular D-SLRs:
• Canon: 1.6x for all but the EOS 5D and EOS-1 series pro models
• Canon EOS-1D series: 1.3x
• Canon EOS-1Ds series and EOS 5D/ EOS 5D Mark II: 1x (full-frame)
• Fujifilm: 1.5x for all D-SLRs
• Nikon: 1.5x for all but the full-frame D3, D3X and D700
• Olympus: 2x for all D-SLR models
• Panasonic: 2x for all D-SLR models
• Pentax: 1.5x for all D-SLR models
• Samsung: 1.5x for all D-SLR models
• Sigma: 1.7x for all D-SLR models
• Sony: 1.5x for all D-SLR models but the full-frame DSLR-A900
Pro Lenses And Image Quality
The right focal lengths provide you with the needed angles of view, but there’s more to consider than just angle of view.
Most pros shoot with pro lenses. Pro lenses cost more and are heavier, but they’re also sharper, better corrected for aberrations and distortion, and generally can stand up to outdoor conditions better. Pro lenses are also generally faster, which means you can shoot in dimmer light, at lower ISOs or at faster shutter speeds. This, in turn, means you can get shots that photographers using slower lenses can’t get. Pro lenses also provides quicker, more accurate autofocusing performance, important for wildlife-action photography.
If your budget doesn’t allow for pro lenses, you can get the same angles of view with lower-priced lenses, and some very good shots. But image quality won’t be quite as good as if a pro lens had been used to shoot the same images.