Lens review

Pentax smc DA 70 mm f/2.4 Limited

8. Vignetting

Small dimensions of lenses often entail problems with vignetting. Unfortunately, the Pentax 2.4/70 didn’t avoid them. When wide open, the frame corners light fall-off amounts to as much as 30% (-1.05 EV). Certainly it is nothing to be proud of. On stopping down to f/2.8 the problem decreases to 24%. Further stopping down improves the situation significantly because by f/4.0 we have 12 % of brightness loss and by f/5.6 - only 9% so the value we consider, in fact, imperceptible.

As the lens hood, included in box, seems to be rather high in comparison to the whole lens especially when screwed out, we decided to test whether it has any influence on vignetting level. After putting it on the brightness loss in the corners increased by 1% on average so a value that could be deemed negligible.