Pentax smc DA 17-70 mm f/4.0 AL [IF] SDM review - Vignetting

Have you rated your lenses yet?

Pentax smc DA 17-70 mm f/4.0 AL [IF] SDM

10 June 2009

Arkadiusz Olech

8. Vignetting

Universal wideangle zooms with a big focal length range have usually a lot of problems with vignetting, which is especially visible at the ends of the range. Sigma 17-70 mm for instance, at the widest angle lost 40% of the corner illumination. So much praised Zeiss 16-80 mm had its biggest slip-up exactly in this category, losing 42% of illumination. Also the Nikkor 16-85 mm VR at 16 mm reached about 49% of illumination loss.

Compared to these performances, the Pentax 17-70 mm fares very well. At minimum focal length and maximum relative aperture the frame corner illumination loss is 29% (-1.0 EV) and, what is rare, at wideangle it decreases quickly on stopping down. By f/5.6 the vignetting is diminished to a convenient level of 15% and by f/8.0 it practically disappears (9%).

Pentax smc DA 17-70 mm f/4.0 AL [IF] SDM - Vignetting

Please Support Us

If you enjoy our reviews and articles, and you want us to continue our work please, support our website by donating through PayPal. The funds are going to be used for paying our editorial team, renting servers, and equipping our testing studio; only that way we will be able to continue providing you interesting content for free.

- - - - - - - - - - - - - - - - - advertisement - - - - - - - - - - - - - - - - -

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

To be honest with Sigma, we must note that at 17 mm that lens is faster than Pentax by 1 EV so it had a more difficult task when it comes to vignetting correction. On the other hand even if we stop it down to f/4.0 the vignetting still reaches 20% so the same level as with Pentax.

At 30 mm there are almost no vignetting problems. Even wide open Pentax has only a 12% (-0.36 EV) score which is very good and doesn’t bother at all. By f/5.6 the vignetting decrease to an imperceptible level of 9%.

At 50 mm and wide open the loss of frame corner illumination is 21% (-0.70 EV). Fortunately, on stopping down by one stop the problem disappears entirely (7%).

At maximum focal length the vignetting increases again and by f/4.0 it reaches 24% (-0.80 EV) but here also this aberration decreases quickly with stopping down, by f/5.6 dropping to 13 % and by f/8.0 – to 5%.

In this category Pentax undoubtedly can be only praised, having one of the best results in the universal zooms class.