Monday, 15 February 2016

Other than speed and weight, what advantages might a prime lens have over a zoom at the same focal length?


At the same focal length, apart from speed and maybe weight, what other advantages does a prime lens like the 50mm have over a zoom lens like the 24 - 70mm?


To put it better, If I set my 24-70mm lens at 50mm and I don’t care about length and speed, what advantage would just using the 50mm offer me over the 24-70mm



Answer



A prime likely still has several advantages over a zoom at a given focal length. (Well, depending upon your needs and habits.)





  • A less complex optical design. All else being equal, a less complex design is likely to have fewer compromises, which means the prime is more likely to have less distortion of any sort -- pincushion, barrel, coma, and chromatic abberations. And on the flip side, a sharper lens.




  • Maximum aperture: an f1.4 prime is two stops faster than a "pro" f2.8 lens. 3 stops faster than a consumer-aimed f4. That lets you use a shallower depth of field and see in dim light much more easily.




  • Focus speed: a less complex design almost definitely means less weight to move to bring the lens in focus and a larger aperture lets in more light to make focus more sure-footed, so the focus speed can be faster.





  • I wasn't sure what you meant by "speed." Focus speed or aperture speed? I covered those. Here's one more: composition speed. With a prime I don't need to twist the zoom ring to get to 50mm -- I'm always there!




  • When comparing to a consumer lens, the prime also typically has a focus scale and a much smoother focus ring (with a longer throw, too).




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