To measure lens vignetting and light fall-off we photographed a white target with a highly diffused filter. The lenses were tested with their apertures wide open using a Pentax K10D in Aperture Priority mode; the DA 18-55mm was tested at both 18 and 55mm focal lengths. The images were analysed with Imatest and the full areas presented here at a reduced resolution. Bigger percentages are better.

Using the Pentax 40 and 70mm lenses with their apertures wide open sees the light fall-off in the corners to 70.2 and 73.2% of the centre measurement respectively. These are good results considering their maximum apertures, but nothing remarkable. It's interesting to note the kit lens zoomed-into 55mm delivers less light fall-off, albeit with a far less impressive maximum aperture.