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Lens review

Pentax smc FA 77 mm f/1.8 Limited

22 September 2009
Szymon Starczewski

8. Vignetting

On the one hand the Pentax 1.8/77 is designed to work on full frame so a small APS-C sensor of a Pentax K20D shouldn’t be a problem when it comes to vignetting. On the other hand, though, with such small physical dimensions and such parameters the lens might be supposed to have a slip-up in this category.

Pentax smc FA 77 mm f/1.8 Limited - Vignetting


Before we find out how it fared in reality let’s remind ourselves that the Nikkor 1.8/85 performed very well here, with the light fall-off in the corners of only 15%. The Canon was a bit worse with the result of 22%. The Pentax’s performance is similar to that of the Canon as it loses 22% of light (-0.72 EV) in the frame corners. This result doesn’t improve on stopping down to f/2.0 because the light fall-off is still 21%. Fortunately by f/2.8 the problem disappears with the marginal result of 4%.

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Pentax smc FA 77 mm f/1.8 Limited - Vignetting