To compare real-life performance we shot the
same scene with the Sony 75-300mm and Sony 18-70mm using the Sony Alpha A100 within
a few moments of each other using the camera's best quality JPEG and lowest ISO settings.
We set the 75-300mm to 75mm and the 18-70mm to 70mm for the closest match, although the former will of course produce a slightly smaller field. We also acknowledge we're comparing the wide-end of one lens against the long end of another, but it still illustrates any optical differences when switching from one range to the next.
The image above was taken with the Sony 75-300mm at 75mm f9 using the Sony A100 body at a sensitivity of 100 ISO; the original JPEG measured 2.76MB. Apertures of f8 were selected for optimum sharpness with each lens. The
crops are taken from the upper left, center and lower right portions of the originals.
The three crops below exhibit very similar degrees of detail and at first glance there's little to differentiate them. At closer examination though, even with just 5mm longer focal length, the 75-300mm is delivering tighter crops allowing greater separation of lines, but there's arguably slightly greater detail in the 18-70mm samples. As our technical resolution results show on the next page, the 18-70mm at 70mm out-performs the 75-300mm at 75mm, so if you're shooting around this focal length, you'll get a better result with the shorter lens, but as this page shows, it's still pretty close.
